spring boot jpa - 使用封装好的方法对数据库进行增删改查

依赖:

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
</dependency>

配置application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=password
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
# 若启动时发现数据库没有此表则创建表
spring.jpa.hibernate.ddl-auto=update
# 控制台显示执行的sql语句
spring.jpa.show-sql=true

项目所需配置结构

User.java 实体类

package com.laoxu.springboot.entity;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Data;

import javax.persistence.*;

@JsonIgnoreProperties(value = {"hibernateLazyInitializer", "handler"})
@Data
@Entity
@Table(name = "tb_user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "name", length = 50)
    private String name;
    @Column
    private String email;

}

UserRepository.java 为jpa操作类

package com.laoxu.springboot.repository;

import com.laoxu.springboot.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Integer> {

}

编写控制器，实现对数据库的操作

package com.laoxu.springboot.controller;

import com.laoxu.springboot.entity.User;
import com.laoxu.springboot.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class UserController {
    @Autowired
    private UserRepository userRepository;

    @RequestMapping("/user/{id}")
    @ResponseBody
    public User getUser(@PathVariable("id") Integer id){
        User user = userRepository.getOne(id);
        return user;
    }
    @GetMapping("/user")
    @ResponseBody
    public User insertUser(User user){
        User save = userRepository.save(user);
        return save;
    }


}

自定义查询

Spring Data JPA 可以根据接⼝⽅法名来实现数据库操作，主要的语法是 findXXBy、readAXXBy、 queryXXBy、countXXBy、getXXBy 后⾯跟属性名称，利⽤这个功能仅需要在定义的 Repository 中添加对应 的⽅法名即可，使⽤时 Spring Boot 会⾃动帮我们实现

简单demo

https://github.com/1051513344/spring-boot-jpa-demo

例子：

自定义查询

package com.neo.repository;

import com.neo.model.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;

import javax.transaction.Transactional;
import java.util.List;

@Repository
public interface UserRepository extends JpaRepository<User, Long> {


   List<User> findAllByIdLessThan(Long maxId);

   @Query(value="select * from `user` where id < 50", nativeQuery=true)
   List<User> getAllUserByMaxId();

   @Query(value = "update `user` set user_name='张老三' where id = ?1", nativeQuery = true)
   @Modifying
   @Transactional
   void updateUserNameById(Long id);


}

service层调用

package com.neo.service;

import com.neo.model.User;
import com.neo.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.*;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserRepository userRepository;

    @Override
    public List<User> getAllUser() {
        //查询所有数据
        return userRepository.findAll();
    }

    @Override
    public User getUserByExample() {
        //根据条件查询
        User user = new User();
        user.setId(1L);
        Example<User> example = Example.of(user);
        return userRepository.findOne(example).get();
    }

    @Override
    public List<User> getAllUserByPage() {
        //分页+排序查询演示：
        //Pageable pageable = new PageRequest(page, size);//2.0版本后,该方法以过时
        Sort sort = new Sort(Sort.Direction.DESC, "id");
        Pageable pageable = PageRequest.of(0, 5, sort);
        Page<User> users = userRepository.findAll(pageable);
        return users.getContent();
    }

    @Override
    public List<User> getUserByLessId(Long maxId) {
        return userRepository.findAllByIdLessThan(maxId);
    }

    @Override
    public List<User> getUserByMaxId() {
        return userRepository.getAllUserByMaxId();
    }


    @Override
    public void updateUserNameById(Long id) {
        userRepository.updateUserNameById(id);
    }

    @Override
    public User getUserById(Long id) {
        return userRepository.findById(id).get();
    }
}