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JAVA EE DEVELOPMENT (JSP and Servlets)

Talha Ocakçı
Talha Ocakçı

The document provides a comprehensive overview of using JSP and Servlets for developing web applications using the client-server model, emphasizing the roles of HTTP methods and application servers like Apache Tomcat. It details how JSP pages and Servlets interact, the structure and management of sessions, and covers database integration with SQL principles, focusing on relational database systems, transactions, and best practices for J2EE development. Additionally, it discusses database design principles, user role management, and the significance of connection pooling in database operations.

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JSP and SERVLET Creating Web Applications by www.javathlon.com
www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
www.javathlon.com HTTP PROTOCOL STANDART BEHAVIOURS ● GET method Ask server for a resource via a URI (HTML page, image, MP3 etc) ● POST method Sent a web form to server and get a resource ● Other methods HEAD, PUT, DELETE, TRACE
www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
www.javathlon.com Client - Server Web Applications CLIENT HTTP PROTOCOL JSP PAGE PROCESSING UNIT (SERVLET) PROCESSING UNIT (SERVLET) SERVER PROCESSING UNIT (SERVLET) DATABASE
www.javathlon.com NEED FOR APPLICATION SERVERS ● Dispatch requests ● Thread management ● Session management ● Caching and object pooling We will use APACHE TOMCAT
www.javathlon.com Reminders How a J2EE project runs? ● Client side consists of JSP pages. A JSP is an HTML page with special tags to get or send dynamic data from/to server. ● Servlets carry business code on server side and redirects the client to proper pages as result. ● JSPs and servlets communicate via HTTP protocol. Mostly GET and POST methods.
www.javathlon.com Reminders How a J2EE project runs? JSP and servlets are contained in web application servers ( servlet containers) such as Apache Tomcat. We develop configuration files such as web. xml to regulate interactions among JSPs, servlets and other resources.
www.javathlon.com TECHNOLOGY STACK Programming IDE Servlet Container (Application server) Java Runtime Environment 6
www.javathlon.com SERVLET MECHANISM SERVLET Http Servlet Request Return an HTML content Return a multimedia file Redirect the client to a page Forward request to another servlet Get or Post Method
www.javathlon.com HTTPSERVLETREQUEST GET method POST method SERVLET When you enter a web address to a web browser, it requests the resource by GET method. The request body is limited to about 250 characters. Sample:https://www.google.com.tr/?q=java&safe=off&output=search You need to send a web form for using POST method. The request body is limitless
www.javathlon.com HTTPSERVLETRESPONSE Talha Ocakci Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
www.javathlon.com HTTPSERVLETRESPONSE Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
www.javathlon.com SCRIPTLET in JSP A scriptlet is a piece of Java-code embedded in the HTML. The scriptlet is everything inside the <% %> tags. Between these the user can add any valid Scriplet i.e. any valid Java Code.
www.javathlon.com IMPLICIT OBJECTS in JSP They are the objects that you can use inside scriptlets application javax.servlet.ServletContext out javax.servlet.jsp.JspWriter request javax.servlet.ServletRequest response javax.servlet.ServletResponse session javax.servlet.http.HttpSession page java.lang.Object servletconfig javax.servlet.ServletConfig
www.javathlon.com OBJECT SCOPES in SERVLETCONTEXT Application Scope Request Scope Session scope
www.javathlon.com HTTP SESSION OBJECT SESSION ID Session object Attribute map name1 value1 name2 value2
www.javathlon.com HTTPSERVLETRESPONSE Talha Ocakci Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
www.javathlon.com REDIRECTING REQUEST Request forwarding and redirection are different concepts. When you forward a request, request and response objects are transferred. Url stays the same. When you redirect the request to another JSP/servlet, request and response objects are not transferred to new object. URL changes to the directory of new page.
www.javathlon.com Tip for being a wanted J2EE developer ● Avoid using JAVA code inside a JSP file. Use JSP directives and JSP actions instead. ● Avoid using HTML code inside a servlet. Instead, use HTML code in JSP page and pass values it from the servlet.
www.javathlon.com JSP Actions ● jsp:useBean Searches for an objects inside the given scope ● jsp:getProperty ● jsp:setProperty Gets/sets a value of a given object
www.javathlon.com jsp:useBean action <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInfo" scope="request"> </jsp:useBean> request.getParameter(“memberInfo”) <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInfo scope="session"> </jsp:useBean> request.getSession().getParameter(“memberInfo”) <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInf scope="application"> </jsp:useBean> ServletContext sc = getServletContext(); sc.getAttribute(“memberInfo”)
www.javathlon.com jsp:getProperty and jsp:setProperty Gets/sets an attribute of an object with a given id
www.javathlon.com JSTL BASICS Java Server Tag Library Provides shorthand notation to access: ● Attributes of standard servlet objects ● Bean properties We use them, because writing JAVA code inside JSP is not a good practice. It is a third party library of Apache Foundation.
www.javathlon.com JSTL and JAVA Code Relation Iterating over a list JAVA NOTATION <ul> <% for(int i=0; i<messages.length; i++) { String message = messages[i]; %> <li><%= message %></li> <% } %> </ul> JSTL NOTATION <ul> <c:forEach var="message” items="${messages}"> <li>${message}</li> </c:forEach> </li>
www.javathlon.com FULL LIST OF JSTL TAGS
www.javathlon.com CLUE WEB APPLICATION WEB BROWSER ask for sth show result
www.javathlon.com CLUE A basic web application is nothing more than a system that populates data from a database, insert into it, modify the data and visualize it. USER INTERFACE DATABASE WEB APPLICATION sends input select delete & update insert shows result
www.javathlon.com WORKING WITH DATABASE Description A database is any file or file system that you can ● store your data ● manipulate data ● search for a desired item
www.javathlon.com WORKING WITH DATABASE Database Types ● Flat files (text or binary) ● Flat file systems ● Non - relational databases (eg. MongoDB) ● Relational databases (eg. MySQL)
www.javathlon.com WORKING WITH DATABASE Why use RDBMS? Relational Database Systems: Ease your tasks for quickly inserting, updating, querying, deleting the data you have on your hands using SQL.
www.javathlon.com WORKING WITH DATABASE Relational Databases Relational Database Systems: Stores the data in tables and relations between those tables.
