DI in servlet

[Kiril Nugmanov]

Hi all,


Currently i'm preparing for the SCBCD5 (have minor expirience with EJB). I'm really confused with DI in EJB3 - trying to acces local EJB from servlet and allways getting NullPointerException.

09:42:27,078 ERROR [[jsp]] Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
	at lt.emc.servlet.EjbAccess.doGet(EjbAccess.java:22)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:638)
	at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:444)
	at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:382)
	at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:310)
	at org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:696)
	at org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:667)
	at org.apache.jsp.index_jsp._jspService(index_jsp.java:55)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:322)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:249)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:235)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:183)
	at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:95)
	at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.process(SecurityContextEstablishmentValve.java:126)
	at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:70)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:158)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:330)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:829)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:598)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:619)    

Was trying with several application servers Galssfish 2.1.1/3, JBoss 6.0.0.1. JDK version 1.6.0_18

There is my files:

Local interface

package lt.emc.ejb;

import javax.ejb.Local;

@Local
public interface Hello {
    public String sayHello(String name);
}
   

EJB

package lt.emc.ejb;

import javax.ejb.Stateless;

@Stateless(name = "HelloEJB")
public class HelloBean implements Hello {
    public String sayHello(String name) {
        return "Hello " + name + "!";
    }
}
    

Servlet

package lt.emc.servlet;

import lt.emc.ejb.Hello;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import javax.servlet.RequestDispatcher;
import javax.ejb.EJB;
import java.io.IOException;

import org.omg.CORBA.Request;

public class EjbAccess extends HttpServlet {
    @EJB(name = "HelloEJB")
    private Hello hello;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        RequestDispatcher disp = request.getRequestDispatcher("/result.jsp");

        request.setAttribute("result", hello.sayHello("Duke"));

        disp.forward(request, response);
    }
}
    

DD

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <servlet>
        <servlet-name>EjbAccess</servlet-name>
        <servlet-class>lt.emc.servlet.EjbAccess</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>EjbAccess</servlet-name>
        <url-pattern>/ejb</url-pattern>
    </servlet-mapping>
</web-app>
   

Maybe I'm missing something...

[Jaikiran Pai]

Kiril Nugmanov wrote:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
         xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    
   

Web-app 2.4 doesn't support injection. You will need 2.5 version of the xsd. See this http://www.coderanch.com/t/426854/EJB-Other-Java-EE-Technologies/java/EJB-doing-nothing-jboss-GA#1894841

[Kiril Nugmanov]

Hi Jaikiran Pai,

Thats was the problem. Thank you.