title: java.lang.NullPointerException when I try to access a page mapped to a Controller
body: <p>I'm coding an application in spring 3 and hibernate, when I try to access a "users" jsp page mapped to the "UserController" controller I get an exception:</p>
  
  <pre><code>SEVERE: Servlet.service() for servlet [stbam] in context with path [/STBAM] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
  java.lang.NullPointerException
      at com.gsimt.stbam.service.UserServiceImpl.listAllUsers(UserServiceImpl.java:16)
      at com.gsimt.stbam.controller.UserController.listUsers(UserController.java:24)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
      at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:440)
      at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:428)
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
      at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
      at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1001)
      at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
      at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
      at java.lang.Thread.run(Unknown Source)
  </code></pre>
  
  <p>Here the code of my <code>UserController.java:</code></p>
  
  <pre><code>package com.gsimt.stbam.controller;
  
  import java.util.List;
  import java.util.Map;
  
  import org.springframework.stereotype.Controller;
  import com.gsimt.stbam.domain.User;
  import com.gsimt.stbam.service.UserService;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.web.bind.annotation.RequestMapping;
  import org.springframework.web.bind.annotation.RequestMethod;
  import org.springframework.web.servlet.ModelAndView;
  
  @Controller
  public class UserController {
  
      @Autowired
      private UserService userService;
  
       @RequestMapping("/users")
          public String listUsers(Map&lt;String, Object&gt; map) {
  
              map.put("user", new User());
              map.put("userList", userService.listAllUsers());
  
              return "users";
          }
  }
  </code></pre>
  
  <p><code>UserService.java:</code></p>
  
  <pre><code>package com.gsimt.stbam.service;
  
  import java.util.List;
  
  import com.gsimt.stbam.domain.User;
  import com.gsimt.stbam.dao.UserDao;
  import org.springframework.beans.factory.annotation.Autowired;
  
  public class UserServiceImpl implements UserService {
  
      @Autowired
      private UserDao userDao;
  
      public List&lt;User&gt; listAllUsers() {
          // TODO Auto-generated method stub
          return userDao.listUsers();
      }
  
      public User getUserById(Integer Id) {
          // TODO Auto-generated method stub
          return userDao.getUserById(Id);
      }
  
      public void addUser(User user) {
          // TODO Auto-generated method stub
          userDao.addOrUpdateUser(user);
      }
  
      public void deleteUser(Integer Id) {
          // TODO Auto-generated method stub
          userDao.deleteUser(Id);
      }
  
  }
  </code></pre>
  
  <p><code>UserDao.java:</code></p>
  
  <pre><code>package com.gsimt.stbam.dao;
  
  import java.util.List;
  
  import com.gsimt.stbam.domain.User;
  
  import org.hibernate.SessionFactory;
  import org.springframework.stereotype.Repository;
  import org.springframework.beans.factory.annotation.Autowired;
  
  @Repository
  public class UserDaoImpl implements UserDao{
  
      @Autowired
      private SessionFactory sessionFactory;
  
      public List&lt;User&gt; listUsers() {
          // TODO Auto-generated method stub
          return (List&lt;User&gt;)sessionFactory.getCurrentSession().createQuery("from User").list();
      }
  
      public User getUserById(Integer Id) {
          // TODO Auto-generated method stub
          User user = (User) sessionFactory.getCurrentSession().load(User.class, Id);
          return user;
      }
  
      public void addOrUpdateUser(User user) {
          // TODO Auto-generated method stub
          sessionFactory.getCurrentSession().saveOrUpdate(user);
      }
  
      public void deleteUser(Integer Id) {
          // TODO Auto-generated method stub
          User user = (User) sessionFactory.getCurrentSession().load(User.class, Id);
          if(user != null){
  
              sessionFactory.getCurrentSession().delete(user);
          }
      }
  
  }
  </code></pre>
  
  <p><code>User.java</code></p>
  
  <pre><code>package com.gsimt.stbam.domain;
  
  import java.io.Serializable;
  
  import javax.persistence.Entity;
  import javax.persistence.GeneratedValue;
  import javax.persistence.GenerationType;
  import javax.persistence.Table;
  import javax.persistence.Id;
  import javax.persistence.Column;
  