www.javathlon.com WORKING WITH DATABASE Relational Database Structure Table: A real world or imaginary entity model that has attributes. (A user metadata) Row: An instance of a entity model (A user instance) Column: Attribute of an entity (User’s name) Primary key: Identifier of a instance (User’s id) Foreign key: Dependency of an entity to another entity (Reference to user’s question)
WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Tables and columns Keep track of all money transfers in a bank. You need to store this data permanently. ROW 1 ROW 2 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Date 1.1.2014 Sender name Kirk Sender surname Hammett Sender account no 565656565 Receiver name James Receiver surname Hetfield Receiver account no 808080801 Amount 50000 Currency USD Date 3.1.2014 attribute value DB TABLE (MONEY TRANSFER)
www.javathlon.com SQL (Structured Query Language) ● DDL (Data Definition Language) Used to create or modify tables, data types of columns ● DML (Data Manipulation Language) Used to insert, update, delete data and query for desired data
www.javathlon.com DATA TYPES ● String types ● Numeric types ● Date & Time types ● Binary objects
www.javathlon.com WORKING WITH RELATIONAL DATABASES Creating table structures Done with DDL (Data Definition Language ) CREATE TABLE money_transfer( transfer_id INTEGER PRIMARY KEY, sender_name VARCHAR(50) NULL, sender_surname VARCHAR(50) NULL, sender_surname VARCHAR(50) NULL, sender_account_no VARCHAR(20) NULL, receiver_name VARCHAR(50) NULL, receiver_surname VARCHAR(50) NULL, receiver_account_no VARCHAR(50) NULL, amount FLOAT; currenct VARCHAR(4) NULL, transfer_date DATE NULL ); Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Transfer Date 1.1.2014
WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Breaking the data into smaller units Multiple similar records means lots of repetition and repetition means mess. For preventing the repetition, we break the data into multiple columns. Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Date 1.1.2014 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name George Receiver surname Harrison Receiver account no 12045872 Amount 400 Currency USD Date 1.2.2014 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Ringo Receiver surname Start Receiver account no 13698985 Amount 500 Currency USD Date 1.3.2014
WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Data normalization ● Basic client data is extracted from the money transfer information. ● Client data is stored in another table. Identifier of the record inside client table is referenced from money transfer table Sender Client data 121 Receiver name George Receiver surname Harrison Receiver account no 12045872 Amount 400 Currency USD Date 1.2.2014 Sender Client data 121 Receiver name Ringo Receiver surname Starr Receiver account no 13698985 Amount 500 Currency USD Date 1.3.2014 Client data Client id 121 Client name John Client surname Lennon Client account no 79879878978 Client id( Foreign key)
www.javathlon.com Tip for being a wanted J2EE developer A database table SHOULD correspond to at least one real world or virtual entity. DATABASE TABLE DESIGN PRINCIPLES 1
www.javathlon.com Tip for being a wanted J2EE developer 2 Dependent entities should reference to the owner entity for data integration. DATABASE TABLE DESIGN PRINCIPLES
www.javathlon.com DATABASE DESIGN for the USER MANAGEMENT MODULE of QA PLATFORM
www.javathlon.com REGISTRATION Insert a user with ● username, ● password ● and other personal details.
www.javathlon.com AUTHENTICATION Check if given username-password pair exists in database.
www.javathlon.com REGISTRATION DB SCHEMA STANDART MUST-DOs 1. Put a primary key. 2. Put insertion date, 3. Put active/passive bit BUSINESS SPECIFIC 1. Store username and password 2. Store personal details
www.javathlon.com REGISTRATION CREATE TABLE CREATE TABLE `user` ( `user_id` int(11) NOT NULL, `user_name` varchar(45) DEFAULT NULL, `password` varchar(45) COLLATE DEFAULT NULL, `is_active` bit(1) DEFAULT NULL, `name` varchar(45) DEFAULT NULL, `surname` varchar(45) DEFAULT NULL, `insert_date` datetime DEFAULT NULL, `role_name` varchar(45) DEFAULT NULL, PRIMARY KEY (`user_id`) )
A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com with SQL Insert data INSERT INTO TABLENAME (first_column,...last_column) VALUES (first_value,...last_value); INSERT INTO user (user_id, user_name, password) VALUES (1, 'paul_weller','hzf1234fddf')
A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com with SQL Primary key insert into user (user_id, user_name, password) values(100, 'paul_weller','hzf1234fddf') Error Code: 1062. Duplicate entry '100' for key 'PRIMARY' 0.000 sec Each table HAS TO have a primary key. This lets your database vendor to allocate unique space for each record in any tables. insert into user ( user_name, password) values ('eddie_vedder','hzf1234fddf'); Each table HAS TO have a primary key. This lets your database vendor to allocate unique space for each record in any tables. You will see user_id column gets unique values one by one.
www.javathlon.com A PRIMER FOR DATA MANIPULATION with SQL Update a record update TABLENAME set COLUMNNAME = VALUE update user set user_name= ‘hgklkg45784’
www.javathlon.com A PRIMER FOR DATA RETRIEVAL with SQL Retrieve all records DO NOT use * in select clauses. Using * is a good example of cutting corners that junior developers do. Define which columns you exactly need and want to populate.
A PRIMER FOR DATA RETRIEVAL wwwwi.jtavhath lon.com SQL Restrict records select COLUMN1,COLUMN2 from TABLENAME where COLUMN1 = VALUE and/or COLUMN2 = VALUE2 select user_name from user where user_name =’'paul_weller'’ and password = ‘'hzf1234fddf'’
www.javathlon.com IN NEXT CHAPTER ● Database Connections ● Transactions ● What is ACID? ● Committing and rolling the transactions back ● DB Engine - Java communication
www.javathlon.com DATABASE CONNECTIONS Database connection is the means by which a database server and its client software communicate with each other.
www.javathlon.com WHY WE NEED DATABASE CONNECTIONS? We send the commands to DB server and get the results via an open DB connection. DB SERVER Java web application DB CONNECTION
www.javathlon.com COMMUNICATION BETWEEN JAVA AND DATABASE Database talks SQL, but Java does not know how to talk in SQL, it needs a translator called JDBC (Java Database Connector).
www.javathlon.com DB CONNECTION POOLS DB connection opening and closing is so expensive operations compared to execute basic queries. Instead of open/close a connection for each query, create a bunch of connections* and use them over and over again. * = Connection pool
www.javathlon.com DB CONNECTION POOL USAGE
www.javathlon.com CONNECTION POOL Implementations in Java ● C3P0 ● BoneCP ...
www.javathlon.com DATABASE TRANSACTIONS A unit of work performed within a database management system against a database.
www.javathlon.com DATABASE TRANSACTIONS ALL OR NOTHING PRINCIPLE 1. Open connection 2. Begin transaction 3. Debit $100 to Groceries Expense Account 4. Credit $100 to Checking Account 5. Commit transaction 6. Close connection TRANSACTION
www.javathlon.com ACID Properties that a transaction must have Atomicity: Based on “all or nothing” principle All statements succeed or all fail in case of any power failures, errors, and crashes.
www.javathlon.com ACID Properties that a transaction must have Consistency: If, for some reason (eq: programming error), a transaction is executed that violates the database’s consistency rules, the entire transaction will be rolled back and the database will be restored to a state consistent with those rules. eq: NULL inserting to a not-nullable column
www.javathlon.com ACID Properties that a transaction must have Isolation: Before committing a transaction, modifications should not be visible to another transaction.
