Struts2 - 101
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Struts 2 is an open source MVC framework based on Java EE standards. It uses a request-response pipeline where interceptors pre-process and post-process requests. The core components are interceptors, actions, and results. Interceptors provide functionality like validation while actions contain application logic and results define the response. Values are stored and accessed from a value stack using OGNL.
![ValueStack
The Action instance is always pushed onto the value stack and since the stack is the
OGNL root, references to Action properties can omit the # marker.
<s:property value=“customer.address"/>
But, to access other objects in the ActionContext, we must use the # notation so
OGNL knows not to look in the root object, but for some other object in the
ActionContext.
<s:property value="#session.mySessionPropKey"/> or
<s:property value="#session['mySessionPropKey']"/> or
<s:property value="#request['myRequestPropKey']"/>
The ActionContext is also exposed to Action classes via a static method.
ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject);
40](https://image.slidesharecdn.com/struts2-120728081800-phpapp02/85/Struts2-101-40-320.jpg)
![ValueStack
The Action instance is always pushed onto the value stack and since the stack is the
OGNL root, references to Action properties can omit the # marker.
<s:property value=“customer.address"/>
But, to access other objects in the ActionContext, we must use the # notation so
OGNL knows not to look in the root object, but for some other object in the
ActionContext.
<s:property value="#session.mySessionPropKey"/> or
<s:property value="#session['mySessionPropKey']"/> or
<s:property value="#request['myRequestPropKey']"/>
The ActionContext is also exposed to Action classes via a static method.
ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject);
41](https://image.slidesharecdn.com/struts2-120728081800-phpapp02/85/Struts2-101-41-320.jpg)
![ValueStack
The Action instance is always pushed onto the value stack and since the stack is the
OGNL root, references to Action properties can omit the # marker.
<s:property value=“customer.address"/>
But, to access other objects in the ActionContext, we must use the # notation so
OGNL knows not to look in the root object, but for some other object in the
ActionContext.
<s:property value="#session.mySessionPropKey"/> or
<s:property value="#session['mySessionPropKey']"/> or
<s:property value="#request['myRequestPropKey']"/>
The ActionContext is also exposed to Action classes via a static method.
ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject);
42](https://image.slidesharecdn.com/struts2-120728081800-phpapp02/85/Struts2-101-42-320.jpg)
Struts2 - 101
- 1. Struts 2 1
- 2. Agenda What is Struts ? Features How Struts works? Request – Response Pipeline Different components of Struts Difference between Struts 1 and Struts 2 Creating your first Struts 2 Application 2
- 3. Background of Struts 2 Not Struts 1.x! EE5 Web Framework Originally OpenSymphony WebWork WebWork + Struts + Apache Incubator Struts 2 was hatched in „07 3
- 4. What is Struts? Feature of Struts 4
- 5. What exactly is Struts 2? An MVC Framework 5
- 6. What exactly is Struts 2? An MVC Framework Is Open Source Based on Java EE Servlet API 2.4 JSP API 2.0 Java 5 6
- 7. Features • Simple Architecture 7
- 8. Features • Simple Architecture • Spring as default inversion of control container 8
- 9. Features • Simple Architecture • Spring as default inversion of control container • Page-based Navigation 9
- 10. Features • Simple Architecture • Spring as default inversion of control container • Page-based Navigation • Built-in Ajax Support: DWR and Dojo 10
- 11. Features • Simple Architecture • Spring as default inversion of control container • Page-based Navigation • Built-in Ajax Support: DWR and Dojo • Much better client-side validation support 11
- 12. Features • Simple Architecture • Spring as default inversion of control container • Page-based Navigation • Built-in Ajax Support: DWR and Dojo • Much better client-side validation support • JSF Support 12
- 13. Features • Simple Architecture • Spring as default inversion of control container • Page-based Navigation • Built-in Ajax Support: DWR and Dojo • Much better client-side validation support • JSF Support • Built-in support for testing with StrutsTestCase 13
