java.lang.NullPointerException when I try to access a page mapped to a Controller
Solution 1
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>
Solution 2
Annotate your UserServiceImpl
with the @Service
stereotype so that it becomes eligible for autowiring.
Admin
Updated on August 01, 2022Comments
-
Admin almost 2 years
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 configuringdatasource 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")
-
rahul maindargi almost 11 yearsas per OPs stackTrace exception coming at
com.gsimt.stbam.service.UserServiceImpl.listAllUsers(UserServiceImpl.java:16)
that means code reaching till 'UserServiceImpl' -
Admin almost 11 yearsYes you are right, but I'v used a unit test and the function seems working
-
nightfury about 5 yearsI tried doing this but not working for me ? any other work around - I am getting fed up of this error - my elaborated question is here -stackoverflow.com/questions/55196698/… - please check if you have any fix, Thanks