www.javathlon.com ACID Properties that a transaction must have Durability: Durability guarantees that the database will keep track of pending changes in such a way that the server can recover from an abnormal termination.
www.javathlon.com DATABASE DESIGN for the USER ROLE MANAGEMENT MODULE
www.javathlon.com User Role- Permissions Logic MODERATOR MODIFY POST DELETE POST CREATE POST USER 1 USER 2
www.javathlon.com User Role- Permissions Logic Required permissions: 1- Deleting posts 2- Correcting posts Required permissions: 1- Accepting new users 2- Deleting users John Hopkins is a moderator. A moderator has permissions for 1- Deleting posts 2- Correcting posts
www.javathlon.com Tip for being a wanted J2EE developer Why not assign the permissions directly to the user but assign to a role? Because adding or removing the permissions to a role, lets the system grant or revoke this permission from all the users who belong to this role. Otherwise you would execute this modification on all users and this means a huge cost.
www.javathlon.com Requirements: ● TABLE RELATIONS (1 to MANY, MANY to 1, MANY to MANY) ● SQL JOINS (inner join, left join, right join, full join, self join)
www.javathlon.com THE MEANING OF RELATIONAL in RELATIONAL DATABASES One object may belong to how many other owner objects? One object may own to how many other dependent objects?
www.javathlon.com TABLE RELATIONS ONE TO ONE USER USER-DETAILS (Country, Height, Weight ...) If you safely can add the columns in one table to another relation means 1-1.
www.javathlon.com TABLE RELATIONS ONE TO ONE OPTION 1 USER TABLE USER ID USER NAME COUNTRY REGISTRATION DATE HEIGHT WEIGHT TIMEZONE USER TABLE USER ID USER NAME REGISTRATION DATE USER DETAILS TABLE USER ID HEIGHT WEIGHT COUNTRY OPTION 2
www.javathlon.com TABLE RELATIONS ONE TO MANY ONE MANY QUESTION ANSWER 1 ● A question may own two answers. ● But, an answer can not be given two multiple questions. ANSWER 2 QUESTION ANSWER 3
www.javathlon.com TABLE RELATIONS MANY TO MANY MANY MANY USER TOPIC 1 ● A user may follow multiple topics ● A topic may be followed by multiple users. TOPIC 2 USER TOPIC 3
www.javathlon.com TABLE RELATIONS MANY TO MANY USER TABLE USER ID USER NAME USER NICKNAME 1 Talha Ocakçı talhaocakci 2 James Dio dio TOPIC TABLE TOPIC ID TOPIC NAME 1 Geography 2 History USER FOLLOWED TOPICS USER ID TOPIC ID FOLLOW TIME 1 1 10.06.2014 2 1 18.06.2014 2 2 18.07.2014
www.javathlon.com JOINING TABLES To retrieve and combine different attributes of an entity from several tables. SELECT CLAUSE + FROM CLAUSE + JOIN CLAUSE (multiple) + WHERE CLAUSE +
www.javathlon.com JOINING TABLES Inner Join Both tables must have the same value on joined columns. eq. Populate list of permissions that a user has.
www.javathlon.com JOINING TABLES Left (Outer) Join If a row in table 1 does not have a match in table 2, it still exists in result set.
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IMPLEMENTING JAVA WEB APPLICATION
www.javathlon.com WHAT WE WILL DO? 1. Without caring of user interface design, focus on the technical details. 2. Find the most time consuming phases in development and ease them professionally
www.javathlon.com REGISTER USER Get username, email, name, surname of user and post it to servlet JSP 1. Get values from request 2. Get DB connection (Create or get one from DB connection pool) 3. Start transaction 4. Insert user to DB 5. Release all resources 6. Put message into response 6. Redirect to another page SERVLET Show the message inside JSP
www.javathlon.com JDBC CLASSES Statement ● Contains a static SQL statement ● Not reusable PreparedStatement: ● Contains precompiled SQL statement. ● Used to efficiently execute this statement multiple times by just setting parameters.
www.javathlon.com JDBC CLASSES ResultSet Holds the database result row by row Holds the metadata of the DB result (count, column names, etc)
www.javathlon.com JAVA - MYSQL TYPE CORRESPONDENCE
www.javathlon.com RESULT SET OBJECT VALUES METADATA talha ocakci talhaocakci paul auster paulauster ... ... ... Count Column types Schema name Table name ... POINTER
www.javathlon.com RESULT SET OBJECT resultset.next() method moves the pointer to next row. If reaches to the end it returns false. talha ocakci talhaocakci paul auster paulauster ... ... ... POINTER Initially, it points to the very beginning of the ResultSet object but not the first row. To get the first row, you need to invoke next() before iterating.
www.javathlon.com REGISTER USER Get username, email, name, surname of user and post it to servlet JSP 1. Get values from request 2. Get DB connection (Create or get one from DB connection pool) 3. Start transaction 4. Insert user to DB 5. Release all resources 6. Put message into response 6. Redirect to another page SERVLET Show the message inside JSP
www.javathlon.com CONNECTION POOLS Created on servlet containers (Tomcat 7) or application servers (JBOSS, Glassfish, etc..) and can be access by JNDI Created with C3P0 independent from a servlet container or an application server.
www.javathlon.com CONNECTION POOLS Configuration Min connection size: Whatever happens, connection number will not drop below this. Max connection: Number of connection can not exceed this number. Timeout: If idle time of a connection exceeds this time, it returns back to pool automatically.
www.javathlon.com INITIALIZE RESOURCE WHILE BOOTSTRAPPING ● Mark your servlet for automatic invoking while bootstrapping the application in deployment descriptor. marker: load-on-startup tag. ● Initialize resources in init() method of servlet.
www.javathlon.com EMAIL VALIDATION 1- Insert the new user record to user table 2- Insert a related record to email-validation table including user id and validation code. 3- Email the validation url including the validation code to user’s email. 4- When sent link is clicked, check the validation code in url against the one in DB.
www.javathlon.com EMAIL VALIDATION When a connection is created, it is in auto-commit mode. The way to allow two or more statements to be grouped into a transaction is to disable the auto-commit mode.
www.javathlon.com GET GENERATED KEYS preparedStatement.getGeneratedKeys() returns a Result Set with one column and one row: POINTER VALUES 29
www.javathlon.com WORKING IN PROFESSIONAL SOFTWARE DEVELOPMENT TEAMS
www.javathlon.com WORKING IN A TEAM If team members use; ● Different approaches to similar problems ● Different relations between software layers... There will be chaos later on.
www.javathlon.com WORKING IN PROFESSIONAL SOFTWARE DEVELOPMENT TEAMS Why do we use design patterns? Developers agree on the best solutions and apply them for similar problems.
www.javathlon.com SOFTWARE ARCHITECTURE AND DESIGN PATTERNS Design patterns ensure the project will not fail by the time passing. If you don’t obey the rules, the failure underneath will be observed.
www.javathlon.com DESIGN PATTERN and STRATEGY Design Pattern: Describes a solution to a common problem in a context. Strategy: The real implementation of the pattern
www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I create huge objects over and over again, so project consumes so much memory. Solution: Use a single instance and reuse it whenever possible. Pattern: Singleton pattern Meaning: Create one and use it over and over. Example: Our DB connection pool
www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I have too many controllers (servlets), so I lost the control of redirecting the requests. Solution: Use a common class to redirect all requests so that you can manage in just one place. Pattern: Front controller pattern Example: DispatcherServlet in Spring framework
www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I forgot to release the resources after DB operations and I don’t want to copy and paste the same code to everywhere. Solution: Move the boilerplate code to another common class. Pattern: Template pattern Example: We will implement now.
www.javathlon.com BIG PICTURE of DESIGN PATTERNS 1. Creational Patterns a) Singleton b) Factory c) Prototype d) Builder 2. Behavioural Patterns a) Template b) Mediator 3. J2EE Patterns a) Front Controller b) DAO Pattern c) Model View Controller d) View Helper and so on...
www.javathlon.com BIG PICTURE of DESIGN PATTERNS
www.javathlon.com CORRECT USAGE DOSE of PATTERNS
www.javathlon.com IMPLEMENT TEMPLATE PATTERN Why we need them? 1- You will possibly forget common operations like closing DB connection, Prepared Statement and ResultSet. 2- You will repeatedly copy tens of lines of initialization, resource cleaning code for simple queries.
www.javathlon.com IMPLEMENT TEMPLATE PATTERN A class extends an abstract class that do the boilerplate things Concrete class Abstract class 1. Resource allocating 2. Execute DB operations Populate Result Set 3. Resource releasing Get DB Connection Create PreparedStatement Start transaction Commit transaction Close connection Close PreparedStatement Close ResultSet
www.javathlon.com DATA ACCESS OBJECT PATTERN Problem: 1- You should separate business and DB operations. In service layer, you should just deal with business. Not with DB specific ugly code, connections, etc. 2- You need a real entity object but not a collection of low level strings, numbers, booleans… 3- You need to run unit tests.
www.javathlon.com DATA ACCESS OBJECT PATTERN VIEW LAYER (Shows model’s attributes) SERVICE LAYER (Combines multiple DAOs if required) DB LAYER (DAO) Each class deal with just one DB table MODEL REAL ENTITY Get result set, place basic values into entity instances.
www.javathlon.com RELATION between DAO and TEMPLATE PATTERNS VIEW CONTROLLER DB LAYER MODEL (DAO) REAL ENTITY TEMPLATE PATTERN USED BY Get result set, place basic values into entity instances. Might be the same type of object or two separate object types that may adapted to each other
www.javathlon.com ● DAO Connection Scoping ○ Method Scope ○ Instance Scope ○ Thread Scope
www.javathlon.com UNIT TESTING DAO LAYER Unit testing means executing a method without an application server. 1- Using JUnit 2- (Fake unit testing) Simply by using an main class.
www.javathlon.com BEFORE AJAX
www.javathlon.com AFTER AJAX (Async Javascript & XML)
www.javathlon.com XMLHttpRequest object Provides the ability to 1- Send asynchronous requests to the server side. 2- Be noticed in each step of the flow (request sent, headers received, loading, done, error occurred)
www.javathlon.com XMLHttpRequest object
www.javathlon.com XXMMLLHHtttptRpeRqueeqsut eobsjte cotb mjeecthto mdsethods open(method, url) Ex: open(“POST”, “Voting”) setRequestHeader(name, value) Ex: setRequestHeader("Content-type", "application/x-www-form-urlencoded") send(data) Ex: send(“questionId=1&type=UP”)
www.javathlon.com XXMMLLHHtttptRpeRqueeqsut eobsjte c- tr meeatdhyoSdstate Shows the internal state of the XMLHttpRequest instance. When it is switched to another state, you are informed via a readyStateChangeEvent. You can update your HTML page accordingly. STATE NUMERIC VALUE DESCRIPTION UNSENT 0 The object has been constructed. OPENED 1 The open() method has been successfully invoked HEADERS_RECEIVED 2 All redirects (if any) have been followed and all HTTP headers of the final response have been received. Several response members of the object are now available. LOADING 3 The response entity body is being received. DONE 4 The data transfer has been completed or something went wrong during the transfer
www.javathlon.com Communicate with XMLHttpRequest Event name Interface Dispatched when… readystatechange Event The readyState attribute changes value, except when it changes to UNSENT. loadstart ProgressEvent The request starts. progress ProgressEvent Transmitting data. abort ProgressEvent The request has been aborted. For instance, by invoking the abort() method. error ProgressEvent The request has failed. load ProgressEvent The request has successfully completed. timeout ProgressEvent The author specified timeout has passed before the request completed. loadend ProgressEvent The request has completed (either in success or failure).
www.javathlon.com XMLHttpRequest Status codes CODE STATUS 200 SUCCESSFUL 301 MOVED PERMANENTLY 403 FORBIDDEN 404 NOT FOUND
www.javathlon.com XMLHttpRequest Handling Successful State Successful state means ● readyState = 4 ● status = 200
www.javathlon.com SUCCESSFUL AJAX FLOW HTML PAGE XMLHttpRequest instance Server Create Open Send readyStateChange:1 readyStateChange:2 process readyStateChange:3 status : 200 readyStateChange:4 status : 200 Manipulate the HTML send data to server send result (JSON, string) onReadyStateChange event
www.javathlon.com AJAX CALL FLOW ● Create an XMLHttpRequest instance. ● Configure the url and method ● Send data ● Obtain and parse the result ● Manipulate your HTML page accordingly.
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JAVA EE DEVELOPMENT (JSP and Servlets)

  • 1. JSP and SERVLET Creating Web Applications by www.javathlon.com
  • 2. www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
  • 3. www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
  • 4. www.javathlon.com HTTP PROTOCOL STANDART BEHAVIOURS ● GET method Ask server for a resource via a URI (HTML page, image, MP3 etc) ● POST method Sent a web form to server and get a resource ● Other methods HEAD, PUT, DELETE, TRACE
  • 5. www.javathlon.com Client - Server Web Applications CLIENT SERVER HTTP PROTOCOL HTML PAGE PROCESS DATA AND RESPOND WITH RESULT
  • 6. www.javathlon.com Client - Server Web Applications CLIENT HTTP PROTOCOL JSP PAGE PROCESSING UNIT (SERVLET) PROCESSING UNIT (SERVLET) SERVER PROCESSING UNIT (SERVLET) DATABASE
  • 7. www.javathlon.com NEED FOR APPLICATION SERVERS ● Dispatch requests ● Thread management ● Session management ● Caching and object pooling We will use APACHE TOMCAT
  • 8. www.javathlon.com Reminders How a J2EE project runs? ● Client side consists of JSP pages. A JSP is an HTML page with special tags to get or send dynamic data from/to server. ● Servlets carry business code on server side and redirects the client to proper pages as result. ● JSPs and servlets communicate via HTTP protocol. Mostly GET and POST methods.
