Develop Reference

Autowired property is null in EnvironmentPostProcessor implementation class on startup

In my SpringBoot app, I have Autowired an configObject in the class that implements EnvironmentPostProcessor.
The injected class reads data from a different source on startup as this is required for the app to work.
But upon starting the application, the configObject is coming off as Null.
#SpringBootApplication
#EnableEncryptableProperties
#EnableConfigurationProperties
#EnableCaching
#Slf4j
public class SBApplication {
public static void main(String[] args) {
SpringApplication.run(SBApplication.class, args);
}
}
And the AppEnvironmentPostProcessor class where the Autowired object is called. This class is configured as org.springframework.boot.env.EnvironmentPostProcessor in spring.factories. The class gets called on start up.
#Slf4j
public class AppEnvironmentPostProcessor implements
EnvironmentPostProcessor, Ordered {
#Autowired
KeysConfig keysConfig;
#Override
public void postProcessEnvironment(ConfigurableEnvironment environment,
SpringApplication application) {
// keysConfig is null
String key = keysConfig.getSecretKeyMap().get("key12");
}
}
And in the KeysConfig class
#Component
public final class KeysConfig {
public Map getSecretKeyMap() {
//Returns key map
}
}
I am using Intellij Ultimate. How can I debug and resolve this?

EnvironmentPostProcessors are created before the application context has been created and, therefore, before dependency injection is possible. This means that #Autowired won’t work.
You’ll have to update your implementation to create an instance of KeysConfig itself, or to use a different approach that mimics whatever KeysConfig currently does.

Spring boot dependency injection of an interface

I have 2 spring boot microservice let's say core and persistence. where persistence has a dependency on core.
I have defined an interface in core whose implementation is inside persistence as below:
core
package com.mine.service;
public interface MyDaoService {
}
Persistence
package com.mine.service.impl;
#Service
public class MyDaoServiceImpl implements MyDaoService {
}
I am trying to inject MyDaoService in another service which is in core only:
core
package com.mine.service;
#Service
public class MyService {
private final MyDaoService myDaoService;
public MyService(MyDaoService myDaoService) {
this.myDaoService = myDaoService;
}
}
while doing this i am getting this weird error:
***************************
APPLICATION FAILED TO START
***************************
Description:
Parameter 0 of constructor in com.mine.service.MyService required a bean of type 'com.mine.service.MyDaoService' that could not be found.
Action:
Consider defining a bean of type 'com.mine.service.MyDaoService' in your configuration.
can anyone explain me why ?
NOTE: i have already included com.mine.service in componentscan of springbootapplication as below
package com.mine.restpi;
#SpringBootApplication
#EnableScheduling
#ComponentScan(basePackages = "com.mine")
public class MyRestApiApplication {
public static void main(String[] args) {
SpringApplication.run(MyRestApiApplication.class, args);
}
}

Try adding the #Service annotation to your impl classes and the #Autowired annotation to the constructor.
// Include the #Service annotation
#Service
public class MyServiceImpl implements MyService {
}
// Include the #Service annotation and #Autowired annotation on the constructor
#Service
public class MyDaoServiceImpl implements MyDaoService {
private final MyService myService ;
#Autowired
public MyDaoServiceImpl(MyService myService){
this.myService = myService;
}
}

As stated in the error message hint: Consider defining a bean of type 'com.mine.service.MyDaoService' in your configuration to solve this problem you can define in your package com.mine a configuration class named MyConfiguration annotated with #Configuration including a bean named myDaoService like below:
#Configuration
public class MyConfiguration {
#Bean
public MyDaoService myDaoService() {
return new MyDaoServiceImpl();
}
}

Try the following, move MyRestApiApplication class to com.mine package and remove #ComponentScan annotation.
package com.mine;
#SpringBootApplication
#EnableScheduling
public class MyRestApiApplication {
public static void main(String[] args) {
SpringApplication.run(MyRestApiApplication.class, args);
}
}

SpringBoot application doesn't autowire field

I do have ServiceImpl which looks like this:
#Service
#RequiredArgsConstructor
public class ServiceAImpl implements ServiceA {
private final String fieldA;
#Override
public boolean isFieldA(String text){
return fieldA.equals(text);
}
And I would like to inject a field value to fieldA in an Application.java from application.yml like this:
#EnableSwagger2
#SpringBootApplication
public class Application {
#Value("${fieldA}")
private String fieldA;
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public ServiceA serviceA() {
return new ServiceAImpl(fieldA);
}
But I receive the following error when running SpringBoot app:
Error creating bean with name 'serviceAImpl' defined in URLNo qualifying bean of type 'java.lang.String' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
Do you have any solution for that?

You annotated your class with #Service and defined it manually as a bean with the #Bean annotation. I do think the second is the way you planned to use it.
The #Service annotation will make this class get picked up by Spring's component scan and additionally create an instance of it.
Of course it tries to resolve the parameters and fails when it tries to find a matching "bean" for the String field because there is no simple String bean (and should not :) ).
Remove the #Service annotation and everything should work as expected.

Try this
#Service
public class ServiceAImpl implements ServiceA {
private final String fieldA;
#Autowire
public ServiceAImpl(#Value("${fieldA}") String fieldA){
this.fieldA = fieldA;
}
#Override
public boolean isFieldA(String text){
return fieldA.equals(text);
}
}
and this
#EnableSwagger2
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
You should not use #Service and #Bean for the same class!