- 14. How Struts works? Request – Response Pipeline 14
- 15. Working of Struts 2 Framework Core components of the framework Interceptors Actions Results Filter Dispatcher (Controller) 15
- 16. Request – Response Pipeline 16
- 17. Request – Response Pipeline – Step 1 17
- 18. Request – Response Pipeline – Step 2 18
- 19. Request – Response Pipeline – Step 3 19
- 20. Request – Response Pipeline – Step 4 20
- 21. Request – Response Pipeline – Step 5 21
- 22. Request – Response Pipeline – Step 6 22
- 23. Request – Response Pipeline – Step 7 23
- 24. Different Components of Struts Core Component – Interceptor, Action & Result Other concept – ValueStack, OGNL, Configuration Files,Validations 24
- 25. Interceptors They provide a way to supply pre-processing and post-processing around the action. examples include double-submit guards, type conversion, object population, validation, file upload, page preparation, exception handling Not thread safe <interceptors> <interceptor name="autowiring“ class="interceptor.ActionAutowiringInterceptor"/> </interceptors> <action name="my" class="com.test.MyAction" > <result>view.jsp</result> <interceptor-ref name="autowiring"/> </action> 25
- 26. Interceptor Stack An interceptor has a specific role Parameter interception Validation Workflow Named “stacks” provide pluggable lists pre-assembled for goal specific cases defaultStack fileUploadStack modelDrivenStack paramsPrepareParamsStack 26
- 27. Common Interceptors Interceptor Description Checkbox Interceptor Adds automatic checkbox handling code that detect an unchecked checkbox and add it as a parameter with a default (usually 'false') value. Create Session Create an HttpSession automatically, useful with certain Interceptor Interceptors that require a HttpSession to work properly (like the TokenInterceptor) File upload Interceptor An Interceptor that adds easy access to file upload support. I18n Interceptor Remembers the locale selected for a user's session. Logger Interceptor Outputs the name of the Action. ExecuteAndWait Executes the Action in the background and then sends the user off Interceptor to an intermediate waiting page. 27
- 28. Common Interceptors Cont’d Interceptor Description Scope Interceptor Simple mechanism for storing Action state in the session or application scope. Parameters Interceptor Sets the request parameters onto the Action. Roles Interceptor Action will only be executed if the user has the correct JAAS role. Profiling Interceptor Activate profiling through parameter Validation Interceptor Performs validation using the validators defined in action- validation.xml Exception Interceptor Maps exceptions to a result. Cookie Interceptor Inject cookie with a certain configurable name / value into action. 28
- 29. Timer Interceptor Stopwatch feature for action execution “starts” before your action “stops” afterward Writes performance timings to log <interceptors> <interceptors> <interceptor-stack name="stackWithTimer"> <interceptor-stack name="stackWithTimer"> <interceptor-ref name="timer"/> <interceptor-ref name="defaultStack"/> <interceptor-ref name="defaultStack"/> <interceptor-ref name="timer"/> </interceptor-stack> </interceptor-stack> </interceptors> </interceptors> records action's execution with interceptors records only the action's execution time 29
- 30. Default Stack <interceptor-stack name="defaultStack"> <interceptor-ref name="exception"/> <interceptor-ref name="alias"/> <interceptor-ref name="servletConfig"/> <interceptor-ref name="prepare"/> <interceptor-ref name="i18n"/> <interceptor-ref name="chain"/> <interceptor-ref name="debugging"/> <interceptor-ref name="profiling"/> <interceptor-ref name="scopedModelDriven"/> <interceptor-ref name="modelDriven"/> <interceptor-ref name="fileUpload"/> <interceptor-ref name="checkbox"/> <interceptor-ref name="staticParams"/> <interceptor-ref name="params"> <param name="excludeParams">dojo..*</param> </interceptor-ref> <interceptor-ref name="conversionError"/> <interceptor-ref name="validation"> <param name="excludeMethods">input,back,cancel,browse</param> </interceptor-ref> <interceptor-ref name="workflow"> <param name="excludeMethods">input,back,cancel,browse</param> </interceptor-ref> </interceptor-stack> 30
- 31. Actions Extend ActionSupport ThreadLocal (safe) Contain your domain model or can be model driven May contain multiple methods Easy to test! 31
