Spring JPA find单表查询方法示例详解

@Override
public Optional<T> findById(ID id) {
   Assert.notNull(id, ID_MUST_NOT_BE_NULL);
   Class<T> domainType = getDomainClass();
   if (metadata == null) {
      return Optional.ofNullable(em.find(domainType, id));
   }
   LockModeType type = metadata.getLockModeType();
   Map<String, Object> hints = new HashMap<>();
   getQueryHints().withFetchGraphs(em).forEach(hints::put);
   return Optional.ofNullable(type == null ? em.find(domainType, id, hints) : em.find(domainType, id, type, hints));
}

@Override
public List<T> findAll() {
   return getQuery(null, Sort.unsorted()).getResultList();
}

@Override
public List<T> findAllById(Iterable<ID> ids) {
   Assert.notNull(ids, "Ids must not be null!");
   if (!ids.iterator().hasNext()) {
      return Collections.emptyList();
   }
   if (entityInformation.hasCompositeId()) {
      List<T> results = new ArrayList<>();
      for (ID id : ids) {
         findById(id).ifPresent(results::add);
      }
      return results;
   }
   Collection<ID> idCollection = Streamable.of(ids).toList();
   ByIdsSpecification<T> specification = new ByIdsSpecification<>(entityInformation);
   TypedQuery<T> query = getQuery(specification, Sort.unsorted());
   return query.setParameter(specification.parameter, idCollection).getResultList();
}

@GetMapping("findAllById")
public List<User> findAllById(Integer[] ids) {
    return userService.findAllById(Arrays.asList(ids));
}

@Override
public List<T> findAll(Sort sort) {
   return getQuery(null, sort).getResultList();
}

/**
 * Creates a new {@link Sort} for the given {@link Order}s.
 *
 * @param direction must not be {@literal null}.
 * @param properties must not be {@literal null}.
 * @return
 */
public static Sort by(Direction direction, String... properties) {
   Assert.notNull(direction, "Direction must not be null");
   Assert.notNull(properties, "Properties must not be null");
   Assert.isTrue(properties.length > 0, "At least one property must be given");
   return Sort.by(Arrays.stream(properties)//
         .map(it -> new Order(direction, it))//
         .collect(Collectors.toList()));
}

@GetMapping("findAllSort")
public List<User> findAllSort(String ascOrDesc, String[] para) {
    Sort sort;
    if(ascOrDesc.toLowerCase().equals("desc")){
        sort = Sort.by( Sort.Direction.DESC, para);
    }else {
        sort = Sort.by( Sort.Direction.ASC, para);
    }
    return userService.findAllSort(sort);
}

[{
	"id": 21,
	"name": "bb",
	"age": 12
}, {
	"id": 22,
	"name": "cc",
	"age": 11
}, {
	"id": 20,
	"name": "aa",
	"age": 11
}]

/**
 * Creates a new {@link Sort} for the given {@link Order}s.
 *
 * @param orders must not be {@literal null}.
 * @return
 */
public static Sort by(List<Order> orders) {
   Assert.notNull(orders, "Orders must not be null");
   return orders.isEmpty() ? Sort.unsorted() : new Sort(orders);
}
/**
 * Creates a new {@link Sort} for the given {@link Order}s.
 *
 * @param orders must not be {@literal null}.
 * @return
 */
public static Sort by(Order... orders) {
   Assert.notNull(orders, "Orders must not be null");
   return new Sort(Arrays.asList(orders));
}

@GetMapping("findAllMoreSort")
public List<User> findAllMoreSort(String[] sorts,String[] paras) {
    int length = sorts.length;
    //Sort.Order[] orders = new Sort.Order[length];
    List<Sort.Order> listOrder = new ArrayList<>();
    for(int i=0; i<length; i++){
//      orders[i] = new Sort.Order(sorts[i].toLowerCase().equals("asc") ?
//                        Sort.Direction.ASC : Sort.Direction.DESC, paras[i]);
        listOrder.add(new Sort.Order(sorts[i].toLowerCase().equals("asc") ?
                            Sort.Direction.ASC : Sort.Direction.DESC, paras[i]));
    }
    //Sort sort = Sort.by(orders);
    Sort sort = Sort.by(listOrder);
    return userService.findAllSort(sort);
}

[{
	"id": 22,
	"name": "cc",
	"age": 11
}, {
	"id": 20,
	"name": "aa",
	"age": 11
}, {
	"id": 21,
	"name": "bb",
	"age": 12
}]