In springboot autowired is not working, always null?

Question

In spring-boot application using springsecurity for writing custom autentication. CustomUserService is a interface and has a implementation class and a repository to fetch data from database.

@Component
    public class CustomAuthenticationProvider implements AuthenticationProvider{
    @Autowired
    private CustomUserService userService;

    @override
    someMethod(){//method of CustomUserService interface.
    userService.display();//here  "userService"  is always  null coming
    }
    }

kept @service on implementation & used @ComponentScan for basepackages discovery

Did you use any anotations for the CustomUserService implementation class — Sunimal S.K Malkakulage, Mar 01 '18 at 06:19
Put `@Service` or `@Component` on the class which implements `CustomUserService` interface and also don't forget to keep this implementing class in the radar of component scan. — Atul Dwivedi, Mar 01 '18 at 06:23
show you stacktrace, the full class `CustomAuthenticationProvider` and the main class — Patrick, Mar 01 '18 at 07:24
Removed some lines : java.lang.NullPointerException: null at com.example.demo.configs.CustomAuthenticationProvider.authenticate(CustomAuthenticationProvider.java:74) ~[classes/:na] at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:174) ~[spring-security-core-4.1.4.RELEASE.jar:4.1.4.RELEASE] at org.springframework.security.authentication.ProviderManager.authenticate(ProviderManager.java:199) ~[spring-security-core-4.1.4.RELEASE.jar:4.1.4.RELEASE] at — user2709752, Mar 01 '18 at 07:52
Can you show the code, where you use the CustomAuthenticationProvider class? Do you create an instance of that class by yourself with the new keyword? — dunni, Mar 01 '18 at 08:14
I followed this code javainsimpleway.com/spring-security-using-custom-authentication-provider/ — user2709752, Mar 01 '18 at 08:55
Possible duplicate of [Why is my Spring @Autowired field null?](https://stackoverflow.com/questions/19896870/why-is-my-spring-autowired-field-null) — dur, Mar 01 '18 at 14:30

score 0 · Answer 1 · answered Mar 01 '18 at 06:23

As long as there is only a single implementation of the interface and that implementation is annotated with @Component with Spring's component scan enabled, then Spring framework can find out the (interface, implementation) pair.

In this case, if it is null , then either the implementation class is not annotated with @Component or component scan is not working

score 0 · Answer 2 · answered Mar 01 '18 at 06:39

0

Check whether you annotate CustomUserService implementation class @Component or @Service and whether component scan can discover this service.

answered Mar 01 '18 at 06:39

Sunimal S.K Malkakulage

510
1
5
14

kept service annotation on implementation & ComponentScan annotation for basepackages discovery – user2709752 Mar 01 '18 at 06:49
I have a confusion in the provided code `@override someMethod(){//method of CustomUserService interface. userService.display();//here "userService" is always null coming }`. for method `someMethod()` you commented as `//method of CustomUserService interface`. but you used `@override` . still the class `CustomAuthenticationProvider` implements only `AuthenticationProvider`. – Sunimal S.K Malkakulage Mar 01 '18 at 07:30
I am using code in http://javainsimpleway.com/spring-security-using-custom-authentication-provider/ . In CustomAuthenticationProvider class, "userService" reference is always null – user2709752 Mar 01 '18 at 07:38
This also can be happen if you instantiate a object `CustomUserService` with `new` – Sunimal S.K Malkakulage Mar 01 '18 at 14:25

Ubercool · Answer 3 · 2018-03-03T12:58:55.553

In spring boot application, you don't have to explicitly enable component scan. All the annotated classes will automatically be registered as beans which are present under the package where the spring-boot application class (annotated with @SpringBootApplication) is present.

So if you Application class is present in com.abc package all the subpackages of com.abc will be scanned for spring beans. Refer the tree below:

+--- src
|   +--- main
|   |   +--- java
|   |   |   +--- com
|   |   |   |   +--- application
|   |   |   |   |   +--- Application.java
|   |   |   |   |   +--- beans
|   |   |   |   |   |   +--- ASpringBean.java
|   |   |   |   |   |   +--- AnotherSpringBean.java

May be in your case the beans are not getting discovered because they are outside application class package.

score 0 · Accepted Answer · answered Mar 04 '18 at 17:07

0

My bad!.......some where in the code I used new Keyword to create instance of CustomAuthenticationProvider, so that's why spring is not autowiring instances inside of CustomAuthenticationProvider class.

answered Mar 04 '18 at 17:07

user2709752

488
6
26

In springboot autowired is not working, always null?

4 Answers4