user2407200 user2407200 - 6 months ago 6
Java Question

java.lang.NullPointerException when I try to access a page mapped to a Controller

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:

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)


Here the code of my
UserController.java:


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<String, Object> map) {

map.put("user", new User());
map.put("userList", userService.listAllUsers());

return "users";
}
}


UserService.java:


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<User> 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);
}

}


UserDao.java:


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<User> listUsers() {
// TODO Auto-generated method stub
return (List<User>)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);
}
}

}


User.java


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;
}


}


And my disparcher context
stbam-servlet.xml
:

<?xml version="1.0" encoding="UTF-8"?>
<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">

<context:annotation-config />
<context:component-scan base-package="com.gsimt.stbam" />

<bean id="jspViewResolver"
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView" />
<property name="prefix" value="/WEB-INF/views/" />
<property name="suffix" value=".jsp" />
</bean>

<bean id="messageSource"
class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
<property name="basename" value="classpath:messages" />
<property name="defaultEncoding" value="UTF-8" />
</bean>
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
p:location="/WEB-INF/configuration.properties" />



<tx:annotation-driven />

</beans>


And finally the
stbam-data.xml
where I'm configuring
datasource and sessionfactory
:

<?xml version="1.0" encoding="UTF-8"?>
<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">


<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" />


<!-- to use hibernate 4, we have to use at least spring 3.2.2 The AnnotationSessionFactoryBean

is not supported anymore and replaced by LocalSessionFactoryBean-->
<bean id="sessionFactory"
class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource"></property>
<property name="packagesToScan" value="com.gsimt.stbam.domain"></property>
<property name="hibernateProperties">
<value>
hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect
hibernate.hbm2ddl.auto=update
hibernate.show_sql=true
</value>
</property>
</bean>

<bean id="userDao"
class="com.gsimt.stbam.dao.UserDaoImpl" />



<bean id="transactionManager"
class="org.springframework.orm.hibernate4.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory"></property>
</bean>

</beans>


My web.xml:

<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">

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/stbam-service.xml
/WEB-INF/stbam-data.xml
/WEB-INF/stbam-security.xml
</param-value>
</context-param>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>

<servlet>
<servlet-name>stbam</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>detectAllViewResolvers</param-name>
<param-value>true</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>stbam</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>

</web-app>


I'v write a unit test to test the UserDao and UserService, and seems to be worhing fine,

Thanks in advance.




Just to clear things out, I'm using 3 spring configuration files:

stbam-data.xml for persistence.

stbam-service.xml for declaring services beans (including userServiceImpl).

The problem still here even when I add @Service and @Repositort("userDao")

Answer

Instead of

@Repository
public class UserDaoImpl implements UserDao{

use

@Repository("userDao")
public class UserDaoImpl implements UserDao{

By Defualt UserDaoImpl will have name userDaoImpl so its not autowiring.

And annotate UserServiceImpl with the @Service

Or add UserServiceImpl in Spring XML

Also if your using Spring Annotations you need not use same bean declarations in XML

Also just noticed you are not importing stbam-data.xml inside stbam-servlet.xml so If i am not wrong the file is not being used...

Try below in your stbam-servlet.xml

<import resource="classpath:stbam-data.xml" />

As per added web.xml file (you are missing COMMA ) Try with it.

<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            /WEB-INF/stbam-service.xml,
            /WEB-INF/stbam-data.xml,
            /WEB-INF/stbam-security.xml
        </param-value>

</context-param>
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