jpa接口详解

快来打我* 2022-12-02 01:15 246阅读 0赞

### jpa接口详解 ###

*  Repository
 *  CrudRepository
 *  PagingAndSortingRepository
 *  QueryByExampleExecutor

@Data
    @Entity // 声明这个类对应了一个数据库表
    @Table(name = "BB_CLOTHES") // 声明了数据库实体对应的表信息,如果没有指定，则表名和实体的名称保持一致
    public class Clothes implements Serializable{ 
    	private static final long serialVersionUID = -3018808522887346432L;
    	@Id
    	@GeneratedValue(strategy=GenerationType.IDENTITY)//主键由数据库自动生成
    	private Long id;
    
    	@Column(length = 32)
    	private String name;
    
    	@Column(length = 32)
    	private Integer size;
    
    	@Column(length = 64)
    	private Float price;
    }

![在这里插入图片描述][20200829085518966.png_pic_center]

# Repository #

中央存储库标记接口  
T： 实体类  
ID： 实体类的主键类型

@Indexed
    public interface Repository<T, ID> { 
    }

# CrudRepository #

通用的增删改查接口

public interface CrudRepository<T, ID> extends Repository<T, ID> { 
    	<S extends T> S save(S entity);
    	<S extends T> Iterable<S> saveAll(Iterable<S> entities);
    	Optional<T> findById(ID id);
    	boolean existsById(ID id);
    	Iterable<T> findAll();
    	Iterable<T> findAllById(Iterable<ID> ids);
    	long count();
    	void deleteById(ID id);
    	void delete(T entity);
    	void deleteAll(Iterable<? extends T> entities);
    	void deleteAll();
    }

@Autowired ClothesDao clothesDao;
    
    	@GetMapping("/testCrudRepository")
    	Object testCrudRepository(Clothes clothes) { 
    		log.info("【clothes】={}", clothes);
    		// 保存对象
    		clothesDao.save(clothes);
    
    		// 保存列表里面的对象 对每条记录分别执行 insert into bb_clothes (name, price, size) values (?, ?, ?)
    		ArrayList<Clothes> saveList = new ArrayList<>();
    		Clothes saveO1 = new Clothes();saveO1.setName("save1");
    		Clothes saveO2 = new Clothes();saveO2.setName("save2");
    		saveList.add(saveO1);
    		saveList.add(saveO2);
    		clothesDao.saveAll(saveList);
    
    		// 根据id查找 返回 Optional<Clothes> 对象
    		Optional<Clothes> clothesOpt = clothesDao.findById(1l);
    		clothesOpt.ifPresent(c -> log.info("【findById】={}", c));
    
    		// 根据id查找记录是否存在
    		log.info("【existsById】={}", clothesDao.existsById(1l));
    
    		// 查找全部
    		log.info("【findAll】={}", clothesDao.findAll());
    
    		// 查找指定id列表对应的对象列表
    		List<Long> idList = new ArrayList<>();
    		idList.add(1l);
    		idList.add(2l);
    		log.info("【findAllById】.Iterable={}", clothesDao.findAllById(idList));
    
    		log.info("【count】={}", clothesDao.count());
    
    		// 根据id删除, 先查询数据库是否有该记录，如果有删除，否则删除不存在数据会抛出异常
    		Optional<Clothes> beDeleteObject = clothesDao.findById(9l);
    		beDeleteObject.ifPresent(c -> clothesDao.delete(c));
    
    		// 最终执行的删除操作 delete from bb_clothes where id=?
    		Optional<Clothes> opt = clothesDao.findById(24l);
    		opt.ifPresent(c -> { 
    			clothesDao.delete(c);
    		});
    
    		// 删除所有数据 select * from bb_clothes;
    		// 对每条记录 delete from bb_clothes where id=?
    		// clothesDao.deleteAll();
    
    		// 对每条记录遍历删除 delete from bb_clothes where id=?
    		List<Clothes> deleteList = clothesDao.findAllById(idList);
    		clothesDao.deleteAll(deleteList);
    
    		return deleteList;
    	}

# PagingAndSortingRepository #

增加分页和排序功能

@NoRepositoryBean
    public interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> { 
    	Iterable<T> findAll(Sort sort);
    	Page<T> findAll(Pageable pageable);
    }