  • 9. www.javathlon.com Reminders How a J2EE project runs? JSP and servlets are contained in web application servers ( servlet containers) such as Apache Tomcat. We develop configuration files such as web. xml to regulate interactions among JSPs, servlets and other resources.
  • 10. www.javathlon.com TECHNOLOGY STACK Programming IDE Servlet Container (Application server) Java Runtime Environment 6
  • 11. www.javathlon.com SERVLET MECHANISM SERVLET Http Servlet Request Return an HTML content Return a multimedia file Redirect the client to a page Forward request to another servlet Get or Post Method
  • 12. www.javathlon.com HTTPSERVLETREQUEST GET method POST method SERVLET When you enter a web address to a web browser, it requests the resource by GET method. The request body is limited to about 250 characters. Sample:https://www.google.com.tr/?q=java&safe=off&output=search You need to send a web form for using POST method. The request body is limitless
  • 13. www.javathlon.com HTTPSERVLETRESPONSE Talha Ocakci Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
  • 14. www.javathlon.com HTTPSERVLETRESPONSE Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
  • 15. www.javathlon.com SCRIPTLET in JSP A scriptlet is a piece of Java-code embedded in the HTML. The scriptlet is everything inside the <% %> tags. Between these the user can add any valid Scriplet i.e. any valid Java Code.
  • 16. www.javathlon.com IMPLICIT OBJECTS in JSP They are the objects that you can use inside scriptlets application javax.servlet.ServletContext out javax.servlet.jsp.JspWriter request javax.servlet.ServletRequest response javax.servlet.ServletResponse session javax.servlet.http.HttpSession page java.lang.Object servletconfig javax.servlet.ServletConfig
  • 17. www.javathlon.com OBJECT SCOPES in SERVLETCONTEXT Application Scope Request Scope Session scope
  • 18. www.javathlon.com HTTP SESSION OBJECT SESSION ID Session object Attribute map name1 value1 name2 value2
  • 19. www.javathlon.com HTTPSERVLETRESPONSE Talha Ocakci Return an HTML content Return a multimedia file Navigate the client to another page Forward request to another servlet SERVLET Request Content-Type: text/html Use: PrintWriter object of HTTPServletResponse Content-Type: application/pdf, image/jpeg... Use: OutputStream object of HTTPServletResponse Content-Type: none Use: sendRedirect() method Content-Type: none Use: RequestDispatcher object of ServletContext
  • 20. www.javathlon.com REDIRECTING REQUEST Request forwarding and redirection are different concepts. When you forward a request, request and response objects are transferred. Url stays the same. When you redirect the request to another JSP/servlet, request and response objects are not transferred to new object. URL changes to the directory of new page.
  • 21. www.javathlon.com Tip for being a wanted J2EE developer ● Avoid using JAVA code inside a JSP file. Use JSP directives and JSP actions instead. ● Avoid using HTML code inside a servlet. Instead, use HTML code in JSP page and pass values it from the servlet.
  • 22. www.javathlon.com JSP Actions ● jsp:useBean Searches for an objects inside the given scope ● jsp:getProperty ● jsp:setProperty Gets/sets a value of a given object
  • 23. www.javathlon.com jsp:useBean action <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInfo" scope="request"> </jsp:useBean> request.getParameter(“memberInfo”) <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInfo scope="session"> </jsp:useBean> request.getSession().getParameter(“memberInfo”) <jsp:useBean id="memberInfo" class="com.qapro.register.MemberInf scope="application"> </jsp:useBean> ServletContext sc = getServletContext(); sc.getAttribute(“memberInfo”)
  • 24. www.javathlon.com jsp:getProperty and jsp:setProperty Gets/sets an attribute of an object with a given id
  • 25. www.javathlon.com JSTL BASICS Java Server Tag Library Provides shorthand notation to access: ● Attributes of standard servlet objects ● Bean properties We use them, because writing JAVA code inside JSP is not a good practice. It is a third party library of Apache Foundation.
  • 26. www.javathlon.com JSTL and JAVA Code Relation Iterating over a list JAVA NOTATION <ul> <% for(int i=0; i<messages.length; i++) { String message = messages[i]; %> <li><%= message %></li> <% } %> </ul> JSTL NOTATION <ul> <c:forEach var="message” items="${messages}"> <li>${message}</li> </c:forEach> </li>
  • 28. www.javathlon.com CLUE WEB APPLICATION WEB BROWSER ask for sth show result
  • 29. www.javathlon.com CLUE A basic web application is nothing more than a system that populates data from a database, insert into it, modify the data and visualize it. USER INTERFACE DATABASE WEB APPLICATION sends input select delete & update insert shows result
  • 30. www.javathlon.com WORKING WITH DATABASE Description A database is any file or file system that you can ● store your data ● manipulate data ● search for a desired item
  • 31. www.javathlon.com WORKING WITH DATABASE Database Types ● Flat files (text or binary) ● Flat file systems ● Non - relational databases (eg. MongoDB) ● Relational databases (eg. MySQL)
  • 32. www.javathlon.com WORKING WITH DATABASE Why use RDBMS? Relational Database Systems: Ease your tasks for quickly inserting, updating, querying, deleting the data you have on your hands using SQL.
  • 33. www.javathlon.com WORKING WITH DATABASE Relational Databases Relational Database Systems: Stores the data in tables and relations between those tables.
