Question

我已经编写了简单的代码来查询具有多个（可选）参数的JPA，就像这样：

@Getter
@Setter
 public class SearchCriteria {
  private String key;
  private Object value;
  private SearchOperation operation;

 public SearchCriteria(String key, Object value, SearchOperation operation) {
  this.key = key;
  this.value = value;
  this.operation = operation;
 }
}

SearchOption类：

public enum SearchOperation {
 GREATER_THAN,
 LESS_THAN,
 GREATER_THAN_EQUAL,
 LESS_THAN_EQUAL,
 NOT_EQUAL,
 EQUAL,
 MATCH,
 MATCH_END,
 BETWEEN_DATE,
 GREATER_THAN_DATE,
 LESS_THAN_DATE;
}

还有一个GenericSpecification类：

 public class GenericSpecification<T> implements Specification<T> {

 private SimpleDateFormat localeIta = new SimpleDateFormat("dd/MM/yyyy");
 private List<SearchCriteria> list;

 public GenericSpecification() {
 this.list = new ArrayList<>();
 }

 public void add(SearchCriteria criteria) {
 list.add(criteria);
 }

 @Override
 public Predicate toPredicate(Root<T> root, CriteriaQuery<?> query, CriteriaBuilder builder) {

 List<Predicate> predicates = new ArrayList<>();

 for (SearchCriteria criteria : list) {
 switch(criteria.getOperation()) {
 ....
 case BETWEEN_DATE: {
   Path<Date> entityDate = root.get(criteria.getKey());
   predicates.add(builder.between(entityDate, getComparingDates((String[])criteria.getValue(), 0), getComparingDates((String[])criteria.getValue(), 1)));
  }
 break;
 }
return builder.and(predicates.toArray(new Predicate[0]));
}

这是用于带有参数的构建查询，即使它们被价目化，例如：

GenericSpecification spec = new GenericSpecification<CreditCard>:
If (param != null) spec.add(new SearchCriteria("fieldName", param, SearchOperation.OPE));

如果设置了某些参数，现在我必须联接几个表。使用metamodel或Specification执行联接的最佳方法是什么？

JPA规范多个联接

0 个答案: