Java for Web学习笔记（一二一）：搜索（3）JPA的动态条件搜索（下）

例子的具体实现

仓库的实现

使用spring data，增加自定义接口SearchableRepository，具体如下：

public interface PersonRepository extends CrudRepository<Person, Long>, SearchableRepository<Person>{
}

public class PersonRepositoryImpl extends AbstractSearchableJpaRepository<Person>{
}

service的实现

public interface PersonService {
	... ...
	Page<Person> searchPeople(SearchCriteria searchCriteria, Pageable pageable);
}

@Service
public class DefaultPersonService implements PersonService{
	@Inject PersonRepository repository;

	......

	@Override
	@Transactional
	public Page<Person> searchPeople(SearchCriteria searchCriteria, Pageable pageable) {
		return this.repository.search(searchCriteria, pageable);
	}
}

controller的实现

public String find(Map<String, Object> model, SearchForm form,Pageable pageable) throws ParseException{
	SearchCriteria criteria = SearchCriteria.Builder.create();
	if(form.isIncludeFirstName())
		criteria.add(new Criterion("firstName", Criterion.Operator.EQ, form.getFirstName()));
	if(form.isIncludeMiddleInitial())
		criteria.add(new Criterion("middleInitial", Criterion.Operator.EQ, form.getMiddleInitial()));
        if(form.isIncludeLastName())
		criteria.add(new Criterion("lastName", Criterion.Operator.EQ, form.getLastName()));
        if(form.isIncludeState())
		criteria.add(new Criterion("state", Criterion.Operator.EQ, form.getState()));
        if(form.isIncludeCountry())
		criteria.add(new Criterion("country", Criterion.Operator.EQ, form.getCountry()));
        if(form.isIncludeBirthDate())
		criteria.add(new Criterion("birthDate", Criterion.Operator.EQ, 
			new Date(new SimpleDateFormat(dateFormatter).parse(form.getBirthDate()).getTime() )));
        if(form.isIncludeGender())
		criteria.add(new Criterion("gender", Criterion.Operator.EQ, form.getGender()));
        if(form.isIncludeRace())
		criteria.add(new Criterion("race", Criterion.Operator.EQ, form.getRace()));
        if(form.isIncludeEthnicity())
		criteria.add(new Criterion("ethnicity", Criterion.Operator.EQ, form.getEthnicity()));
        
        model.put("searchForm", form);
        model.put("results", this.personService.searchPeople(criteria, pageable));
        
	return "people/find";
}

对于OR

我们可以看出通用的Criteria JPA查询功能很强大，但也很危险，用户可能会进行任意的查询，影响了性能。

在例子中，我们只给出了AND的方式，其实OR的方式也是类型。我们看看JPA如何处理AND和OR同时存在的条件。

//【例子1】名字中有n的无论是姓还是名（OR），同时要求生日为b（AND）关系。
criteria.select(root).where(
           builder.or(
               builder.equal(root.get("lastName"), n),
               builder.equal(root.get("firstName"), n)
           ),
           builder.equal(root.get("birthDate"), b)
);
//【例子2】和例子1一样，只要是体现一个AND和OR嵌入的关系
criteria.select(root).where(
           builder.and(
               builder.or(
                   builder.equal(root.get("lastName"), n),
                   builder.equal(root.get("firstName"), n)
               ),
               builder.equal(root.get("birthDate"), b)
           )
);
//【例子3】基于嵌入关系，提供的要给复杂的例子
pageCriteria.select(pageRoot).where(
          builder.or(
              builder.and(
                  builder.equal(expr),
                  builder.equal(expr),
                  pageRoot.get("property").in(expr)
              ),
              builder.or(
                  builder.lessThan(expr),
                  builder.greaterThanOrEqualTo(expr)
              )
          ),
          builder.and(
              builder.equal(expr),
              builder.greaterThan(expr)
          )
);

相关链接：我的Professional Java for Web Applications相关文章