Spring dependency config problems - spring

Question

Hello guys,
I am new to Spring and currently I am working on a web project in which I use Spring MVC and Spring dependency injection. I have three classes. UserService, HomeController and User. In HomeController I invoke UserService's fetchUser method which returns me a new Instance of the User class. It is a simple logic I use to reproduce my real project problem. I am not using any database in this simple project. When I invoke the fetchUserMethod I am getting a NullPointerException. I am using Glassfish 4.0. Could you please help me ?
Thank you !
Here is my web.xml
`<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/aplicationContext.xml</param-value>
</context-param>
<!-- Creates the Spring Container shared by all Servlets and Filters -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<!-- Processes application requests -->
<servlet>
<servlet-name>appServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/servlet-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>appServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>`
Here is my applicationContext.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"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- Root Context: defines shared resources visible to all other web components -->
<bean id="userService" class="services.UserService"/>
<bean id="homeController" class="controllers.HomeController">
<property name="userService" ref="userService"/>
</bean>
</beans>
Here is my servlet-context.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:beans="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!-- Enables the Spring MVC #Controller programming model -->
<mvc:annotation-driven />
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/views/" />
<property name="suffix" value=".jsp" />
</bean>
<context:component-scan base-package="controllers"/>
</beans:beans>
Here is my HomeController class
#Controller
public class HomeController {
private UserService userService;
#RequestMapping(value = "/home")
public ModelAndView homePage(HttpServletRequest request, HttpServletResponse response, HttpSession session){
User user = userService.fetchUser();
return new ModelAndView("home", "displayName", user.getUserName());
}
public UserService getUserService() {
return userService;
}
public void setUserService(UserService userService) {
this.userService = userService;
}
}
Here is my User class
public class User {
private String userName;
private String password;
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
}
Here is my UserService class
public class UserService {
public User fetchUser(){
User user = new User();
user.setUserName("test");
return user;
}
}

Answer 1

You miss the #Autowired annotation in your HomeController:
#Autowired
private UserService userService;

Answer 2

Remove homeController bean defintiion.
Since you are using <context:component-scan base-package="controllers"/> there is no need to declare homeController bean - it will be created automatically because it's annotated with annotation #Controller.
Autowire UserService into HomeController using#Autowired` annotation. There are 3 ways you can do it:
field injection:
#Autowired
private UserService userService;
setter injection
#Autowired
public void setUserService(UserService userService) {
this.userService = userService;
}
constructor injection:
#Autowired
public HomeController(UserService userService) {
this.userService = userService;
}
Preferred way is to always use constructor injection
Remove UserService getters and setters in HomeController.
In the end, HomeController class should look like:
#Controller
public class HomeController {
private final UserService userService;
#Autowired
public HomeController(UserService userService) {
this.userService = userService;
}
#RequestMapping(value = "/home")
public ModelAndView homePage(HttpServletRequest request, HttpServletResponse response, HttpSession session){
User user = userService.fetchUser();
return new ModelAndView("home", "displayName", user.getUserName());
}
}

Answer 3

This way Eclipse marks the default constructor line with error. If I remove the default constructor glassfish says it cannot initialize UserService because there is no default constructor.
public class UserService {
public UserService(){}
private final UserDao userDao;
#Autowired
public UserService(UserDao userDao){
this.userDao = userDao;
}
public User fetchUser(){
User user = userDao.fetchUser();
return user;
}
}