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JBoss Seam: Contextual Components

JBoss Seam: Contextual Components. Jason Bechtel bechtel2@cse.buffalo.edu. Overview. What is Seam? How does it work? Example Code and what it does Demo How it works Questions. What is JBoss Seam?. An application framework for Java EE 5 A unifier for EJB 3.0 and JSF

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JBoss Seam: Contextual Components

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  1. JBoss Seam: Contextual Components Jason Bechtel bechtel2@cse.buffalo.edu

  2. Overview • What is Seam? • How does it work? • Example Code and what it does • Demo • How it works • Questions

  3. What is JBoss Seam? • An application framework for Java EE 5 • A unifier for EJB 3.0 and JSF • Integrates the server layer with the presentation layer • Declarative State Management

  4. What is JBoss Seam? • Seam works in any application server that supports EJB 3.0 • Use Seam as a framework for applications using • JSF (Presentation) • Hibernate (or plain JDBC) (Persistence) • JavaBeans (Business Logic) • Etc.

  5. How does it work? • 2 JSP pages • An Entity Bean • A Stateless Session Bean • EJB Entity management • Uses EJB Session Beans as JSF Action Listeners (no “glue code”) • No JNDI context lookup • Seam does it all!

  6. @Entity (1) @Name("user") (2) @Scope(SESSION) (3) @Table(name="users") (4) public class User implements Serializable { private static final long serialVersionUID = 1881413500711441951L; private String username; (5) private String password; private String name; public User(String name, String password, String username) { this.name = name; this.password = password; this.username = username; } User.java (Entity Bean)

  7. (1)The EJB3 standard @Entity annotation indicates that the User class is an entity bean. • (2)A Seam component needs a component name specified by the @Name annotation. This name must be unique within the Seam application. When JSF asks Seam to resolve a context variable with a name that is the same as a Seam component name, and the context variable is currently undefined (null), Seam will instantiate that component, and bind the new instance to the context variable. In this case, Seam will instantiate a User the first time JSF encounters a variable named user. • (3)Whenever Seam instantiates a component, it binds the new instance to a context variable in the component's default context. The default context is specified using the @Scope annotation. The User bean is a session scoped component. • (4)The EJB standard @Table annotation indicates that the User class is mapped to the users table. • (5)name, password and username are the persistent attributes of the entity bean. All of our persistent attributes define accessor methods. These are needed when this component is used by JSF in the render response and update model values phases.

  8. User.java Con’t • public User() {} (6) • @NotNull • @Length(min=5, max=15) (7) • public String getPassword() { return password; } • public void setPassword(String password) { this.password = password; } • @NotNull • public String getName() { return name; } • public void setName(String name) { this.name = name;} • @Id • @NotNull • @Length(min=5, max=15) (8) • public String getUsername() { return username; } • public void setUsername(String username) { this.username = username; } • }

  9. (6)An empty constructor is both required by both the EJB specification and by Seam. • (7)The @NotNull and @Length annotations are part of the Hibernate Validator framework. Seam integrates Hibernate Validator and lets you use it for data validation (even if you are not using Hibernate for persistence). • (8)The EJB standard @Id annotation indicates the primary key attribute of the entity bean.

  10. RegistrationAction.java (Session Bean) • @Stateless (1) • @Name("register") • @Interceptors(SeamInterceptor.class) (2) • public class RegisterAction implements Register { • @In(3) • @Valid (4) • private User user; • @PersistenceContext (5) • private EntityManager em; • @In private • FacesContext facesContext; (6) • @IfInvalid(outcome=Outcome.REDISPLAY) (7) • public String register() { (8) • List existing = em.createQuery("select username …..

  11. (1)The EJB standard @Stateless annotation. • (2)The SeamInterceptor EJB interceptor must be enabled for all session beans which are Seam components. • (3)The @In annotation marks an attribute of the bean as injected by Seam. In this case, the attribute is injected from a context variable named user (the instance variable name). • (4)The @Valid annotation is provided by Hibernate Validator. • (5)The EJB standard @PersistenceContext annotation. • (6)Seam also allows various JSF, Seam and jBPM context objects to be injected. To get the current FacesContext instance injected to a Seam component, just mark an instance variable named facesContext with the @In annotation. • (7)The @IfInvalid annotation tells Seam to validate the component state using Hibernate Validator before invoking the action listener method, and return a different JSF outcome if the state is invalid. In this example, the user is validated when the register() method is invoked, and the form is redisplayed with messages if a validation failure occurs. • (8)The action listener method uses the standard EJB3 EntityManager API to interact with the database, and returns the JSF outcome. Note that, since this is a sesson bean, a transaction is automatically begun when the register() method is called, and committed when it completes.

  12. faces-config.xml • <?xml version="1.0" encoding="UTF-8"?> • <!DOCTYPE faces-config • PUBLIC "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN" "http://java.sun.com/dtd/web-facesconfig_1_0.dtd"> • <faces-config> • <navigation-rule> • <navigation-case> • <from-outcome>success</from-outcome> • <to-view-id>/registered.jsp</to-view-id> </navigation-case> • </navigation-rule> • <!-- A phase listener is needed by all Seam applications --> • <lifecycle> • <phase-listener>org.jboss.seam.jsf.SeamPhaseListener • </phase-listener> • </lifecycle> • </faces-config>

  13. <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <html> <head> <title> Register New User </title> </head> <body> <f:view> <h:form> <table border="0"> <tr> <td>Username</td> <td><h:inputText value="#{user.username}"/></td> </tr> <tr> <td>Real Name</td> <td><h:inputText value="#{user.name}"/></td> </tr> <tr> <td>Password</td> <td><h:inputSecret value="#{user.password}"/></td> </tr> </table> <h:messages/> <h:commandButton type="submit" value="Register" action="#{register.register}"/> </h:form> </f:view> </body> </html> <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %> <html> <head> <title> Successfully Registered New User </title> </head> <body> <f:view> Welcome, <h:outputText value="#{user.name}"/> , you are successfully registered as <h:outputText value="#{user.username}"/> </f:view> </body> </html> View pages using JSP with JSF

  14. application.xml • <application> • <display-name>Seam</display-name> • <module> • <web> • <web-uri>jboss-seam-registration.war</web-uri> • <context-root>/seam-registration</context-root> • </web> • </module> • <module> • <ejb>jboss-seam-registration.jar</ejb> • </module> • </application> • This deployment descriptor links modules in the enterprise archive and binds the web application to the context root /seam-registration. • We've now seen most of the files in the application!

  15. Demo

  16. How it works • When the form is submitted, JSF asks Seam to resolve the variable named user. Since there is no value already bound to that name (in any Seam context), Seam instantiates the user component, and returns the resulting User entity bean instance to JSF after storing it in the Seam session context. JSF binds the form input values to properties of the User entity bean. • Next, JSF asks Seam to resolve the variable named register. Seam finds the RegisterAction stateless session bean in the stateless context and returns it. JSF invokes the register() action listener method. • Seam intercepts the method call, injects the User entity from the session context, and the current FacesContext instance, before asking Hibernate Validator to validate the session bean instance (and, recursively, the User entity bean instance). If the state is valid, the invocation proceeds and the register() method is called. If not, Seam returns a null outcome and JSF redisplays the page. • When JSF comes to render the next JSP page, it asks Seam to resolve the variable named user and uses property values of the returned User entity from Seam's session scope.

  17. References • http://labs.jboss.com/portal/index.html?ctrl:id=page.default.info&project=jbossseam • http://labs.jboss.com/portal/jbossseam/gettingstarted • http://docs.jboss.com/seam/reference/en/html/index.html

  18. Questions?

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