  @Entity
  @Table (name = "USER")
  public class User implements Serializable{
  
      /**
       * 
       */
      private static final long serialVersionUID = 1L;
  
      @Id
      @Column (name = "ID")
      @GeneratedValue(strategy=GenerationType.AUTO)
      private Integer Id;
  
      @Column (name = "LOGIN")
      private String login;
  
      @Column (name = "FIRSTNAME")
      private String firstName;
  
      @Column (name = "LASTNAME")
      private String lastName;
  
      @Column (name = "EMAIL")
      private String email;
  
      @Column (name = "HASH")
      private String hash;
  
      public Integer getId() {
          return Id;
      }
  
      public void setId(Integer id) {
          Id = id;
      }
  
      public String getLogin() {
          return login;
      }
  
      public void setLogin(String login) {
          this.login = login;
      }
  
      public String getFirstName() {
          return firstName;
      }
  
      public void setFirstName(String firstName) {
          this.firstName = firstName;
      }
  
      public String getLastName() {
          return lastName;
      }
  
      public void setLastName(String lastName) {
          this.lastName = lastName;
      }
  
      public String getEmail() {
          return email;
      }
  
      public void setEmail(String email) {
          this.email = email;
      }
  
      public String getHash() {
          return hash;
      }
  
      public void setHash(String hash) {
          this.hash = hash;
      }
  
  
  }
  </code></pre>
  
  <p>And my disparcher context <code>stbam-servlet.xml</code>:</p>
  
  <pre><code>&lt;?xml  version="1.0" encoding="UTF-8"?&gt;
  &lt;beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:aop="http://www.springframework.org/schema/aop"
      xmlns:context="http://www.springframework.org/schema/context"
      xmlns:jee="http://www.springframework.org/schema/jee"
      xmlns:lang="http://www.springframework.org/schema/lang"
      xmlns:p="http://www.springframework.org/schema/p"
      xmlns:tx="http://www.springframework.org/schema/tx"
      xmlns:util="http://www.springframework.org/schema/util"
      xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
          http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
          http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
          http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd
          http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang.xsd
          http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
          http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd"&gt;
  
      &lt;context:annotation-config /&gt;
      &lt;context:component-scan base-package="com.gsimt.stbam" /&gt;
  
      &lt;bean id="jspViewResolver"
          class="org.springframework.web.servlet.view.InternalResourceViewResolver"&gt;
          &lt;property name="viewClass"
              value="org.springframework.web.servlet.view.JstlView" /&gt;
          &lt;property name="prefix" value="/WEB-INF/views/" /&gt;
          &lt;property name="suffix" value=".jsp" /&gt;
      &lt;/bean&gt;
  
      &lt;bean id="messageSource"
          class="org.springframework.context.support.ReloadableResourceBundleMessageSource"&gt;
          &lt;property name="basename" value="classpath:messages" /&gt;
          &lt;property name="defaultEncoding" value="UTF-8" /&gt;
      &lt;/bean&gt;
      &lt;bean id="propertyConfigurer"
          class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
          p:location="/WEB-INF/configuration.properties" /&gt;
  
  
  
      &lt;tx:annotation-driven /&gt;
  
  &lt;/beans&gt;
  </code></pre>
  
  <p>And finally the <code>stbam-data.xml</code> where I'm configuring <code>datasource and sessionfactory</code>:</p>
  
  <pre><code>&lt;?xml  version="1.0" encoding="UTF-8"?&gt;
  &lt;beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:aop="http://www.springframework.org/schema/aop"
      xmlns:context="http://www.springframework.org/schema/context"
      xmlns:jee="http://www.springframework.org/schema/jee"
      xmlns:lang="http://www.springframework.org/schema/lang"
      xmlns:p="http://www.springframework.org/schema/p"
      xmlns:tx="http://www.springframework.org/schema/tx"
      xmlns:util="http://www.springframework.org/schema/util"
      xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
          http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
          http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
          http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd
          http://www.springframework.org/schema/lang http://www.springframework.org/schema/lang/spring-lang.xsd
          http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
          http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd"&gt;
  
