How to get the instance of JpaRepository? [duplicate] - spring

Question

This question already has answers here:
Why is my Spring #Autowired field null?
(21 answers)
Closed 1 year ago.
I am new to Spring, this is maybe newbie question.
I create a Repository:
import org.springframework.data.jpa.repository.JpaRepository;
public interface TaskRepository extends JpaRepository<Task, String>{
}
The Repository work fine with my RestController
import org.springframework.web.bind.annotation.*;
#RestController
public class TaskController {
private final TaskRepository repository;
TaskController(TaskRepository repository) {
this.repository = repository;
}
// Aggregate root
// tag::get-aggregate-root[]
#GetMapping("/Tasks")
public List<Task> all() {
return repository.findAll();
}
// end::get-aggregate-root[]
#PostMapping("/Tasks")
public Task newTask(#RequestBody Task newTask) {
return repository.save(newTask);
}
// Single item
#GetMapping("/Tasks/{id}")
public Task one(#PathVariable String id) {
return repository.findById(id)
.orElseThrow(() -> new TaskNotFoundException(id));
}
#PutMapping("/Tasks/{id}")
public Task replaceTask(#RequestBody Task newTask, #PathVariable String id) {
return repository.findById(id)
.map(Task -> {
Task.setSparkAppId(newTask.getSparkAppId());
Task.setValue(newTask.getValue());
return repository.save(Task);
})
.orElseGet(() -> {
return repository.save(newTask);
});
}
#DeleteMapping("/Tasks/{id}")
public void deleteTask(#PathVariable String id) {
repository.deleteById(id);
}
}
However, I want to use that JpaRepository for my internal logic. I create a TaskHandler listener, that will update new Task in the database.
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.spark.launcher.SparkAppHandle;
import org.springframework.beans.factory.annotation.Autowired;
import java.util.Optional;
import java.util.List;
public class TaskListener implements SparkAppHandle.Listener {
#Autowired
private TaskRepository repository;
private static final Logger logger = LoggerFactory.getLogger(TaskListener.class);
public Task task;
public TaskListener(Task task) {
this.task = task;
}
#Override
public void stateChanged(SparkAppHandle handle) {
String curAppId = handle.getAppId();
SparkAppHandle.State curState = handle.getState();
String curStateStr = curState.toString();
logger.info("app id " + curAppId + " state " + curStateStr);
Optional<Throwable> opErr = handle.getError();
opErr.ifPresent(throwable -> logger.error(throwable.getMessage()));
this.task.setSparkAppId(curAppId);
this.task.setState(curStateStr);
//replaceTask(task, task.getTaskId());
}
#Override
public void infoChanged(SparkAppHandle handle) {
String curAppId = handle.getAppId();
SparkAppHandle.State curState = handle.getState();
String curStateStr = curState.toString();
logger.info("app id " + curAppId + " state " + curStateStr);
// SparkTaskModel.getInstance().executeUpdateTask(this.taskId, curAppId, curStateStr);
Optional<Throwable> opErr = handle.getError();
if (opErr.isPresent()){
logger.error(opErr.get().getMessage());
}
this.task.setSparkAppId(curAppId);
this.task.setState(curStateStr);
//replaceTask(task, task.getTaskId());
}
// not work because repository is null
public Task replaceTask(Task newTask, String id) {
return repository.findById(id)
.map(Task -> {
Task.setSparkAppId(newTask.getSparkAppId());
Task.setValue(newTask.getValue());
return repository.save(Task);
})
.orElseGet(() -> {
return repository.save(newTask);
});
}
}
I cannot put the Repository into Contructor because I create the TaskListener object in my program, and I don't know what to put in place of Repository should it in TaskListener contructor.
Error: (xxx was my project name censored...)
java.lang.NullPointerException
at xxx.xxx.xxx.xxx.spark_launcher_for_meow.xxx.tasksparklauncher.TaskListener.replaceTask(TaskListener.java:70)
at xxx.xxx.xxx.xxx.spark_launcher_for_meow.xxx.tasksparklauncher.TaskListener.stateChanged(TaskListener.java:47)
at org.apache.spark.launcher.AbstractAppHandle.fireEvent(AbstractAppHandle.java:160)
at org.apache.spark.launcher.AbstractAppHandle.setState(AbstractAppHandle.java:137)
at org.apache.spark.launcher.AbstractAppHandle.setState(AbstractAppHandle.java:124)
at org.apache.spark.launcher.LauncherServer$ServerConnection.handle(LauncherServer.java:315)
at org.apache.spark.launcher.LauncherConnection.run(LauncherConnection.java:58)
at java.base/java.lang.Thread.run(Thread.java:829)
The error point to:
repository.findById(id)....
in function
replaceTask
Said that repository is null.

Answer 1

#Autowired won't work since TaskListener is not a bean managed by Spring, but a bean that you instantiate manually.
You can simply pass TaskRepository as 2nd constructor argument
public class TaskListener implements SparkAppHandle.Listener {
private final TaskRepository repository;
public final Task task;
public TaskListener(TaskRepository repository, Task task) {
this.repository = repository;
this.task = task;
}
// other stuff
}
And then somewhere in your code your that instantiates TaskListener you autowire TaskRepository and use it as constructor parameter
#Service // << this means that bean is managed by Spring
// and all autowirings will be automatically done by Spring
// therefore taskRepository will be NOT null
public class SomeTaskListenerService {
#Autowired
private TaskRepository taskRepository;
public void someMethod() {
Task task = ... // obtain task
TaskListener listener = new TaskListener(taskRepository, task);
// do some actions with the listener
}
}

Answer 2

You can use multiple constructors in your TaskListener class. But in this case, you have to add #Autowired for the constructor where spring injection is required.
So your TaskListener class, you can modify like this.
private final TaskRepository repository;
public Task task;
public TaskListener(Task task) {
this.task = task;
}
#Autowired
TaskListener(TaskRepository repository) {
this.repository = repository;
}