- 32. Action Mapping <package name=“test" namespace="/test" extends="starter"> <action name=“uri“ class=“class“ method=“method"> <result>destination</result> </action> <package> 32
- 33. Result What should be returned to requester? Many provided out of the box It‟s easy to write your own Graphics JSON PDF It‟s another configurable object 33
- 34. Result Types Result Type Description Chain Result Used for Action Chaining Used for web resource integration, Dispatcher Result including JSP integration FreeMarker Result Used for FreeMarker integration HttpHeader Result Used to control special HTTP behaviors Redirect Result Used to redirect to another URL (web resource) 34
- 35. Result Types Cont’d Result Type Description Redirect Action Result Used to redirect to another action mapping Used to stream an InputStream back to the browser Stream Result (usually for file downloads) Velocity Result Used for Velocity integration Used to display the raw content of a particular page PlainText Result (i.e jsp, HTML) Tiles Result Used to provide Tiles integration 35
- 36. Result Example <action …> <result name="success" type="dispatcher"> /employee/list.jsp </result> </action> name and type are optional name defaults to success type default can be set by package 36
- 37. ValueStack & OGNL A ValueStack is a place where all the data related to action and the action itself is stored OGNL is a mean through which the data in the ValueStack is manipulated. 37
- 38. ValueStack • Leverages the OGNL framework Object Graph Navigation Language • Extends OGNL to support searching stack Top down to locate object/property • Where Interceptors put/get object data • Thread Safe • ActionContext.getContext().getValueStack() Map<String, Object> context = new HashMap<String, Object>(); context.put("key", "some object"); context.put("key2", "another object"); ActionContext.getContext().getValueStack().push(context); 38
- 39. Struts 2 and OGNL 39
- 40. ValueStack The Action instance is always pushed onto the value stack and since the stack is the OGNL root, references to Action properties can omit the # marker. <s:property value=“customer.address"/> But, to access other objects in the ActionContext, we must use the # notation so OGNL knows not to look in the root object, but for some other object in the ActionContext. <s:property value="#session.mySessionPropKey"/> or <s:property value="#session['mySessionPropKey']"/> or <s:property value="#request['myRequestPropKey']"/> The ActionContext is also exposed to Action classes via a static method. ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject); 40
- 41. ValueStack The Action instance is always pushed onto the value stack and since the stack is the OGNL root, references to Action properties can omit the # marker. <s:property value=“customer.address"/> But, to access other objects in the ActionContext, we must use the # notation so OGNL knows not to look in the root object, but for some other object in the ActionContext. <s:property value="#session.mySessionPropKey"/> or <s:property value="#session['mySessionPropKey']"/> or <s:property value="#request['myRequestPropKey']"/> The ActionContext is also exposed to Action classes via a static method. ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject); 41
- 42. ValueStack The Action instance is always pushed onto the value stack and since the stack is the OGNL root, references to Action properties can omit the # marker. <s:property value=“customer.address"/> But, to access other objects in the ActionContext, we must use the # notation so OGNL knows not to look in the root object, but for some other object in the ActionContext. <s:property value="#session.mySessionPropKey"/> or <s:property value="#session['mySessionPropKey']"/> or <s:property value="#request['myRequestPropKey']"/> The ActionContext is also exposed to Action classes via a static method. ActionContext.getContext().getSession().put("mySessionPropKey", mySessionObject); 42
- 43. Type Conversions OGNL uses reflection to convert types JavaBeans convention provides “hint” Custom converters can be added Scope Bean/Model Action Application 43