@SuppressWarnings("unused")
    	@GetMapping("/testPagingAndSortingRepository")
    	Object testPagingAndSortingRepository(Clothes clothes) { 
    		// 指定排序字段查找全部
    		Sort sort01 = new Sort(Direction.ASC, "name");
    		Sort sort02 = Sort.by(Direction.ASC, "name");
    		Order idOrder = new Order(Direction.DESC, "id");
    		Order idOrder2 = new Order(Direction.DESC, "name");
    		Sort sort03 = Sort.by(idOrder,idOrder2);
    		Sort sort04 = Sort.by(Direction.ASC, "id", "name");
    		Sort sort05 = Sort.by("id", "name");
    		log.info("【findAll】.sort={}", clothesDao.findAll(sort01));
    
    		int pageIndex = 1;
    		Pageable pageable=PageRequest.of(pageIndex-1, 2,sort01);
    		Pageable pageable02 = PageRequest.of(pageIndex-1, 2, Direction.ASC, "id");
    		Pageable pageable03 = PageRequest.of(pageIndex-1, 2, Direction.ASC, "id", "name");
    		Page<Clothes> page = clothesDao.findAll(pageable);
    		return page;
    	}

# QueryByExampleExecutor #

public interface QueryByExampleExecutor<T> { 
    	<S extends T> Optional<S> findOne(Example<S> example);
    	<S extends T> Iterable<S> findAll(Example<S> example);
    	<S extends T> Iterable<S> findAll(Example<S> example, Sort sort);
    	<S extends T> Page<S> findAll(Example<S> example, Pageable pageable);
    	<S extends T> long count(Example<S> example);
    	<S extends T> boolean exists(Example<S> example);
    }

@RestController
    @RequestMapping("/example")
    @Slf4j
    public class QueryByExampleController { 
    	@Autowired ClothesDao clothesDao;
    	@GetMapping("/findOne")
    	Object findOne(Long id) { 
    		// 1、 精准匹配对象，查出多条会报错
    		Clothes ClothesObject = new Clothes();
    		ClothesObject.setId(id);
    		Example<Clothes> example = Example.of(ClothesObject);
    		Optional<Clothes> optClothes = clothesDao.findOne(example);
    		optClothes.ifPresent(c -> log.info("【findOne】.sort={}", c));
    		return optClothes.get();
    	}
    	@GetMapping("/findAll")
    	Object findAll() { 
    		Clothes Clothes = new Clothes();
    		Clothes.setName("黑");
    
    		ExampleMatcher matcher = ExampleMatcher.matching();
    		// 注意matcher.withMatcher返回一个新的对象
    		matcher = matcher.withMatcher("name", match -> match.startsWith());
    		// matcher = matcher.withMatcher("name", match -> match.regex());
    		// matcher = matcher.withMatcher("name", match -> match.endsWith());
    		// matcher = matcher.withMatcher("name", match -> match.contains());
    		// matcher = matcher.withIgnorePaths("name");
    		// ExampleMatcher matcher = ExampleMatcher.matching().withMatcher("name", ExampleMatcher.GenericPropertyMatchers.endsWith());
    		Example<Clothes> example = Example.of(Clothes, matcher);
    
    		Sort sort = Sort.by(Direction.ASC, "name");
    		List<Clothes> findAll = clothesDao.findAll(example, sort);
    		log.info("【findAll】.example, sort, {}", findAll);
    		return findAll;
    	}
    	@GetMapping("/getPage")
    	Object getPage() { 
    		Clothes Clothes = new Clothes();
    		Clothes.setName("衬衫");
    
    		ExampleMatcher matcher = ExampleMatcher.matching();
    		matcher = matcher.withMatcher("name", match -> match.contains());
    		Example<Clothes> example = Example.of(Clothes, matcher);
    
    		Pageable pageable = PageRequest.of(0, 15, Direction.DESC, "name");
    		Page<Clothes> page = clothesDao.findAll(example, pageable);
    		log.info("【findAll】.example, pageable={}", page);
    		return page;
    	}
    }

[20200829085518966.png_pic_center]: /images/20221123/8169a3f8a22848a482a5d9a9120b883a.png