使用 Spring boot 整合JPA 实现数据的持久化

本文将介绍 spring boot 整合 JPA 来实现数据的持久化。

一、添加依赖 

  • 修改pom,引入依赖
<!-- 引入jpa 依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

  • 修改 application.properties,配置相关信息

    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.url=jdbc:mysql://localhost:3306/test
    spring.datasource.username=root
    spring.datasource.password=root
    spring.jpa.hibernate.ddl-auto=update
    spring.jpa.show-sql=true
    spring.jackson.serialization.indent_output=true
    
  • 创建实体类 package com.study.entity;

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

@Entity
@Table(name="t_user")
public class User {

    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    private String userName;
    private String password;

    public Integer getId() {
        return id;
    }

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

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}
  • 创建repository接口并继承 CrudRepository

    package com.study.repository;
    
    import org.springframework.data.jpa.repository.Query;
    
    import org.springframework.data.repository.CrudRepository;
    
    import org.springframework.data.repository.query.Param;
    
    import com.study.entity.User;
    
    /**
    
    - 注意:
    - 1.这里这里是interface,不是class
    - 
    - 2.CrudRepository里面的泛型,第一个是实体类,第二个是主键的类型
    - 
    - 3.由于crudRepository 里面已经有一些接口了,如deleteAll,findOne等, 我们直接调用即可
    - 
    - 4.当然,我们也可以根据自己的情况来实现自己的接口,如下面的getUser()方法,jpql语句和hql语句差不多
    - 
    - */
      public interface UserRepository extends CrudRepository<User, Integer> {
       /**
      - 我们这里只需要写接口,不需要写实现,spring boot会帮忙自动实现
      - 
      - */
       @Query("from User where id =:id ")
       public User getUser(@Param("id") Integer id);
      }
    
    
  • 创建service 接口

package com.study.service;

import com.study.entity.User;

public interface UserService {

    public User getUser(Integer id);

} 实现 package com.study.service.impl;

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

import org.springframework.stereotype.Service;

import com.study.entity.User;

import com.study.repository.UserRepository;

import com.study.service.UserService;

@Service
public class UserServiceImpl implements UserService {

	@Autowired
	UserRepository repository;
	@Override
	public User getUser(Integer id) {
        //有两种方式:
        //1.调用crudRepository的接口
        //return repository.findOne(id);
        //2.调用我们自己写的接口
        return repository.getUser(id);
    }
}

  • 创建controller
package com.study.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.study.entity.User;
import com.study.service.UserService;

@RestController
public class UserController {

    @Autowired

    UserService service;

    @RequestMapping("/users/{id}")
    public User getUser(@PathVariable("id") Integer id){

        return service.getUser(id);
    }
}
  • 测试,在浏览器中访问 http://localhost:8090/test/users/1

图片描述