- 44. Configuration Files File Optional Location Purpose Web.xml No /WEB_INF/ Web deployment descriptor to include all necessary framework components Struts.xml Yes /WEB_INF/classes Main configuration, contains result/view types, action mappings, interceptors, and so forth Struts.prop Yes /WEB_INF/classes Framework properties erties Strusts.defa Yes /WEB-INF/lib/ Default configuration provided by ult.xml struts2-core.jar Struts 44
- 45. struts.xml Core configuration file for framework Can contain multiple packages <struts> <package name=“base“ extends="struts-default"> <result-types>…</result-types> <interceptors><interceptor-stack name="starterStack"> <interceptor-ref name="timer" /> <interceptor-ref name="scopedModelDriven" /> <interceptor-ref name="paramsPrepareParamsStack" /> </interceptor-stack> </interceptors> <default-interceptor-ref name="starterStack" /> </package> <include file=“base.xml" /> <include file=“preferences.xml" /> </struts> 45
- 47. struts-default.xml Most of your packages will extend this Directly/Indirectly Contains about everything you need Packages form inheritance hierarchies The key sections are <package name=“base“ extends="struts-default"> package <result-types>…</result-types> result-types <interceptors><interceptor-stack name="starterStack"> interceptors/stacks <interceptor-ref name="timer" /> <interceptor-ref name="scopedModelDriven" /> <interceptor-ref name="paramsPrepareParamsStack" /> </interceptor-stack> </interceptors> <default-interceptor-ref name="starterStack" /> </package> 47
- 48. Constant Configuration Modify framework and plug-in behavior Can be declared at multiple levels Searched in the following order struts-default.xml struts-plugin.xml struts.xml struts.properties web.xml Subsequent files override previous ones 48
- 49. Validations Validation Styles Annotations XML Java Dependent on Validation Interceptor Workflow Interceptor 49
- 50. Simple Field Example Form <s:textfield key="age"/> Action private int age; get/set Validator <ActionClassName>-validation.xml <field name="age"> <field-validator type="int"> <param name="min">13</param> <param name="max">19</param> <message>must be between ${min} and ${max}, current value is ${bar}</message> </field-validator> </field> 50
- 51. Validator Types conversion date email short – int – long - double regex <takes a regular expression> required requiredstring stringlength url visitor - conditionalvisitor fieldexpression <resolves an OGNL expression> expression <resolves an OGNL expression> 51
- 52. Non-Field vs Field Validation <validators> <validator type="expression"> <param name="expression“> ( (a==b) && (b==c) )</param> <message>all three fields must be the same></message> </validator> </validators> <field name="email_address"> <field-validator type="required"> <message>You cannot leave the email address field empty.</message> </field-validator> <field-validator type="email"> <message>The email address you entered is not valid.</message> </field- validator> </field> 52
- 53. Difference between Struts 1 and Struts 2 53
- 54. Action Classes Struts 1 Struts 2 Struts 1 requires Action classes to An Struts 2 Action may implement extend an abstract base class. A an Action interface, along with other common problem in Struts 1 is interfaces to enable optional and programming to abstract classes custom services. Struts 2 provides a instead of interfaces. base ActionSupport class to implement commonly used interfaces. Albeit, the Action interface is not required. Any POJO object with a execute signature can be used as an Struts 2 Action object. 54
- 55. Threading Model Struts 1 Struts 2 Struts 1 Actions are singletons and Struts 2 Action objects are instantiated must be thread-safe since there will for each request, so there are no only be one instance of a class to thread-safety issues. (In practice, handle all requests for that Action. servlet containers generate many The singleton strategy places restrictions on what can be done throw-away objects per request, and with Struts 1 Actions and requires one more object does not impose a extra care to develop. Action performance penalty or impact resources must be thread-safe or garbage collection.) synchronized. 55
- 56. Action Classes Struts 1 Struts 2 Struts 1 requires Action classes to An Struts 2 Action may implement extend an abstract base class. A an Action interface, along with other common problem in Struts 1 is interfaces to enable optional and programming to abstract classes custom services. Struts 2 provides a instead of interfaces. base ActionSupport class to implement commonly used interfaces. Albeit, the Action interface is not required. Any POJO object with a execute signature can be used as an Struts 2 Action object. 56
