Spring Autowiring is not happening ? Object is not initializing at all

Question

We are using Spring MCV and i am trying to use spring auto wiring to decouple my code. however, autowiring is not happening at all. Can you please suggest any issue in following code/ dispatcher

dispatcher-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
           xsi:schemaLocation="http://www.springframework.org/schema/beans
               http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
               http://www.springframework.org/schema/mvc
               http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd
               http://www.springframework.org/schema/context
               http://www.springframework.org/schema/context/spring-context-4.1.xsd"
           xmlns:context="http://www.springframework.org/schema/context">
        <context:component-scan base-package="com.eos.accounts" />
    </beans>

User.java

package com.eos.accounts.data;
@Service
public class User {
.......
    @Autowired
    public UserMilesHelper  userMilesHelper             ;
.....
public static setUserPoints(User user){
 user.setPoints(user.userMilesHelper.getUserPoints(user.getUserId()));
}

IUserMilesHelper.java

package com.eos.accounts.data;

public interface IUserMilesHelper {

    public int getUserPoints(int userId);

}

UserMilesHelper.java

    package com.eos.accounts.data;

    import org.springframework.stereotype.Component;
   //I have used @Repository or Qualifier etc, no avail 
    @Component
    public class UserMilesHelper implements IUserMilesHelper {

        @Override
        public int getUserPoints(int userId) {
            return 10;
        }

    }

Web.xml

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>throwExceptionIfNoHandlerFound</param-name>
        <param-value>true</param-value>
    </init-param>
    <load-on-startup>50</load-on-startup>
</servlet>

@BaptisteBeauvais normal calling, while calling the function. not instantiated by spring. not sure how to instantiate user. As far i know spring scans the package(com.eos.accounts) and check for 'autowired' and 'Components' and initialises objects while loading without caring about User.java(Not sure) — Mukesh Kumar, Sep 18 '17 at 07:00
Yes exactly, but as Spring doesn't instantiate the User he can't inject the dependancy you want. — Baptiste Beauvais, Sep 18 '17 at 07:09

score 0 · Answer 1 · answered Sep 18 '17 at 06:54

0

your User.java class have to be annotated with @Component too or any of its children for ex.

@Controller @Service @RestController

answered Sep 18 '17 at 06:54

Bassem Reda Zohdy

12,662
3
33
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Done that too. added @Service for User.java. still same issue. Pls suggest – Mukesh Kumar Sep 18 '17 at 07:07
please share all application context files you have and how are you configure Servlet-Dispatcher.xml in web descriptor. – Bassem Reda Zohdy Sep 18 '17 at 07:21
Also show us how you instantiate the `User` class in your code. It may be annotated with `@Service` but if you instantiate it with `new User()` autowiring wont work. – pleft Sep 18 '17 at 07:23
Updated question with web.xml where we are using dispatcher and yes i'm using new User(). pls suggest any solution autowiring even if i am doing new User(), how can we do that ? – Mukesh Kumar Sep 18 '17 at 07:30
1

If you are using `new User()` autowiring wont work., You have to get the `User` object from Spring context. – pleft Sep 18 '17 at 07:45
And where is your controller ? – Bassem Reda Zohdy Sep 18 '17 at 07:48
As mentioned earlier, there is not @controller. we have only told spring about component scan package, autowired and component. – Mukesh Kumar Sep 18 '17 at 12:41
I used `@Controller` `@Service` `@Congiguration` on `User.java`, still no avail – Mukesh Kumar Sep 19 '17 at 06:41
if you are not using controller so you have to get user from context like `applicationContext.getBean("User");` – Bassem Reda Zohdy Sep 19 '17 at 06:56
and get context as `ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");` – Bassem Reda Zohdy Sep 19 '17 at 07:01

score 0 · Answer 2 · answered Sep 18 '17 at 07:41

0

Spring initiliaze component in his context by scanning packages and looking for class annoted with stereotypes (@Controller, @Service, @Repository....) or by explicit instantiation with manually adding a bean. If you use a the new it won't call Spring initilization mecanism and won't inject the dependancy.

