SpringDataJPA入门

第一步，引入pom

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.1.4.RELEASE</version>
  <relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
  </dependency>
  <!-- springBoot JPA的起步依赖 -->
  <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-data-jpa -->
  <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
  </dependency> 
  <!-- MySQL连接驱动 -->
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.35</version>
  </dependency>
</dependencies>

第二步，创建User的pojo

数据库

package com.hikktn.entity;
import javax.persistence.*;
import java.io.Serializable;
/**
 * @ClassName UserEntity
 * @Description TODO
 * @Author lisonglin
 * @Date 2021/4/2 15:41
 * @Version 1.0
 */
@Entity
@Table(name = "user", schema = "test")
public class UserEntity implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String username;
    private String password;
    @Id
    @Column(name = "id")
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    @Basic
    @Column(name = "username")
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    @Basic
    @Column(name = "password")
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        UserEntity that = (UserEntity) o;
        if (id != that.id) return false;
        if (username != null ? !username.equals(that.username) : that.username != null) return false;
        if (password != null ? !password.equals(that.password) : that.password != null) return false;
        return true;
    }
    @Override
    public int hashCode() {
        int result = id;
        result = 31 * result + (username != null ? username.hashCode() : 0);
        result = 31 * result + (password != null ? password.hashCode() : 0);
        return result;
    }
    @Override
    public String toString() {
        return "UserEntity{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + '}';
    }
}

第三步，实现接口

package com.hikktn.repository;
import com.hikktn.entity.UserEntity;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import java.util.List;
/**
* @ClassName UserRepository
* @Description TODO
* @Author lisonglin
* @Date 2021/4/2 16:00
* @Version 1.0
*/
public interface UserRepository extends JpaRepository<UserEntity, Integer>, JpaSpecificationExecutor<UserEntity> {
    // 查询全部
    List<UserEntity> findAll();
}

第四步，测试

package com.hikktn.test;
import com.hikktn.MySpringBootApplication;
import com.hikktn.entity.UserEntity;
import com.hikktn.repository.UserRepository;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
import java.util.Optional;
/**
 * @ClassName JpaTest
 * @Description TODO
 * @Author lisonglin
 * @Date 2021/4/2 16:02
 * @Version 1.0
 */
@RunWith(SpringRunner.class)
@SpringBootTest(classes= MySpringBootApplication.class)
public class JpaTest {
    @Autowired
    private UserRepository userRepository;
    @Test
    public void testGetUserAll(){
        List<UserEntity> users = userRepository.findAll();
        System.out.println(users);
    }
    @Test
    public void testAddUser(){
        UserEntity userEntity =new UserEntity();
        userEntity.setUsername("tom");
        userEntity.setPassword("123");
        userRepository.save(userEntity);
    }
    @Test
    public void testFindOneUser(){
        Optional<UserEntity> byId = userRepository.findById(1);
        System.out.println(byId.get());
    }
    @Test
    public void testDeleteUser() {
        userRepository.deleteById(5);
    }
    @Test
    @Transactional(rollbackFor = Exception.class)
//    @Rollback(value = false)//发生异常不回滚
    public void update(){
        Optional<UserEntity> optional = userRepository.findById(1);
        System.out.println(optional.orElseGet(UserEntity::new));
    }
}

第五步，增删改查

package com.hikktn.controller;
import com.hikktn.entity.UserEntity;
import com.hikktn.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.web.bind.annotation.*;
import java.util.Optional;
/**
 * @ClassName UserController
 * @Description TODO
 * @Author lisonglin
 * @Date 2021/4/2 22:01
 * @Version 1.0
 */
@RestController
@RequestMapping(path = "/user")
public class UserController {
    @Autowired
    private UserRepository userRepository;
    @GetMapping(path = "/all")
    @ResponseBody
    public Iterable<UserEntity> getAllUsers(){
        return userRepository.findAll();
    }
    /*
        增加用户
     */
    @PostMapping()
    public UserEntity saveUser(@RequestBody UserEntity user) {
        return userRepository.save(user);
    }
    /*
        删除用户
     */
    @DeleteMapping("/{id}")
    public void deleteUser(@PathVariable("id") int userId) {
        userRepository.deleteById(userId);
    }
    /*
        修改用户
     */
    @PutMapping("/{id}")
    public UserEntity updateUser(@PathVariable("id") int userId, @RequestBody UserEntity user) {
        user.setId(userId);
        return userRepository.saveAndFlush(user);
    }
    /*
        查询用户
     */
    @GetMapping("/{id}")
    public UserEntity getUserInfo(@PathVariable("id") int userId) {
        Optional<UserEntity> optional = userRepository.findById(userId);
        return optional.orElseGet(UserEntity::new);
    }
    /*
        分页查询多个用户
     */
    @GetMapping("/list")
    public Page<UserEntity> pageQuery(@RequestParam(value = "pageNum", defaultValue = "1") Integer pageNum,
                                      @RequestParam(value = "pageSize", defaultValue = "10") Integer pageSize) {
        return userRepository.findAll(PageRequest.of(pageNum - 1, pageSize));
    }
}