On the analysis of the code snippet given, the null pointer exception occurred since your code doesn't ask the spring dependency injector to inject EmployerService as a dependency to EmployerController, so it doesn't inject the EmployerService bean class to the reference private EmployerService employerService; thus it is null in EmployerController. You can ask Spring Dependency Injector to inject dependency by adding @Autowire annotation private EmployerService service; refence in EmployerController

Update your EmployerService to the following will work

package io.javabrains;

import java.util.List;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import io.javabrains.Entity.Employer;

@RestController
public class EmployerController {

  //UPDATE : Autowiring
  @Autowired
  private EmployerService employerService;


  @RequestMapping("/employer")
  public List < Employer > getAllEmployers() {
    return service.getAllEmployers();
  }
  /*
   * @RequestMapping("/employer/{id}") public Employer getEmployer(@PathVariable
   * int id) { return employerService.getEmployer(id); }
   */

  @RequestMapping(method = RequestMethod.POST, value = "/employer/create")
  public void addEmployer(@RequestBody Employer employer) {
    employerService.addEmployer(employer);
  }
}

And Also, the same issue would occur in Service when trying to access repository.

Update EmployeeService.java code include @autorwired logic:

package io.javabrains;

import java.util.ArrayList;
import java.util.List;

import org.springframework.stereotype.Service;
import org.springframework.beans.factory.annotation.Autowired;

import io.javabrains.Entity.Employer;

@Service
public class EmployerService {

    @Autowired
    private Repository repository;

    public List<Employer>getAllEmployers(){
        List<Employer>employers = new ArrayList<>();
        repository.findAll()
        .forEach(employers::add);
        return employers;

    }

    public void addEmployer(Employer employer) {
        repository.save(employer);
    }    
}

The repository is not injected. In LoginController either create a constructor with your repositories (preferable way) or mark fields as @Autowired.

It would be good to have a separate class which implements ApplicationContextAware to provide application context to required classes. The problem here appears to be Spean bean life cycle and servlet container life cycle performing different operations.

i.e init can be called before context could be set by spring.

Please check/debug if you get non-null result for this - ShoppingCart shoppingCart = user.getShoppingCart();

Seems like the shoppingCart is null and it's not Spring specific issue.

which version of spring boot do you use? If you're using old version of spring, then you need to create the constructor and add @Autowired above the constructor instead of using lombok annotation. Or you can change the lombok annotations like @AllArgsConstructor(onConstructor_ = @Autowired). Or just remove the lombok annoation and add @Autowired above userService.

Also make sure userService is a Spring Bean, check the annotation in UserService, it should have @Service or @Component or if it's created by @Bean method.

It is clearly due to the fact your

postRepository is not autowired. Spring cannot intantiate it by itself until you specify it with an annotation @Autowired, or personally instantiate it say in a @PostConstruct way.

Have a new Interface

public interface PostRepository extends JpaRepository<Post , Long>{

}

And in your sevice class.

@AutoWired
private PostRepository postRepository;

Have your packages like this. All packages should be within the directory of SpringBootApp package.

Hope this helps !!

A - How To Read Custom Property From application.properties In Spring Boot

A-1) Application Properties file

On of the default location of application.properties file is src/main/resources. Create this folder and also this file. Assuming your scenario, put the following properties inside application.properties file;

myconfig.ip=192.168.166.42
myconfig.port=8090

A-2) Configuration Class : AppConfig

In order to read the properties file, you need a class with @Configuration annotation. You need appropriate fields with @Value annotation for all the properties that you need to read. In addition, also you need the getter methods for these fields marked with @Value annotation. Please note that naming this class as "Configuration" is a very bad choice because there is also an annotation with the same name, thus I name it as "AppConfig"

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;

@Configuration
public class AppConfig {

    @Value("${myconfig.ip}")
    private String ip;

    @Value("${myconfig.port}")
    private int port;

    public String getIp() {
        return ip;
    }

    public int getPort() {
        return port;
    }

}

A-3) Demo

Then you create a fields of this AppConfig class which is written above, and mark it with @Autowired annotation. Then you can read the properties files easily;

@RestController
@RequestMapping("/")
public class InputManagementController {

    @Autowired
    private AppConfig config;

    @RequestMapping("/test")
    public String test() {
        return String.format(
                "Configuration Parameters: Port: %s, Ip: %s", 
                config.getPort(),
                config.getIp()
        );
    }