I suppose your User class is not a singleton class so you should add @Scope("prototype") and use applicationContext.getBean(User.class) to instantiate with dependancy.

But to be honest i would instead refactor the code to avoid public members and static method to set variable and have class like that:

@Service
public class UserService{

   private IUserMilesHelper userHelper;

   @Autowired
   public UserService(IUserMilesHelper userHelper){
       this.userHelper = userHelper:
   }

   public setUserPoints(User user){
      user.setPoints(userHelper.getUserPoints(user.getUserId()));
   }
}

answered Sep 18 '17 at 07:41

Baptiste Beauvais

1,886
1
12
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I completely agree with you however, this static function is part of a legacy code and initializes at the time of server startup. addtionally, we are not using applicationContext.getBean(User.class) explicitly anywhere in our code – Mukesh Kumar Sep 18 '17 at 07:53
Well if you want to inject dependancy the targeted object must pass through Spring's applicationContext somehow. getBean witth a prototype scope is a workaround to make Spring instantiate your User. However if Spring doesn't suit your needs for that scenario it's better to find a simple solution without than one turning everything upside down to make it works. – Baptiste Beauvais Sep 18 '17 at 08:31
As per my research, I don't have to mention '@Service' on 'User.java' because Spring will take care of this automatically if i mention ' – Mukesh Kumar Sep 19 '17 at 06:37

score 0 · Answer 3 · answered Sep 18 '17 at 08:00

0

By default, the name of the dispatcher servlet is xxx-servlet.xml where xxx is the servlet name. Which means that the spring is looking for dispatcher-servlet.xml, which is not the name of your XML config.

Thus the context itself is not loaded for you. Change it and test.

Apart from that, make sure that you follow best practises. Autowire on interfaces rather than on concrete class. Quick link for you - Spring: Why do we autowire the interface and not the implemented class?

answered Sep 18 '17 at 08:00

Karthik R

5,523
2
18
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Servlet-Dispatcher.xml is already there. I have mentioned in question too(first block). Pls check. and also please explain which part you want to change. – Mukesh Kumar Sep 18 '17 at 09:10
Did you read the answer carefully? The name of the xml should be dispatcher-servlet.xml not servlet-dispatcher.xml? – Karthik R Sep 18 '17 at 09:13
Sorry. there was typo mistake. It's dispatcher-servlet.xml only. updated the question. – Mukesh Kumar Sep 18 '17 at 09:19
If that's how your code is, no other clue. `@Autowired private IUserMilesHelper userHelper;` instead of Concrete class. That's the max I got here as of now. – Karthik R Sep 18 '17 at 09:22

score 0 · Answer 4 · answered Sep 18 '17 at 09:28

0

pleae change <context:component-scan base-package="com.eos.accounts" /> to <context:component-scan base-package="com.eos.accounts.*" />

give it a try and let me know the result. hope it helps.

answered Sep 18 '17 at 09:28

ali4j

522
3
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unfortunately I did not. :( I guess, Spring takes care of it. com.eos.accounts is equal com.eos.accounts.* – Mukesh Kumar Sep 18 '17 at 09:46
what's the point of this line `50` in web.xml? – ali4j Sep 18 '17 at 09:58
it's just a seq number. Let me know if you able to get the issue – Mukesh Kumar Sep 19 '17 at 06:43
check this post https://stackoverflow.com/questions/809775/what-does-the-servlet-load-on-startup-value-signify and make sure you're doing fine which `load-on-startup` tag dude – ali4j Sep 19 '17 at 07:24
Correct. i'm aware of `load-on-startup` I reckon, it has nothing to do with problem. – Mukesh Kumar Sep 19 '17 at 09:02

Spring Autowiring is not happening ? Object is not initializing at all

4 Answers4