SpringBoot 学习之整合 SpringDataJPA
项目环境：Jdk11.0.2、MySql8.0.19
一、创建普通Java项目
二、修改 pom.xml 文件
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>org.examplegroupId>
<artifactId>springboot-jpaartifactId>
<version>1.0-SNAPSHOTversion>
<packaging>jarpackaging>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.2.6.RELEASEversion>
parent>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-webartifactId>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-data-jpaartifactId>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.19version>
dependency>
dependencies>
project>
三、创建SpringBoot全局配置文件application.yml
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/test?serverTimezone=UTC
username: root
password: kenewstar
jpa:
hibernate:
#生成DDL语句，自动创建表
ddl-auto: update
#控制台打印执行的SQL语句
show-sql: true
四、创建用户实体类User
/**
* @Author: kenewstar
* @Description: 用户实体类
* @Date:Created in 2020/6/26
*/
@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String username;
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;
}
}
五、创建UserRepository接口继承JpaRepository接口
/**
* @Author: kenewstar
* @Description: 数据访问层，无需添加任何方法，只需继承JpaRepository接口即可
* @Date:Created in 2020/6/26
*/
@Repository
public interface UserRepository extends JpaRepository<User,Integer> {
}
六、创建SpringBoot启动类
/**
* @Author: kenewstar
* @Description: SprnigBoot启动类
* @Date:Created in 2020/6/26
*/
@SpringBootApplication
public class App {
public static void main(String[] args) {
//springboot启动
SpringApplication.run(App.class,args);
}
}
七、创建测试类TestUserRepository
插入一条数据和更新一条数据均可使用save()方法，SpringDataJPA会自动判断数据库中是否存在该数据，若已存在，则更新，若不存在则插入；
SpringDataJPA源码如下：
org.springframework.data.jpa.repository.support.SimpleJpaRepository类
/*
* (non-Javadoc)
* @see org.springframework.data.repository.CrudRepository#save(java.lang.Object)
*/
@Transactional
@Override
public <S extends T> S save(S entity) {
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity);
}
}
SpringDataJPA测试类
import com.kenewstar.App;
import com.kenewstar.entity.User;
import com.kenewstar.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.SpringJUnit4ClassRunner;
import java.util.List;
/**
* @Author: kenewstar
* @Description: 测试SpringBoot整合SpringDataJPA进行增删改查
* @Date:Created in 2020/6/26
*/
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = {App.class})
public class TestUserRepository {
@Autowired
private UserRepository userRepository;
/**
* 添加一个User
*/
@Test
public void testInsertUser(){
User user = new User();
user.setUsername("kenewstar1");
this.userRepository.save(user);
}
/**
* 根据id删除User
*/
@Test
public void testDelete(){
this.userRepository.deleteById(1);
}
/**
* 修改User
*/
@Test
public void testUpdate(){
User user = new User();
user.setId(2);
user.setUsername("kenewstar2");
this.userRepository.saveAndFlush(user);
}
/**
* 查询所有
*/
@Test
public void findAll(){
List<User> users = userRepository.findAll();
for (User user:users){
System.out.println(user.getId()+"---"+user.getUsername());
}
}
}
八、SpringDataJPA的接口
1.Repository接口
2.CrudRepository接口
3.PagingAndSortingRepository接口
4.JpaRepository接口
5.JpaSpecificationExecutor
创建接口继承JpaSpecificationExecutor接口
/**
* @Author: kenewstar
* @Description: JpaSpecificationExecutor
* @Date:Created in 2020/6/27
*/
public interface UserRepositorySpecification extends
JpaRepository<User,Integer>, JpaSpecificationExecutor<User> {
}
创建测试类
/**
* @Author: kenewstar
* @Description:
* @Date:Created in 2020/6/27
*/
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = App.class)
public class TestUserRepositorySepcification {
@Autowired
private UserRepositorySpecification userRepositorySpecification;
/**
* 单条件查询
*/
@Test
public void testSelect1(){
//封装查询条件
Specification<User> specification = new Specification<User>() {
@Override
public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
/**
* 参数一：获取查询条件属性
* 参数二：获取查询属性的值
*/
Predicate pre = criteriaBuilder.equal(root.get("username"), "kenewstar2");
return pre;
}
};
//执行查询
List<User> users = this.userRepositorySpecification.findAll(specification);
for (User user : users){
System.out.println(user);
}
}
/**
* 多条件查询
*/
@Test
public void testSelect2(){
//封装查询条件
Specification<User> specification = new Specification<User>() {
@Override
public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
List<Predicate> list = new ArrayList<>();
list.add(criteriaBuilder.equal(root.get("username"),"kenewstar3"));
list.add(criteriaBuilder.equal(root.get("id"),3));
//不能使用list.toArray()强转为 Predicate[] 类型
Predicate predicate = criteriaBuilder.and(list.toArray(new Predicate[list.size()]));
return predicate;
}
};
//执行查询
List<User> users = this.userRepositorySpecification.findAll(specification);
for (User user : users){
System.out.println(user);
}
}
}
还可以进行排序查询，分页查询
九、关联查询
用户与角色关联
每个用户对应一个角色
每个角色有多个用户
（一对多关联查询）
1.创建User实体类
/**
* @Author: kenewstar
* @Description: 用户实体类
* @Date:Created in 2020/6/26
*/
@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String username;
@ManyToOne(cascade = CascadeType.MERGE) //级联操作，角色表中没有的角色，执行时进行添加操作，使用CascadeType.PERSIST
@JoinColumn(name = "rid") //外键
private Role role;
public Role getRole() {
return role;
}
public void setRole(Role role) {
this.role = role;
}
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;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
'}';
}
}
2.创建Role实体类
/**
* @Author: kenewstar
* @Description:
* @Date:Created in 2020/6/26
*/
@Entity
@Table(name = "role")
public class Role {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name; //角色名称
@OneToMany(mappedBy = "role") //对应User对象中role属性名称
private Set<User> users = new HashSet<>();
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
3.创建UserRepository接口继承JpaRepository接口
package com.kenewstar.repository;
import com.kenewstar.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
/**
* @Author: kenewstar
* @Description: 数据访问层，无需添加任何方法，只需继承JpaRepository接口即可
*/
@Repository
public interface UserRepository extends JpaRepository<User,Integer> {
}
4.创建测试类测试关联操作
import com.kenewstar.App;
import com.kenewstar.entity.Role;
import com.kenewstar.entity.User;
import com.kenewstar.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.SpringJUnit4ClassRunner;
import java.util.List;
import java.util.Optional;
/**
* @Author: kenewstar
* @Description: 测试关联操作
* @Date:Created in 2020/6/27
*/
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = App.class)
public class TestOneToMany {
@Autowired
private UserRepository userRepository;
@Test
public void testInsert(){
//创建用户
User user = new User();
user.setId(6); //设置了Id，则执行修改用户操作
user.setUsername("kenewstar6");
//创建角色
Role role = new Role();
role.setId(2); //设置了Id则给相应的用户添加对应的外键，不创建新的角色，未设置Id,则会在数据库中角色表添加一个新角色，User表中必须使用CascadeType.PERSIST
role.setName("user");
//关联操作
user.setRole(role);
role.getUsers().add(user);
//持久化
//user与role级联操作
this.userRepository.save(user);
}
@Test
public void testSelect(){
Optional<User> optional = this.userRepository.findById(5);
User user = optional.get();
System.out.println(user);
System.out.println(user.getRole().getName());
}
@Test
public void findAll(){
List<User> users = this.userRepository.findAll();
for (User user:users){
System.out.println(user+"---"+user.getRole().getName());
}
}
}