  • 34. www.javathlon.com WORKING WITH DATABASE Relational Database Structure Table: A real world or imaginary entity model that has attributes. (A user metadata) Row: An instance of a entity model (A user instance) Column: Attribute of an entity (User’s name) Primary key: Identifier of a instance (User’s id) Foreign key: Dependency of an entity to another entity (Reference to user’s question)
  • 35. WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Tables and columns Keep track of all money transfers in a bank. You need to store this data permanently. ROW 1 ROW 2 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Date 1.1.2014 Sender name Kirk Sender surname Hammett Sender account no 565656565 Receiver name James Receiver surname Hetfield Receiver account no 808080801 Amount 50000 Currency USD Date 3.1.2014 attribute value DB TABLE (MONEY TRANSFER)
  • 36. www.javathlon.com SQL (Structured Query Language) ● DDL (Data Definition Language) Used to create or modify tables, data types of columns ● DML (Data Manipulation Language) Used to insert, update, delete data and query for desired data
  • 37. www.javathlon.com DATA TYPES ● String types ● Numeric types ● Date & Time types ● Binary objects
  • 38. www.javathlon.com WORKING WITH RELATIONAL DATABASES Creating table structures Done with DDL (Data Definition Language ) CREATE TABLE money_transfer( transfer_id INTEGER PRIMARY KEY, sender_name VARCHAR(50) NULL, sender_surname VARCHAR(50) NULL, sender_surname VARCHAR(50) NULL, sender_account_no VARCHAR(20) NULL, receiver_name VARCHAR(50) NULL, receiver_surname VARCHAR(50) NULL, receiver_account_no VARCHAR(50) NULL, amount FLOAT; currenct VARCHAR(4) NULL, transfer_date DATE NULL ); Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Transfer Date 1.1.2014
  • 39. WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Breaking the data into smaller units Multiple similar records means lots of repetition and repetition means mess. For preventing the repetition, we break the data into multiple columns. Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Paul Receiver surname McCartney Receiver account no 12121212121 Amount 300 Currency USD Date 1.1.2014 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name George Receiver surname Harrison Receiver account no 12045872 Amount 400 Currency USD Date 1.2.2014 Sender name John Sender surname Lennon Sender account no 79879878978 Receiver name Ringo Receiver surname Start Receiver account no 13698985 Amount 500 Currency USD Date 1.3.2014
  • 40. WORKING WITH RELATIONAL www.javathlon.com DATABASES First example - Data normalization ● Basic client data is extracted from the money transfer information. ● Client data is stored in another table. Identifier of the record inside client table is referenced from money transfer table Sender Client data 121 Receiver name George Receiver surname Harrison Receiver account no 12045872 Amount 400 Currency USD Date 1.2.2014 Sender Client data 121 Receiver name Ringo Receiver surname Starr Receiver account no 13698985 Amount 500 Currency USD Date 1.3.2014 Client data Client id 121 Client name John Client surname Lennon Client account no 79879878978 Client id( Foreign key)
  • 41. www.javathlon.com Tip for being a wanted J2EE developer A database table SHOULD correspond to at least one real world or virtual entity. DATABASE TABLE DESIGN PRINCIPLES 1
  • 42. www.javathlon.com Tip for being a wanted J2EE developer 2 Dependent entities should reference to the owner entity for data integration. DATABASE TABLE DESIGN PRINCIPLES
  • 43. www.javathlon.com DATABASE DESIGN for the USER MANAGEMENT MODULE of QA PLATFORM
  • 44. www.javathlon.com REGISTRATION Insert a user with ● username, ● password ● and other personal details.
  • 45. www.javathlon.com AUTHENTICATION Check if given username-password pair exists in database.
  • 46. www.javathlon.com REGISTRATION DB SCHEMA STANDART MUST-DOs 1. Put a primary key. 2. Put insertion date, 3. Put active/passive bit BUSINESS SPECIFIC 1. Store username and password 2. Store personal details
  • 47. www.javathlon.com REGISTRATION CREATE TABLE CREATE TABLE `user` ( `user_id` int(11) NOT NULL, `user_name` varchar(45) DEFAULT NULL, `password` varchar(45) COLLATE DEFAULT NULL, `is_active` bit(1) DEFAULT NULL, `name` varchar(45) DEFAULT NULL, `surname` varchar(45) DEFAULT NULL, `insert_date` datetime DEFAULT NULL, `role_name` varchar(45) DEFAULT NULL, PRIMARY KEY (`user_id`) )
  • 48. A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com with SQL Insert data INSERT INTO TABLENAME (first_column,...last_column) VALUES (first_value,...last_value); INSERT INTO user (user_id, user_name, password) VALUES (1, 'paul_weller','hzf1234fddf')
  • 49. A PRIMER FOR DATA MANIPULATwwIwO.javNath lon.com with SQL Primary key insert into user (user_id, user_name, password) values(100, 'paul_weller','hzf1234fddf') Error Code: 1062. Duplicate entry '100' for key 'PRIMARY' 0.000 sec Each table HAS TO have a primary key. This lets your database vendor to allocate unique space for each record in any tables. insert into user ( user_name, password) values ('eddie_vedder','hzf1234fddf'); Each table HAS TO have a primary key. This lets your database vendor to allocate unique space for each record in any tables. You will see user_id column gets unique values one by one.
  • 50. www.javathlon.com A PRIMER FOR DATA MANIPULATION with SQL Update a record update TABLENAME set COLUMNNAME = VALUE update user set user_name= ‘hgklkg45784’
  • 51. www.javathlon.com A PRIMER FOR DATA RETRIEVAL with SQL Retrieve all records DO NOT use * in select clauses. Using * is a good example of cutting corners that junior developers do. Define which columns you exactly need and want to populate.
  • 52. A PRIMER FOR DATA RETRIEVAL wwwwi.jtavhath lon.com SQL Restrict records select COLUMN1,COLUMN2 from TABLENAME where COLUMN1 = VALUE and/or COLUMN2 = VALUE2 select user_name from user where user_name =’'paul_weller'’ and password = ‘'hzf1234fddf'’
  • 53. www.javathlon.com IN NEXT CHAPTER ● Database Connections ● Transactions ● What is ACID? ● Committing and rolling the transactions back ● DB Engine - Java communication
  • 54. www.javathlon.com DATABASE CONNECTIONS Database connection is the means by which a database server and its client software communicate with each other.
  • 55. www.javathlon.com WHY WE NEED DATABASE CONNECTIONS? We send the commands to DB server and get the results via an open DB connection. DB SERVER Java web application DB CONNECTION
  • 56. www.javathlon.com COMMUNICATION BETWEEN JAVA AND DATABASE Database talks SQL, but Java does not know how to talk in SQL, it needs a translator called JDBC (Java Database Connector).
  • 57. www.javathlon.com DB CONNECTION POOLS DB connection opening and closing is so expensive operations compared to execute basic queries. Instead of open/close a connection for each query, create a bunch of connections* and use them over and over again. * = Connection pool
  • 59. www.javathlon.com CONNECTION POOL Implementations in Java ● C3P0 ● BoneCP ...
  • 60. www.javathlon.com DATABASE TRANSACTIONS A unit of work performed within a database management system against a database.
  • 61. www.javathlon.com DATABASE TRANSACTIONS ALL OR NOTHING PRINCIPLE 1. Open connection 2. Begin transaction 3. Debit $100 to Groceries Expense Account 4. Credit $100 to Checking Account 5. Commit transaction 6. Close connection TRANSACTION
  • 62. www.javathlon.com ACID Properties that a transaction must have Atomicity: Based on “all or nothing” principle All statements succeed or all fail in case of any power failures, errors, and crashes.
