Spring Data JPA动态查询

默认的 JPA 可以做简单的查询，当我们遇到多条件时怎么动态的来查询数据，这里使用 Specification 来解决这个问题

一、使用

Dao 接口需要继承 JpaRepository 之外，还需要继承 JpaSpecificationExecutor

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

import com.ustcinfo.thinkcloud.common.entity.rbac.User;

public interface UserRepo extends JpaRepository<User, Integer>, JpaSpecificationExecutor<User> {
}

实现多条件的查询：

import java.util.ArrayList;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;

import com.ustcinfo.thinkcloud.common.entity.rbac.User;
import com.ustcinfo.thinkcloud.common.repository.rbac.UserRepo;

@Service
public class UserService {

	@Autowired
	private UserRepo userRepo;

	/**
	 * JPA动态查询
	 */
	public List<User> find(User user) {

		// Specification查询构造器
		Specification<User> specification = new Specification<User>() {

			private static final long serialVersionUID = 1L;

			@Override
			public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder criteriaBuilder) {
				List<Predicate> predicates = new ArrayList<>();
				// 添加搜索条件
				if (null != user.getId()) {
					predicates.add(criteriaBuilder.equal(root.get("id"), user.getId())); // id是表字段
				}
				if (StringUtils.isNotBlank(user.getName())) {
					predicates.add(criteriaBuilder.like(root.get("name"), user.getName()));
				}
				// 把搜索条件连接（AND）起来
				return criteriaBuilder.and(predicates.toArray(new Predicate[predicates.size()]));
			}
		};
		return userRepo.findAll(specification);
	}

}