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CDI @SessionScoped

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.

@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.

@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.

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.

@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);
        }
    }
}

APIs Used