  • 63. www.javathlon.com ACID Properties that a transaction must have Consistency: If, for some reason (eq: programming error), a transaction is executed that violates the database’s consistency rules, the entire transaction will be rolled back and the database will be restored to a state consistent with those rules. eq: NULL inserting to a not-nullable column
  • 64. www.javathlon.com ACID Properties that a transaction must have Isolation: Before committing a transaction, modifications should not be visible to another transaction.
  • 65. www.javathlon.com ACID Properties that a transaction must have Durability: Durability guarantees that the database will keep track of pending changes in such a way that the server can recover from an abnormal termination.
  • 66. www.javathlon.com DATABASE DESIGN for the USER ROLE MANAGEMENT MODULE
  • 67. www.javathlon.com User Role- Permissions Logic MODERATOR MODIFY POST DELETE POST CREATE POST USER 1 USER 2
  • 68. www.javathlon.com User Role- Permissions Logic Required permissions: 1- Deleting posts 2- Correcting posts Required permissions: 1- Accepting new users 2- Deleting users John Hopkins is a moderator. A moderator has permissions for 1- Deleting posts 2- Correcting posts
  • 69. www.javathlon.com Tip for being a wanted J2EE developer Why not assign the permissions directly to the user but assign to a role? Because adding or removing the permissions to a role, lets the system grant or revoke this permission from all the users who belong to this role. Otherwise you would execute this modification on all users and this means a huge cost.
  • 70. www.javathlon.com Requirements: ● TABLE RELATIONS (1 to MANY, MANY to 1, MANY to MANY) ● SQL JOINS (inner join, left join, right join, full join, self join)
  • 71. www.javathlon.com THE MEANING OF RELATIONAL in RELATIONAL DATABASES One object may belong to how many other owner objects? One object may own to how many other dependent objects?
  • 72. www.javathlon.com TABLE RELATIONS ONE TO ONE USER USER-DETAILS (Country, Height, Weight ...) If you safely can add the columns in one table to another relation means 1-1.
  • 73. www.javathlon.com TABLE RELATIONS ONE TO ONE OPTION 1 USER TABLE USER ID USER NAME COUNTRY REGISTRATION DATE HEIGHT WEIGHT TIMEZONE USER TABLE USER ID USER NAME REGISTRATION DATE USER DETAILS TABLE USER ID HEIGHT WEIGHT COUNTRY OPTION 2
  • 74. www.javathlon.com TABLE RELATIONS ONE TO MANY ONE MANY QUESTION ANSWER 1 ● A question may own two answers. ● But, an answer can not be given two multiple questions. ANSWER 2 QUESTION ANSWER 3
  • 75. www.javathlon.com TABLE RELATIONS MANY TO MANY MANY MANY USER TOPIC 1 ● A user may follow multiple topics ● A topic may be followed by multiple users. TOPIC 2 USER TOPIC 3
  • 76. www.javathlon.com TABLE RELATIONS MANY TO MANY USER TABLE USER ID USER NAME USER NICKNAME 1 Talha Ocakçı talhaocakci 2 James Dio dio TOPIC TABLE TOPIC ID TOPIC NAME 1 Geography 2 History USER FOLLOWED TOPICS USER ID TOPIC ID FOLLOW TIME 1 1 10.06.2014 2 1 18.06.2014 2 2 18.07.2014
  • 77. www.javathlon.com JOINING TABLES To retrieve and combine different attributes of an entity from several tables. SELECT CLAUSE + FROM CLAUSE + JOIN CLAUSE (multiple) + WHERE CLAUSE +
  • 78. www.javathlon.com JOINING TABLES Inner Join Both tables must have the same value on joined columns. eq. Populate list of permissions that a user has.
  • 79. www.javathlon.com JOINING TABLES Left (Outer) Join If a row in table 1 does not have a match in table 2, it still exists in result set.
  • 81. IMPLEMENTING JAVA WEB APPLICATION
  • 82. www.javathlon.com WHAT WE WILL DO? 1. Without caring of user interface design, focus on the technical details. 2. Find the most time consuming phases in development and ease them professionally
  • 83. www.javathlon.com REGISTER USER Get username, email, name, surname of user and post it to servlet JSP 1. Get values from request 2. Get DB connection (Create or get one from DB connection pool) 3. Start transaction 4. Insert user to DB 5. Release all resources 6. Put message into response 6. Redirect to another page SERVLET Show the message inside JSP
  • 84. www.javathlon.com JDBC CLASSES Statement ● Contains a static SQL statement ● Not reusable PreparedStatement: ● Contains precompiled SQL statement. ● Used to efficiently execute this statement multiple times by just setting parameters.
  • 85. www.javathlon.com JDBC CLASSES ResultSet Holds the database result row by row Holds the metadata of the DB result (count, column names, etc)
  • 86. www.javathlon.com JAVA - MYSQL TYPE CORRESPONDENCE
  • 87. www.javathlon.com RESULT SET OBJECT VALUES METADATA talha ocakci talhaocakci paul auster paulauster ... ... ... Count Column types Schema name Table name ... POINTER
  • 88. www.javathlon.com RESULT SET OBJECT resultset.next() method moves the pointer to next row. If reaches to the end it returns false. talha ocakci talhaocakci paul auster paulauster ... ... ... POINTER Initially, it points to the very beginning of the ResultSet object but not the first row. To get the first row, you need to invoke next() before iterating.
  • 89. www.javathlon.com REGISTER USER Get username, email, name, surname of user and post it to servlet JSP 1. Get values from request 2. Get DB connection (Create or get one from DB connection pool) 3. Start transaction 4. Insert user to DB 5. Release all resources 6. Put message into response 6. Redirect to another page SERVLET Show the message inside JSP
  • 90. www.javathlon.com CONNECTION POOLS Created on servlet containers (Tomcat 7) or application servers (JBOSS, Glassfish, etc..) and can be access by JNDI Created with C3P0 independent from a servlet container or an application server.
  • 91. www.javathlon.com CONNECTION POOLS Configuration Min connection size: Whatever happens, connection number will not drop below this. Max connection: Number of connection can not exceed this number. Timeout: If idle time of a connection exceeds this time, it returns back to pool automatically.
  • 92. www.javathlon.com INITIALIZE RESOURCE WHILE BOOTSTRAPPING ● Mark your servlet for automatic invoking while bootstrapping the application in deployment descriptor. marker: load-on-startup tag. ● Initialize resources in init() method of servlet.
  • 93. www.javathlon.com EMAIL VALIDATION 1- Insert the new user record to user table 2- Insert a related record to email-validation table including user id and validation code. 3- Email the validation url including the validation code to user’s email. 4- When sent link is clicked, check the validation code in url against the one in DB.
  • 94. www.javathlon.com EMAIL VALIDATION When a connection is created, it is in auto-commit mode. The way to allow two or more statements to be grouped into a transaction is to disable the auto-commit mode.
