examples/cdi-session-scope/README.adoc

= CDI @SessionScoped
:index-group: CDI
:jbake-type: page
:jbake-status: published

This example show the use of `@SessionScoped` annotation for injected objects. An object
which is defined as `@SessionScoped` is created once for every HTTPSession and is shared by all the
beans that inject it throughout the same HTTPSession.

== Run the application:

    mvn clean install tomee:run 
	
== Example

This example has an endpoint wherein a user provides a request parameter `name` which is persisted as a field in a session scoped bean `SessionBean` and 
then retrieved through another endpoint.

== Request

GET http://localhost:8080/cdi-session-scope/set-name?name=Puneeth

== Response

`done, go to /name servlet`

== Request

GET http://localhost:8080/cdi-session-scope/name

== Response

name = {Puneeth} 
 
== SessionBean

The annotation `@SessionScoped` specifies that a bean is session scoped ie there will be only one instance of the class associated with a particular HTTPSession.  

[source,java]
----
@SessionScoped
public class SessionBean implements Serializable {

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}  
----

== InputServlet

`InputServlet` is a generic servlet which is mapped to the url pattern `/set-name`.
The session scoped bean `SessionBean` has been injected into this servlet, and the incoming request parameter is set to the field `name` of the bean. 

[source,java]
----
@WebServlet(name = "input-servlet", urlPatterns = {"/set-name"})
public class InputServlet extends HttpServlet {

    @Inject
    private SessionBean bean;

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp 
    throws ServletException, IOException {
        final String name = req.getParameter("name");
        if (name == null || name.isEmpty()) {
            resp.getWriter().write("please add a parameter name=xxx");
        } else {
            bean.setName(name);
            resp.getWriter().write("done, go to /name servlet");
        }

    }
}
----

== AnswerBean

`AnswerBean` is a request scoped bean with an injected `SessionBean`. It has an `@PostConstruct` method 
wherein the value from the `SessionBean` is retrieved and set to a field.

[source,java]
----
public class AnswerBean {

    @Inject
    private SessionBean bean;

    private String value;

    @PostConstruct
    public void init() {
        value = '{' + bean.getName() + '}';
    }

    public String value() {
        return value;
    }
}
----

== OutputServlet

`OutputServlet` is another servlet with  `AnswerBean` as an injected field. When `/name` is called the value from `AnswerBean` is read and written to the response.

[source,java]
----
@WebServlet(name = "output-servlet", urlPatterns = {"/name"})
public class OutputServlet extends HttpServlet {

    @Inject
    private AnswerBean bean;

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp)
     throws ServletException, IOException {
        final String name = bean.value();
        if (name == null || name.isEmpty()) {
            resp.getWriter().write("please go to servlet /set-name please");
        } else {
            resp.getWriter().write("name = " + name);
        }
    }
}

----