How to use entitymanager with Micronaut?

问题

I'm new in Micronaut framework and I'm trying to use entitymanager to create my repository. I created my repository like this

public interface EmployeeRepository {
    Employee save(@NotNull Employee employee);
    Employee update(@NotNull Employee employee);
    List<Employee> findAll();
    Optional<Employee> findById(@NotNull Long id);
}

and I used this class to implement the interface and to inject entitymanager

@Singleton
public class EmployeeRepositoryImpl implements EmployeeRepository{
    @PersistenceContext
    private EntityManager entityManager;

    public EmployeeRepositoryImpl(@CurrentSession EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    @Override
    @Transactional
    public Employee save(@NotNull Employee employee) {
        entityManager.persist(employee);
        return employee;
    }

    @Override
    @Transactional
    public Employee update(@NotNull Employee employee) {
        return entityManager.merge(employee);
    }

    @Override
    @Transactional(readOnly = true)
    public List<Employee> findAll() {
        String qlString = "SELECT * FROM Employee";
        TypedQuery<Employee> query = entityManager.createQuery(qlString, Employee.class);
        return query.getResultList();
    }

    @Override
    @Transactional(readOnly = true)
    public Optional<Employee> findById(@NotNull Long id) {
        return Optional.ofNullable(entityManager.find(Employee.class, id));
    }
}

The problem is that I have always this error :

Message: No bean of type [javax.persistence.EntityManager] exists. Ensure the class is declared a bean and if you are using Java or Kotlin make sure you have enabled annotation processing.
Path Taken: new $EmployeeControllerDefinition$Intercepted([EmployeeRepositoryImpl employeeRepository],BeanContext beanContext,Interceptor[] interceptors) --> new $EmployeeRepositoryImplDefinition$Intercepted([EntityManager entityManager],BeanContext beanContext,Interceptor[] interceptors)
io.micronaut.context.exceptions.DependencyInjectionException: Failed to inject value for parameter [entityManager] of class: com.milamed.dao.$EmployeeRepositoryImplDefinition$Intercepted

PS: I have enabled the annotation processing

回答1:

You haven't provided enough about your project to know for sure what is missing but I have created a working example for you at https://github.com/jeffbrown/mohamedmiledijpa.

https://github.com/jeffbrown/mohamedmiledijpa/blob/master/src/main/java/mohamedmiledijpa/Employee.java

package mohamedmiledijpa;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Employee {

    @Id
    @GeneratedValue
    private Long id;

    private String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }
}

https://github.com/jeffbrown/mohamedmiledijpa/blob/master/src/main/java/mohamedmiledijpa/EmployeeRepository.java

package mohamedmiledijpa;

import javax.validation.constraints.NotNull;
import java.util.List;
import java.util.Optional;

public interface EmployeeRepository {
    Employee save(@NotNull Employee employee);
    Employee update(@NotNull Employee employee);
    List<Employee> findAll();
    Optional<Employee> findById(@NotNull Long id);
}

https://github.com/jeffbrown/mohamedmiledijpa/blob/master/src/main/java/mohamedmiledijpa/EmployeeRepositoryImpl.java

package mohamedmiledijpa;

import io.micronaut.configuration.hibernate.jpa.scope.CurrentSession;
import io.micronaut.spring.tx.annotation.Transactional;

import javax.inject.Singleton;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.TypedQuery;
import javax.validation.constraints.NotNull;
import java.util.List;
import java.util.Optional;

@Singleton
public class EmployeeRepositoryImpl implements EmployeeRepository{
    @PersistenceContext
    private EntityManager entityManager;

    public EmployeeRepositoryImpl(@CurrentSession EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    @Override
    @Transactional
    public Employee save(@NotNull Employee employee) {
        entityManager.persist(employee);
        return employee;
    }

    @Override
    @Transactional
    public Employee update(@NotNull Employee employee) {
        return entityManager.merge(employee);
    }

    @Override
    @Transactional(readOnly = true)
    public List<Employee> findAll() {
        String qlString = "SELECT e FROM Employee e";
        TypedQuery<Employee> query = entityManager.createQuery(qlString, Employee.class);
        return query.getResultList();
    }

    @Override
    @Transactional(readOnly = true)
    public Optional<Employee> findById(@NotNull Long id) {
        return Optional.ofNullable(entityManager.find(Employee.class, id));
    }
}

https://github.com/jeffbrown/mohamedmiledijpa/blob/master/src/main/java/mohamedmiledijpa/EmployeeController.java

package mohamedmiledijpa;

import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.annotation.Post;

import java.util.List;

@Controller("/employee")
public class EmployeeController {

    private EmployeeRepository employeeRepository;

    public EmployeeController(EmployeeRepository employeeRepository) {
        this.employeeRepository = employeeRepository;
    }

    @Get("/")
    public List<Employee> list() {
        return employeeRepository.findAll();
    }

    @Post("/")
    public Employee create(@Body Employee employee) {
        return employeeRepository.save(employee);
    }
}

https://github.com/jeffbrown/mohamedmiledijpa/blob/f6500d3fb24190ed59ca64dcc28a02f8069fedfd/build.gradle#L29

compile "io.micronaut.configuration:micronaut-hibernate-jpa"

That all appears to work:

~ $ curl http://localhost:8080/employee
[]
~ $ 
~ $ curl -d '{"name":"Jake"}' -H "Content-Type: application/json" -X POST  http://localhost:8080/employee
{"id":1,"name":"Jake"}
~ $ 
~ $ curl -d '{"name":"Zack"}' -H "Content-Type: application/json" -X POST  http://localhost:8080/employee
{"id":2,"name":"Zack"}
~ $ 
~ $ curl http://localhost:8080/employee
[{"id":1,"name":"Jake"},{"id":2,"name":"Zack"}]

来源：https://stackoverflow.com/questions/55000143/how-to-use-entitymanager-with-micronaut