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Editorial Team
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Asked: 2026-06-11T07:44:29+00:00

I’m moving my knowledge to spring and I dont really get how this is

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I’m moving my knowledge to spring and I dont really get how this is working. I’m trying to make a very basic example to make it work, but I couldn’t make it work :-((

ApplicationContext.xml

<bean id="serviceTest" class="es.mov.jose.agenda.ServiceTest">
</bean>

    <bean id="serviceMovility" class="es.mov.jose.agenda.ServiceMovility">
    <property name="serviceTest" ref="serviceTest" />
</bean>

    <bean name="/jose/req1.do" class="org.springframework.web.servlet.mvc.ParameterizableViewController">
    <property name="viewName" value="jose/req1" />
</bean>

ServiceMovility.java

package es.mov.jose.agenda;

public interface ServiceMovility {
        public String callTest();
}

ServiceMovilityImpl.java

package es.mov.jose.agenda;

import es.mov.jose.agenda.ServiceMovility;

public class ServiceMovilityImpl implements ServiceMovility {

    private ServiceTest serviceTest;    
    public String callTest() {
        return serviceTest.getValue();
    }

}

ServiceTest.java

package es.mov.jose.agenda;

public interface ServiceTest {
        public String getValue();
}

ServiceTestImpl.java

package es.mov.jose.agenda;

import es.mov.jose.agenda.ServiceTest;

public class ServiceTestImpl implements ServiceTest {

    public String getValue() {
        return "OK";
    }

}

and finally my req1.jsp 

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@ page import="es.mov.jose.agenda.ServiceMovility"%>
<%@ page import="es.mov.jose.agenda.ServiceMovilityImpl"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<%@ taglib prefix="sp-forms" uri="http://www.springframework.org/tags/form"%>
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">    
</head>
<body>
<jsp:useBean id="serviceMovility" scope="request"     class="es.mov.jose.agenda.ServiceMovilityImpl" />
<div class="main" >
    <%
    String result = serviceMovility.callTest();
    out.println(result);
    %>
</div>
</body>
</html>

It call serviceMovility perfectly but fail calling serviceTest inside callTest method, it says java.lang.NullPointerException
¿Should I include the bean serviceMovility in that way in jsp file? ¿Why spring doesn’t inject serviceTest initialized on serviceMovility?

I spent 2 days on this but I failed on all my solutions. I don’t know what to do.

Thanks in advance.

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1 Answer

  1. Editorial Team

    Use implementations instead of interfaces while defining beans:

    <bean id="serviceTest" class="es.mov.jose.agenda.ServiceTestImpl" />

<bean id="serviceMovility" class="es.mov.jose.agenda.ServiceMovilityImpl">
  <property name="serviceTest" ref="serviceTest" />
</bean>

<bean name="/jose/req1.do"
    class="es.mov.jose.agenda.Req1Controller">
  <property name="viewName" value="jose/req1" />
  <property name="serviceMovility" ref="serviceMovility" />
</bean>

    plus, in your *Impl classes define setters to injected dependencies, i.e. in ServiceMovilityImpl:

    public void setServiceTest(ServiceTest serviceTest) {
  this.serviceTest = serviceTest;
}

    EDIT:

    You’re doing it wrong… Don’t inject beans into JSP (via jsp:useBean), but directly to Controller. Define your own controller:

    package es.mov.jose.agenda;

final class Req1Controller extends ParameterizableViewController {

  private ServiceMovility serviceMovility;

  @Override
  protected ModelAndView handleRequestInternal(HttpServletRequest request,
      HttpServletResponse response) throws Exception {
    ModelAndView mav = new ModelAndView(getViewName());
    mav.addObject("callTest", serviceMovility.callTest());
    return mav;
  }

  public void setServiceMovility(ServiceMovility serviceMovility) {
    this.serviceMovility = serviceMovility;
  }
}

    Edit your ApplicationContext.xml as I did above (use Req1Controller instead ParameterizableViewController), and in JSP you’ll have ${callTest} variable:

    <body>
  <div class="main" >
    <c:out value="${callTest}" />
  </div>
</body>
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