考虑在配置中定义一个“javax.persistence.EntityManager”类型的bean

Question

我是spring的初学者。所以现在我开始学习spring boot并构建这个简单的项目，但是当我运行它时，我得到了这样的错误“Field entityManager in sagala.rest.boot.remade.dao.EmployeeDaoImpl required a bean of type'javax.persistence.entityManager'that count found”。

这是我的控制器类

package sagala.rest.boot.remade.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import sagala.rest.boot.remade.entity.Employee;
import sagala.rest.boot.remade.service.EmployeeService;


@RestController
@RequestMapping("/api")
public class MainController {

@Autowired
private EmployeeService employeeService;

@GetMapping("/employees")
public List<Employee> findAll() {
    return employeeService.findAll();
}

}

这是服务类

package sagala.rest.boot.remade.service;

import java.util.List;

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

import sagala.rest.boot.remade.dao.EmployeeDao;
import sagala.rest.boot.remade.entity.Employee;

@Service
public class EmployeeServiceImpl implements EmployeeService {

@Autowired
private EmployeeDao employeeDao;

@Override
@Transactional
public List<Employee> findAll() {

    return employeeDao.findAll();
}

}

下面是DAO类

package sagala.rest.boot.remade.dao;

import java.util.List;

import javax.persistence.EntityManager;

import org.hibernate.Session;
import org.hibernate.query.Query;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;

import sagala.rest.boot.remade.entity.Employee;

@Repository
public class EmployeeDaoImpl implements EmployeeDao {

@Autowired
private EntityManager entityManager;

@Override
public List<Employee> findAll() {
    Session session =entityManager.unwrap(Session.class);
    Query<Employee> query =session.createQuery("from Employee", Employee.class);
    List<Employee> employees =query.getResultList();
    return employees;
}

}

下面是实体类

package sagala.rest.boot.remade.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="employee")
public class Employee {

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id")
private int id;

@Column(name="first_name")
private String firstName;

@Column(name="last_name")
private String lastName;

@Column(name="email")
private String email;

public Employee() {

}

public Employee(String firstName, String lastName, String email) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.email = email;
}

public int getId() {
    return id;
}

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

public String getFirstName() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName = firstName;
}

public String getLastName() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName = lastName;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}

}

这是POM文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.2.6.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>sagala</groupId>
<artifactId>rest.boot.remade</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>rest.boot.remade</name>
<description>Demo project for Spring Boot</description>

<properties>
    <java.version>1.8</java.version>
    <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <scope>runtime</scope>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

</project>

以下是应用程序属性

spring.datasource.url=jdbc:mysql:/localhost:3306/employee_directory？usessl=false&servertimezone=utc spring.datasource.username=spring********spring.datasource.password=spring*********

如果有人能帮我。谢谢

Answer 1

我把spring boot版本从2.2.6改成2.1.13，一切正常。在较新的spring boot版本中，javax.persistence.EntityManager似乎已经损坏。尽管多次删除repo，但当我试图将JpaRepository接口扩展为另一个替代dao实现时，仍然找不到它。