  • 95. www.javathlon.com GET GENERATED KEYS preparedStatement.getGeneratedKeys() returns a Result Set with one column and one row: POINTER VALUES 29
  • 96. www.javathlon.com WORKING IN PROFESSIONAL SOFTWARE DEVELOPMENT TEAMS
  • 97. www.javathlon.com WORKING IN A TEAM If team members use; ● Different approaches to similar problems ● Different relations between software layers... There will be chaos later on.
  • 98. www.javathlon.com WORKING IN PROFESSIONAL SOFTWARE DEVELOPMENT TEAMS Why do we use design patterns? Developers agree on the best solutions and apply them for similar problems.
  • 99. www.javathlon.com SOFTWARE ARCHITECTURE AND DESIGN PATTERNS Design patterns ensure the project will not fail by the time passing. If you don’t obey the rules, the failure underneath will be observed.
  • 100. www.javathlon.com DESIGN PATTERN and STRATEGY Design Pattern: Describes a solution to a common problem in a context. Strategy: The real implementation of the pattern
  • 101. www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I create huge objects over and over again, so project consumes so much memory. Solution: Use a single instance and reuse it whenever possible. Pattern: Singleton pattern Meaning: Create one and use it over and over. Example: Our DB connection pool
  • 102. www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I have too many controllers (servlets), so I lost the control of redirecting the requests. Solution: Use a common class to redirect all requests so that you can manage in just one place. Pattern: Front controller pattern Example: DispatcherServlet in Spring framework
  • 103. www.javathlon.com EXAMPLES in SOFTWARE ENGINEERING Problem: I forgot to release the resources after DB operations and I don’t want to copy and paste the same code to everywhere. Solution: Move the boilerplate code to another common class. Pattern: Template pattern Example: We will implement now.
  • 104. www.javathlon.com BIG PICTURE of DESIGN PATTERNS 1. Creational Patterns a) Singleton b) Factory c) Prototype d) Builder 2. Behavioural Patterns a) Template b) Mediator 3. J2EE Patterns a) Front Controller b) DAO Pattern c) Model View Controller d) View Helper and so on...
  • 105. www.javathlon.com BIG PICTURE of DESIGN PATTERNS
  • 106. www.javathlon.com CORRECT USAGE DOSE of PATTERNS
  • 107. www.javathlon.com IMPLEMENT TEMPLATE PATTERN Why we need them? 1- You will possibly forget common operations like closing DB connection, Prepared Statement and ResultSet. 2- You will repeatedly copy tens of lines of initialization, resource cleaning code for simple queries.
  • 108. www.javathlon.com IMPLEMENT TEMPLATE PATTERN A class extends an abstract class that do the boilerplate things Concrete class Abstract class 1. Resource allocating 2. Execute DB operations Populate Result Set 3. Resource releasing Get DB Connection Create PreparedStatement Start transaction Commit transaction Close connection Close PreparedStatement Close ResultSet
  • 109. www.javathlon.com DATA ACCESS OBJECT PATTERN Problem: 1- You should separate business and DB operations. In service layer, you should just deal with business. Not with DB specific ugly code, connections, etc. 2- You need a real entity object but not a collection of low level strings, numbers, booleans… 3- You need to run unit tests.
  • 110. www.javathlon.com DATA ACCESS OBJECT PATTERN VIEW LAYER (Shows model’s attributes) SERVICE LAYER (Combines multiple DAOs if required) DB LAYER (DAO) Each class deal with just one DB table MODEL REAL ENTITY Get result set, place basic values into entity instances.
  • 111. www.javathlon.com RELATION between DAO and TEMPLATE PATTERNS VIEW CONTROLLER DB LAYER MODEL (DAO) REAL ENTITY TEMPLATE PATTERN USED BY Get result set, place basic values into entity instances. Might be the same type of object or two separate object types that may adapted to each other
  • 112. www.javathlon.com ● DAO Connection Scoping ○ Method Scope ○ Instance Scope ○ Thread Scope
  • 113. www.javathlon.com UNIT TESTING DAO LAYER Unit testing means executing a method without an application server. 1- Using JUnit 2- (Fake unit testing) Simply by using an main class.
  • 115. www.javathlon.com AFTER AJAX (Async Javascript & XML)
  • 116. www.javathlon.com XMLHttpRequest object Provides the ability to 1- Send asynchronous requests to the server side. 2- Be noticed in each step of the flow (request sent, headers received, loading, done, error occurred)
  • 118. www.javathlon.com XXMMLLHHtttptRpeRqueeqsut eobsjte cotb mjeecthto mdsethods open(method, url) Ex: open(“POST”, “Voting”) setRequestHeader(name, value) Ex: setRequestHeader("Content-type", "application/x-www-form-urlencoded") send(data) Ex: send(“questionId=1&type=UP”)
  • 119. www.javathlon.com XXMMLLHHtttptRpeRqueeqsut eobsjte c- tr meeatdhyoSdstate Shows the internal state of the XMLHttpRequest instance. When it is switched to another state, you are informed via a readyStateChangeEvent. You can update your HTML page accordingly. STATE NUMERIC VALUE DESCRIPTION UNSENT 0 The object has been constructed. OPENED 1 The open() method has been successfully invoked HEADERS_RECEIVED 2 All redirects (if any) have been followed and all HTTP headers of the final response have been received. Several response members of the object are now available. LOADING 3 The response entity body is being received. DONE 4 The data transfer has been completed or something went wrong during the transfer
  • 120. www.javathlon.com Communicate with XMLHttpRequest Event name Interface Dispatched when… readystatechange Event The readyState attribute changes value, except when it changes to UNSENT. loadstart ProgressEvent The request starts. progress ProgressEvent Transmitting data. abort ProgressEvent The request has been aborted. For instance, by invoking the abort() method. error ProgressEvent The request has failed. load ProgressEvent The request has successfully completed. timeout ProgressEvent The author specified timeout has passed before the request completed. loadend ProgressEvent The request has completed (either in success or failure).
  • 121. www.javathlon.com XMLHttpRequest Status codes CODE STATUS 200 SUCCESSFUL 301 MOVED PERMANENTLY 403 FORBIDDEN 404 NOT FOUND
  • 122. www.javathlon.com XMLHttpRequest Handling Successful State Successful state means ● readyState = 4 ● status = 200
  • 123. www.javathlon.com SUCCESSFUL AJAX FLOW HTML PAGE XMLHttpRequest instance Server Create Open Send readyStateChange:1 readyStateChange:2 process readyStateChange:3 status : 200 readyStateChange:4 status : 200 Manipulate the HTML send data to server send result (JSON, string) onReadyStateChange event
  • 124. www.javathlon.com AJAX CALL FLOW ● Create an XMLHttpRequest instance. ● Configure the url and method ● Send data ● Obtain and parse the result ● Manipulate your HTML page accordingly.