}

A-4) Output

B - Solution To Problem

B-1) InputManagementController.java

@RestController
public class InputManagementController {

    @Autowired
    private AppConfig configuration;

    @Autowired
    private ElasticSearchInterface elasticSearchInterface;

    @GetMapping("/crawler/start")
    public String start() {
        try {

            System.out.println(configuration.getIp());
            es.getInputs();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "started";
    }
}

B-2) ElasticSearchInterface.java

@Component
public class ElasticSearchInterface {

    @Autowired
    private AppConfig configuration;

    public List<Map<String, Object>> getInputs() {
        System.out.println(configuration.getIp());

        return null;
    }

}

B-3) AppConfig.java

@Configuration
public class AppConfig {

    @Value("${myconfig.ip}")
    private String ip;

    @Value("${myconfig.port}")
    private int port;

    public String getIp() {
        return ip;
    }

    public int getPort() {
        return port;
    }

}

@Autowired
private AlertRepository alertRepository;

and On your main application class add @EnableAutoConfiguration

@SpringBootApplication
@EnableAutoConfiguration
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Also if you are not using @Repository then spring will never create bean for your repo, In that case it will throw nullPointer exception

  @Repository 
    public interface AlertRepository extends
     JpaRepository<Alert, Integer>{  }

You are most likely running on JDK 11 or higher. One of the libraries you use is javassist (probably as a dependency of the Spring framework). Version 3.22 is not compatible with JDK 11 and causes the error.

Either upgrade to javassist 3.24 (by upgrading to the newest Spring Boot version 2.2.4.RELEASE which has a dependency to it) or downgrade to JDK 8.

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.3.RELEASE</version>
    </parent>

As a tip for investigating Java error logs:

1. Locate the first error. In your case it's: 2019-04-02 22:27:38.143 ERROR 13892 --- [ restartedMain] o.s.boot.SpringApplication : Application run failed

2. Follow the associated stack trace and go to the innermost exception, i.e.go the last Caused by: before the next error starts. In your case it's:

Caused by: java.lang.NullPointerException: null
    at javassist.util.proxy.SecurityActions.setAccessible(SecurityActions.java:103) ~[javassist-3.22.0-GA.jar:na]
    at javassist.util.proxy.DefineClassHelper.toClass3(DefineClassHelper.java:151) ~[javassist-3.22.0-GA.jar:na]

That's the real cause that you want to investigate.

The problem is not related neither with Controller nor Service classes.

A not-null Authentication instance is successfully injected into the controller. Otherwise a NullPointerException would be thrown in the userService.getLoggedinUser(...) method at the moment it does auth.getName().

UserMapper might return null in two cases:

• The Authentication.getName()'s method call returns null
  • Why? If UserMapper.getUser(...) receives a null username as argument, the query will try to match using that null. Then, unless one user has null as username, the UserMapper will return null since the database returns an empty ResulSet.
• There's no user in database that matches the given username.

I hope it might help!

You're running your tests with a runner that's not Spring-aware, so no wiring is happening. Look at the Spring Boot testing documentation, all their examples use @RunWith(SpringRunner.class). To mock a bean, annotate it with @MockBean, not @Mock. Make sure that the spring-boot-starter-test is included in your POM.

The @Autowired annotation will not create your decryptor object, but will try to locate a Bean of that type and inject it in your DecryptionService. This means that you should not use a constructor to instantiate your DecryptionService. The DecryptionService should be defined as a @Service and injected in another component (@Component, @Controller etc.), from where you will invoke the specific methods for decrypting your data.

The problem is that in your method under test you call:

myComponent1.andThen(myComponent2)

As myComponent1 is a mock and you haven't stubbed andThen method call, the expression evaluates to null, which you pass to forEach.

Fix 1:

• create a new mock of Consumer.class. Let's call it combinedConsumer
• stub myComponent1.andThen to return combinedConsumer

Fix 2:

• Instruct Mockito to call real method for andThen

Mockito.when(consumer1.andThen(consumer2)).thenCallRealMethod();

More general remarks:

• You don't need a @SpringBootTest for a single service test. I would opt for MockitoExtension / Runner. Your test will be less fragile and faster, as currently entire spring app context needs to be created.
• doNothing is the default action for a void method (in your case Consumer.accept). You don't need to stub it.
• Mockito is enough for this test (nothing PopwerMockito-specific is used)