Developing web apps using Java and the Play framework
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The document discusses developing web applications using the Play framework with Java. It describes Play as a clean alternative to Java Enterprise Edition that uses a pure Java framework. Play uses the MVC architecture with classes as models, the application as the controller, and generated HTML as the view. It allows binding URI patterns to Java calls and uses an efficient Groovy template engine to render HTML responses. Key features of Play discussed include hot-reloading of code without server restarts, easy error handling, support for JPA/JPQL, integrated caching, and web services consumption. The document also provides examples of common tasks in Play like binding HTTP parameters, file uploads, and redirecting between actions.
Developing web apps using Java and the Play framework
- 1. developing web applications using Java and the Play framework
- 2. What is Play?A clean alternative to the bloated Java Enterprise EditionPure Java framework – allows you to keep your preferred development tools and librariesFocuses on developer productivity and targets RESTful(Representational State Transfer) architecturesConsist of clients and serversClients initiate requests to serversServers process requests and return appropriate responsesRequests and responses are built around the transfer of representations of resources
- 3. The foundation of PlayMVC architectureYou’ve got a database on one side and a web browser on the other.Classes are models, the application is the controller, generated HTML is the viewHTTP-to-code mappingExample: binding URI patterns to Java procedure callsEfficient template engineThe expression language used is GroovyTemplating system mainly used to render HTML responses
- 4. Why is play awesome?Fix the bug and hit reloadThe framework compiles your Java sources directly and hot-reloads them into the JVM without the need to restart the serverYou can then edit, reload and see your modifications immediately, just as in a Rails environmentWhenever an error occurs, the framework identifies and shows you the problemStack traces are stripped down and optimized to make it easier to solve problemsJava Persistence API (JPA) and The Java Persistence Query Language (JPQL) A persistence entity is a lightweight Java class saved to a table in a relational database.
- 5. JPA, JPQL// Java Persistence API example@Entity public class Book { @Id private Integer id; private String title; private String isbn; @ManyToOne private Publisher publisher; @ManyToManyprivate List<Author> authors; }
- 6. JPA, JPQL// Java Persistence Query Language examplepublic void messages(intpage, User connectedUser) {List<Message> messages = Message.find(“ user = ? and read = false order by date desc", connectedUser).from(page * 10).fetch(10); render(connectedUser, messages); }
- 7. Why is play awesome?Test-driven developmentRun them directly in a browser using SeleniumSelenium is a Firefox add-on that records clicks, typing, and other actionsDatabase support through JDBCObject-relational mapping using Hibernate (with the JPA API)Integrated cache supportStraightforward web services consumption either in JSON or XMLOpenIDsupport for distributed authenticationReady to be deployed anywhere (application server, Google App Engine, Cloud, etc…)Image manipulation API.
- 8. Things you can do with play
- 9. Things you can do with playBind an HTTP parameter to a Java method parameter// a simple request/articles/archive?date=08/01/08&page=2// the Java methodpublic staticvoid archive(Date date, Integer page) { List<Article> articles = Articles.fromArchive(date, page); render(articles); }
- 10. Things you can do with playSmart binding with any class// a simple modelpublic class Person { public String name; public Integer age; }// a simple controllerpublic static void add(Person p) { p.save(); }// a simple HTML form<form action="add" method="POST"> Name: <input type="text" name="p.name" /> Age: <input type="text" name="p.age" /> </form>
- 11. Things you can do with playRedirect to an action by calling the corresponding Java method// a simple model with a procedurepublic static void show(Long id) { Article article = Article.findById(id); render(article); }// use the equivalent syntax:<a href="@{Article.show(article.id)}">${article.title}</a>
- 12. Things you can do with playRedirect to an action by calling the corresponding Java method (another example)// a simple model with a procedurepublic static void edit(Long id, String title) { Article article = Article.findById(id); article.title= title; article.save();show(id); }// generated HTML:<a href="/articles/15">My new article</a>
- 13. Things you can do with playStraightforward file upload management// the Java codepublic static void uploadPhoto(String title, File photo) { ... }// a simple HTML form<form action="@{Article.uploadPhoto()}" method="POST" enctype="multipart/form-data"> <input type="text" name="title" /> <input type="file" id="photo" name="photo" /> <input type="submit" value="Send it..." /></form>
- 14. DEMOLet’s create our own web application: a personal agenda
- 15. Questions?