SpringData JPA quick start
SpringBoot integrates SpringData-JPA quick start,
A SpringBoot configuration SpringData-JPA
1 Introduce dependencies
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
2 configuration
Configure application.properties
server.port=4321
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/website?useUnicode=true&characterEncoding=UTF8&useSSL=false&serverTimezone=Asia/Shanghai
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=root
#是否自动生成实体类对应的数据库表 true为自动生成表，false不自动生成
spring.jpa.generate-ddl=false
#数据库类型
spring.jpa.database=mysql
#打印日志
spring.jpa.show-sql=true
#方言设置
spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect
Add comment
@SpringBootApplication
@EnableJpaRepositories(basePackages = "com.mt.mapper")
public class Jpa01Application {
public static void main(String[] args) {
SpringApplication.run(Jpa01Application.class, args);
}
}
Additions, deletions, and changes to the second single table
SpringData-JPA provides us with JpaRepository and JpaSpecificationExecutor interfaces, we only need to write the interface to inherit these two interfaces to realize the addition, deletion, modification, and check operation
Example of single table query:
entity:
@NoArgsConstructor
@AllArgsConstructor
@Data
@Entity //标注该类为数据库映射类
@Table(name = "mt_product_info") //默认获取类名转下划线作为对应的表，可以通过@table标注对应的表
public class MtProductInfo {
@Id //标注为主键
@GeneratedValue(strategy = GenerationType.IDENTITY)//标注id生成策略
private Integer id;
private String name;
private String summarize;
private Integer headImg;
private Integer productId;
private Integer sort;
private Integer status;
private Date createTime;
private String indexName;
private Integer indexIcon;
private Integer indexSort;
@Column(name = "index_isshow") //标注属性对应的字段，不加默认属性名转下划线
private Integer indexIsShow;
private String indexDesc;
private Integer systemImg;
}
repository:
public interface MtProductInfoMapper extends JpaRepository<MtProductInfo,Integer>, JpaSpecificationExecutor<MtProductInfo> {
}
test:
@SpringBootTest
class Jpa02ApplicationTests {
@Autowired
private MtProductInfoMapper infoMapper;
@Test
void contextLoads() {
List<MtProductInfo> productInfoList = infoMapper.findAll();
productInfoList.forEach( System.out::print);
}
}
Add to
Directly through the save method provided by JPARepository
@Test
public void add(){
//如果没id 为添加，否则为修改，修改会重新设置所有字段值，不会忽略null
MtProductInfo info = new MtProductInfo();
info.setName("test1");
info.setStatus(0);
infoMapper.save(info);
}
delete
method one
@Test
public void delete(){
infoMapper.deleteById(71);
}
Method 2: @query
@Transactional
@Modifying
@Query("delete from MtProductInfo where name = :name")
public void delete(String name);
modify
Method 1: Provided by JPARepository
@Test
public void update(){
MtProductInfo info = new MtProductInfo();
info.setName("test1");
info.setStatus(0);
info.setId(1); //设置了id即为修改，这里只将name修改为test1，状态修改为0 其他字段全部为null
infoMapper.save(info);
}
Method 2: Modify via @query, create a modification method in the repository interface, and annotate via @Query
@Transactional //修改需要事务支持
@Modifying //增删改必须标注@Modifying
@Query("update MtProductInfo set name = :#{#productInfo.name} ,status=:#{#productInfo.status}")
public void update( MtProductInfo productInfo );
//也可以这样写
@Transactional
@Modifying
@Query("update MtProductInfo set name = :name ,status=:status where id = :id")
public void update( String name,Integer status,Integer id );
Inquire
Method 1: Query through the method provided by JpaRepository
@Test
public void query(){
//根据id 查询
Optional<MtProductInfo> infoOp = infoMapper.findById(1);
if(infoOp.isPresent()){
System.out.println("查询到对象===>"+infoOp.get());
}else{
System.out.println("对象不存在");
}
//如果查询为null 这返回传入的对象否则返回数据库对象
infoOp.orElse(new MtProductInfo());
List<MtProductInfo> all = infoMapper.findAll();
}
Method 2: Query by custom method name
A powerful feature of SpringData-Jpa is that you can create query conditions by splicing method names
//where name like '' and status =1
public List<MtProductInfo> queryByNameLikeAndStatusEqualsOrderBySortDesc(String name,Integer status);
Method 3: Query custom conditions through the method provided by JpaSpecificationExecutor
@Test
@Test
public void query3(){
List<MtProductInfo> infoList = infoMapper.findAll(new Specification<MtProductInfo>() {
@Override
public Predicate toPredicate(Root<MtProductInfo> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
Path<String> name = root.get("summarize"); //数据库名称
Path<String> status = root.get("status"); //数据库名称
Predicate nameLike = criteriaBuilder.like(name, "%人大%");
Predicate statusEq = criteriaBuilder.equal(status, 1);
return criteriaBuilder.and(nameLike,statusEq);
}
});
infoList.forEach(System.out::println);
}
Sort
@Test
public void query3(){
//排序，注意这里出入的是属性名不是字段名
Sort sort = Sort.by(Sort.Direction.DESC, "createTime").and(Sort.by(Sort.Direction.ASC, "name"));
List<MtProductInfo> infoList = infoMapper.findAll(new Specification<MtProductInfo>() {
@Override
public Predicate toPredicate(Root<MtProductInfo> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
Path<String> name = root.get("summarize"); //数据库名称
return criteriaBuilder.like(name, "%人大%");
}
},sort);
//排序，传入的是属性名称，不是数据库字段名
infoList.forEach(System.out::println);
}
Pagination
@Test
public void query4(){
//分页查询 注意页数从0开始
Page<MtProductInfo> page = infoMapper.findAll(PageRequest.of(0, 2,Sort.by(Sort.Direction.ASC,"createTime")));
System.out.println("当前总页数==>"+page.getTotalPages() );
System.out.println("当前总条数==>"+page.getTotalElements() );
System.out.println("是否有上一页==>"+page.hasPrevious());
System.out.println("是否有下一页==>"+page.hasNext());
System.out.println("========================");
page.getContent().forEach(System.out::println);
}