- 57. Servlet Dependency Struts 1 Struts 2 Struts 1 Actions have dependencies Struts 2 Actions are not coupled to a on the servlet API since the container. Most often the servlet HttpServletRequest and contexts are represented as simple HttpServletResponse is passed to Maps, allowing Actions to be tested in the executemethod when an Action isolation. Struts 2 Actions can still access is invoked. the original request and response, if required. However, other architectural elements reduce or eliminate the need to access the HttpServetRequest or HttpServletResponse directly. 57
- 58. Testability Struts 1 Struts 2 A major hurdle to testing Struts 1 Struts 2 Actions can be tested by Actions is that theexecute method instantiating the Action, setting exposes the Servlet API. A third- properties, and invoking methods. party extension, Struts TestCase, Dependency Injection support also offers a set of mock object for Struts makes testing simpler. 1. 58
- 59. Harvesting Input Struts 1 Struts 2 Struts 1 uses an ActionForm object to Struts 2 uses Action properties as input capture input. Like Actions, all properties, eliminating the need for a second ActionForms must extend a base class. input object. Input properties may be rich object Since other JavaBeans cannot be used types which may have their own properties. The as ActionForms, developers often Action properties can be accessed from the create redundant classes to capture web page via the taglibs. Struts 2 also supports the ActionForm pattern, as well as POJO form input. DynaBeans can used as an objects and POJO Actions. Rich object types, alternative to creating conventional including business or domain objects, can be ActionForm classes, but, here too, used as input/output objects. The ModelDriven developers may be redescribing feature simplifies taglib references to POJO existing JavaBeans. input objects 59
- 60. Expression Language Struts 1 Struts 2 Struts 1 integrates with JSTL, so it Struts 2 can use JSTL, but the uses the JSTL EL. The EL has basic framework also supports a more object graph traversal, but relatively powerful and flexible expression weak collection and indexed language called "Object Graph property support. Notation Language" (OGNL). 60
- 61. Binding values into views Struts 1 Struts 2 Struts 1 uses the standard JSP Struts 2 uses a "ValueStack" mechanism for binding objects into technology so that the taglibs can the page context for access. access values without coupling your view to the object type it is rendering. The ValueStack strategy allows reuse of views across a range of types which may have the same property name but different property types 61
- 62. Type Conversion Struts 1 Struts 2 Struts 1 ActionForm properties are Struts 2 uses OGNL for type usually all Strings. Struts 1 uses conversion. The framework includes Commons-Beanutils for type converters for basic and common conversion. Converters are per-class, object types and primitives and not configurable per instance. 62
- 63. Validation Struts 1 Struts 2 Struts 1 supports manual validation Struts 2 supports manual validation via via a validatemethod on the the validate method and the XWork ActionForm, or through an extension Validation framework. The Xwork to the Commons Validator. Classes Validation Framework supports can have different validation contexts chaining validation into sub-properties for the same class, but cannot chain using the validations defined for the to validations on sub-objects. properties class type and the validation context. 63
- 64. Control of method execution Struts 1 Struts 2 Struts 1 supports separate Request Struts 2 supports creating different Processors (lifecycles) for each lifecycles on a per Action basis via module, but all the Actions in the Interceptor Stacks. Custom stacks can module must share the same be created and used with different lifecycle. Actions, as needed. 64
- 65. Other Differences Struts 1 Struts 2 Action Action ActionForm Action or POJO ActionForward Result struts-config.xml struts.xml ActionServlet FilterDispatcher RequestProcessor Interceptors validation.xml Action-validation.xml 65
