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;

}

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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;
    }
}