  
    &lt;bean id="dataSource"
          class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"
          p:driverClassName="com.mysql.jdbc.Driver"
          p:url="jdbc:mysql://localhost:3306/STBAMDB" p:username="root"
          p:password="123456" /&gt;
  
  
      &lt;!-- to use hibernate 4, we have to use at least spring 3.2.2 The AnnotationSessionFactoryBean
  
      is not supported anymore and replaced by LocalSessionFactoryBean--&gt;
      &lt;bean id="sessionFactory"
            class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"&gt;
              &lt;property name="dataSource" ref="dataSource"&gt;&lt;/property&gt;
              &lt;property name="packagesToScan" value="com.gsimt.stbam.domain"&gt;&lt;/property&gt;
              &lt;property name="hibernateProperties"&gt;
                   &lt;value&gt;
                      hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
                      hibernate.hbm2ddl.auto=update
                      hibernate.show_sql=true
                  &lt;/value&gt;
             &lt;/property&gt;    
     &lt;/bean&gt;
  
     &lt;bean id="userDao"
           class="com.gsimt.stbam.dao.UserDaoImpl" /&gt;
  
  
  
  &lt;bean id="transactionManager" 
    class="org.springframework.orm.hibernate4.HibernateTransactionManager"&gt;
      &lt;property name="sessionFactory" ref="sessionFactory"&gt;&lt;/property&gt;
  &lt;/bean&gt;
  
    &lt;/beans&gt;
  </code></pre>
  
  <p>My web.xml:</p>
  
  <pre><code>&lt;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"&gt;
  
      &lt;context-param&gt;
          &lt;param-name&gt;contextConfigLocation&lt;/param-name&gt;
          &lt;param-value&gt;
              /WEB-INF/stbam-service.xml
              /WEB-INF/stbam-data.xml
              /WEB-INF/stbam-security.xml
          &lt;/param-value&gt;
      &lt;/context-param&gt;
  
      &lt;listener&gt;
          &lt;listener-class&gt;org.springframework.web.context.ContextLoaderListener&lt;/listener-class&gt;
      &lt;/listener&gt;
  
      &lt;listener&gt;
          &lt;listener-class&gt;org.springframework.web.util.Log4jConfigListener&lt;/listener-class&gt;
      &lt;/listener&gt;
  
      &lt;servlet&gt;
          &lt;servlet-name&gt;stbam&lt;/servlet-name&gt;
          &lt;servlet-class&gt;org.springframework.web.servlet.DispatcherServlet&lt;/servlet-class&gt;
          &lt;init-param&gt;
              &lt;param-name&gt;detectAllViewResolvers&lt;/param-name&gt;
              &lt;param-value&gt;true&lt;/param-value&gt;
          &lt;/init-param&gt;
          &lt;load-on-startup&gt;1&lt;/load-on-startup&gt;
      &lt;/servlet&gt;
  
      &lt;servlet-mapping&gt;
          &lt;servlet-name&gt;stbam&lt;/servlet-name&gt;
          &lt;url-pattern&gt;/&lt;/url-pattern&gt;
      &lt;/servlet-mapping&gt;
  
  &lt;/web-app&gt;
  </code></pre>
  
  <p>I'v write a unit test to test the UserDao and UserService, and seems to be worhing fine,</p>
  
  <p>Thanks in advance.</p>
  
  <hr>
  
  <p>Just to clear things out, I'm using 3 spring configuration files:</p>
  
  <p>stbam-data.xml for persistence.</p>
  
  <p>stbam-service.xml for declaring services beans (including userServiceImpl).</p>
  
  <p>The problem still here even when I add @Service and @Repositort("userDao")</p>