- 66. Struts 2 Application Creating your first Struts 2 App 66
- 67. Scenario(s) 2 use cases Employee Attributes View list of Employees Add an Employee • Name • Age • Date of Birth • Gender • Country 67
- 68. Pre-requisite Need to have a following download and installed Java EE 1.5 Java SDK 1.7 Tomcat 7.0 Struts 2 libraries Database (like MySQL) Development environment (Eclipse) 68
- 69. Scenario 1 – View list of employees In the scenario, we will explore the following additional components Controller Actions Results 69
- 70. Scenario 1 – View list of employees – Step 1 Open Eclipse and create an dynamic web application project Add the struts jars to the class path Configuring the controller in the web.xml 70
- 71. Scenario 1 – View list of employees – Step 2a Next, we will define the Action class 71
- 72. Scenario 1 – View list of employees – Step 2b Next, we will define the Action 72
- 73. Scenario 1 – View list of employees – Step 3 Next, we will map the Action to the result in the struts.xml 73
- 74. Scenario 1 – View list of employees – Step 4 Next, we will see the viewEmp.jsp that was configured as the dispatcher jsp 74
- 75. Scenario 1 – View list of employees – Step 5 This completes all the steps in the scenario We compile and deploy the war file in the tomcat We hit the URL http://localhost:8080/Struts2Application/view.action 75
- 76. Scenario 2 – Add an Employee In the scenario, we will explore the following additional components Validations Field Non-Field Interceptors 76
- 77. Scenario 2 – Add an Employee – Step 1 Define the JSP page – addEmployee.jsp with the struts 2 tags 77
- 78. Scenario 2 – Add an Employee – Step 2 Define the Action class – AddEmployeeAction.java 78
- 79. Scenario 2 – Add an Employee – Step 2 Define the Action class – AddEmployeeAction.java 79
- 80. Scenario 2 – Add an Employee – Step 3 Next, lets define validation for the following fields as Age Mandatory Field Value should be between 18 and 60 Date of birth Mandatory Field Date format should be DD- MM-YYYY Name Mandatory field 80
- 81. Scenario 2 – Add an Employee – Step 3 Next, lets define validation for the following fields as Age Mandatory Field Value should be between 18 and 60 Date of birth Mandatory Field Date format should be DD- MM-YYYY Name Mandatory field 81
- 82. Scenario 2 – Add an Employee – Step 3 Next, lets define validation for the following fields as Age Mandatory Field Value should be between 18 and 60 Date of birth Mandatory Field Date format should be DD- MM-YYYY Name Mandatory field 82
- 83. Scenario 2 – Add an Employee – Step 3 Next, lets define validation for the following fields as Age Mandatory Field Value should be between 18 and 60 Date of birth Mandatory Field Date format should be DD- MM-YYYY Name Mandatory field 83
- 84. Scenario 2 – Add an Employee – Step 3 Next, lets define validation for the following fields as Age Mandatory Field Value should be between 18 and 60 Date of birth Mandatory Field Date format should be DD- MM-YYYY Name Mandatory field 84
- 85. Scenario 2 – Add an Employee – Step 4 Next , we will see the changes in the struts.xml 85
- 86. Scenario 2 – Add an Employee – Step 4 Next , we will see the changes in the struts.xml 86
- 87. Scenario 2 – Add an Employee – Step 5 Where is the validator interceptor defined? 87
- 88. Scenario 2 – Add an Employee – Step 5 How do I override the default ? 88
- 89. Scenario 2 – Add an Employee – Step 5 How do I override the default ? 89
- 90. Scenario 2 – Add an Employee – Step 5 How do I override the default ? 90
- 91. Scenario 2 – Add an Employee – Step 5 How do I override the default ? 91
- 92. Scenario 2 – Add an Employee – Step 6 Coming back to the Action class 92
- 93. Scenario 2 – Add an Employee – Step 7 So overall, we added or changed the following files Added AddEmployeeAction.java AddEmployeeAction-validation.xml AddEmployeeAction.properties addEmployee.jsp Changed Struts.xml 93
- 94. Scenario 2 – Add an Employee – Step 8 This completes all the steps in the scenario We compile and deploy the war file in the tomcat We hit the URL http://localhost:8080/Struts2Application/addEmp.action 94
- 95. Scenario 2 – Add an Employee – Step 9 Press Enter 95
- 96. Scenario 2 – Add an Employee – Step 9 Press Enter 96
- 97. Conclusion This concludes the programming demo Refer to struts 2 documentation for more in-depth details on each of the components 97
- 98. 98