Spring is not so smart :)
You should annotate your bean like:
#RequiredArgsConstructor
public class ServiceAImpl {
#Value("${fieldA}")
private final String something;
...
But I'm not sure it will work with the #RequiredFieldsConstructor, it would be simpler for you write down the constructor annotated with #Autowired and using the #Value annotation for the String parameter:
#Autowired
public ServiceAImpl(#Value("${aProp}") String string) {

You're using two bean declaration mechanisms:
You're registering your bean using #Service
You're registering a bean using #Bean
This means that your service will be created twice. The one defined using #Bean works properly, since it uses the #Value annotation to inject the proper value in your service.
However, the service created due to #Service doesn't know about the #Value annotation and will try to find any bean of type String, which it can't find, and thus it will throw the exception you're seeing.
Now, the solution is to pick either one of these. If you want to keep the #Bean configuration, you should remove the #Service annotation from ServiceAImpl and that will do the trick.
Alternatively, if you want to keep the #Service annotation, you should remove the #Bean declaration, and you should write your own constructor rather than relying on Lombok because this allows you to use the #Value annotation within the constructor:
#Service
public class ServiceAImpl implements ServiceA {
private final String fieldA;
/**
* This constructor works as well
*/
public ServiceAImpl(#Value("${fieldA}") String fieldA) {
this.fieldA = fieldA;
}
#Override
public boolean isFieldA(String text){
return fieldA.equals(text);
}
}

If you want to declare ServiceAImpl as a Spring bean in your Java Configuration file, you should remove the #Service annotation from the class declaration. These annotations doesn't work well together.
ServiceAImpl.java
import org.springframework.beans.factory.annotation.Autowired;
public class ServiceAImpl implements ServiceA {
private final String fieldA;
#Autowired
public ServiceAImpl(String fieldA) {
this.fieldA = fieldA;
}
#Override
public boolean isFieldA(String text) {
return fieldA.equals(text);
}
}
Application.java
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
#SpringBootApplication
public class Application {
#Value("${fieldA}")
private String fieldA;
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public ServiceA serviceA() {
return new ServiceAImpl(fieldA);
}
}
Your application.properties
fieldA=value

The below implementation works well for me. You have two issues, first you have to choose between #Service and #Bean and the other issue I've seen in your code was the #Value annotation, you have to use only to inject a value from the properties.
#SpringBootApplication
public class TestedValueApplication {
#Autowired
void printServiceInstance(ServiceA service) {
System.out.println("Service instance: " + service);
System.out.println("value==value? " + service.isFieldA("value"));
}
public static void main(String[] args) {
SpringApplication.run(TestedValueApplication.class, args);
}
#Bean
public ServiceA serviceA(#Value("${fieldA}") String fieldA) {
return new ServiceAImpl(fieldA);
}
}
Service:
public class ServiceAImpl implements ServiceA {
private String fieldA;
ServiceAImpl(String fieldA) {
this.fieldA = fieldA;
}
public boolean isFieldA(String text) {
return fieldA.equals(text);
}
}
application.properties:
fieldA=value

NullPointerException: Junit Spring annotation configuration

I am learning Spring framework and using this reference,
I have a UkranianSongs class
import javax.annotation.Nonnull;
public class UkrainianSongs implements CompactDisk{
#Override
#Nonnull
public String getTitle(){
return "Ukranian Songs";
}
#Override
#Nonnull
public String getArtist(){
return "Skriabin";
}
}
I am creating a bean in CDPlayerConfig class
#Configuration
#ComponentScan
public class CDPlayerConfig {
#Bean
public CompactDisk anUkranianDisk(){
return new UkrainianSongs();
}
}
And I am autowiring compact disk class in another class
#Component
public class CompactDiskBox {
#Autowired
public CompactDisk anUkrainianDisk;
}
I wrote a JUnit test where I am trying to assert anUkranianDisk bean was initialized correctly and is not null
#RunWith(JUnit4.class)
#ContextConfiguration(classes = CDPlayerConfig.class)
public class CompactDiskBoxTest {
#Autowired(required = true)
public CompactDiskBox compactDiskBox;
#Test
public void testUkranianDisk(){
assertNotNull(compactDiskBox.anUkrainianDisk);
}
}
This throws a NullPointerException as compactDiskBox is null which means it couldn't initialize the bean right. Am I missing something here?

In order to be able to use dependency injection in your unit/integration tests, you have to set up the Spring TestContext Framework. In order to do this you should run your tests with SpringJUnit4ClassRunner.class or SpringRunner.class. SpringRunner.class is just an alias for SpringJUnit4ClassRunner.class.

Annotate a POJO as Component

May I annotate a simple pojo by #Component ?
It is because IntelliJ says :
could not autowire, no beans found
Thanks

Of course you can annotate pojo with #Component, and then you can autowire it within another pojo also annotated with #Component e.g:
#Component
public class Computer {
#Autowired
Procesor procesor;
public void printName() {
System.out.println("486DX");
}
}
#Component
public class Procesor {
}
#SpringBootApplication
public class SpringOneApplication {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(SpringOneApplication.class, args);
Computer computer = (Computer) context.getBean("computer");
computer.printName();
}
}