Spring Data JPA 查询
1.命名查询 在StudentRepository接口中 定义命名查询，不需要实现类 参考使用 Spring Data JPA 简化 JPA 开发
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.stereotype.Repository;
@Repository
public interface StudentRepository extends JpaRepository,JpaSpecificationExecutor {
Student findByName(String name);
}
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class StudentServiceImpl implements StudentService {
@Autowired
private StudentRepository studentRepository;
@Override
public Student findByName(String name) {
Student student = studentRepository.findByName(name); //使用命名查询
System.out.println("==============student===" + student.toString());
return null;
}
}
2.分页查询 pageNumber是从0开始， pageNumber=0,pageSize=3 就是获取前3条 参考创建分页Pageable变量
创建Pageable对象，再查询
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.domain.Sort.Direction;
import org.springframework.stereotype.Service;
@Service
public class StudentServiceImpl implements StudentService {
@Autowired
private StudentRepository studentRepository;
// 分页获取
@Override
public List findAllPageable(Integer pageNumber, Integer pageSize) {
Pageable pageable = new PageRequest(pageNumber, pageSize); // 创建分页对象
Page students = studentRepository.findAll(pageable);
Long total = students.getTotalElements(); // 符合条件的总记录条数
List studentsList = students.getContent();// 这一页的所有记录
return null;
}
}
3.先排序 再分页 查询 : 创建Sort对象，再用Sort对象创建 Pageable对象，再查询 参考Spring Data JPA 多属性排序
根据一个字段排序
Sort sort = new Sort(Direction.DESC, "homeTel");// 排序方式 根据homeTel降序排列 多属性排序 根据多个字段排序，排序方式一样
Sort sort = new Sort(Sort.Direction.DESC, "homeTel", "name");// 根据homeTel和name降序排列 多属性排序 根据多个字段排序，排序方式不一样
//先根据homeTel降序排列,再根据name的升序排列
Sort sort = new Sort(Direction.DESC, "homeTel").and(new Sort(Direction.ASC, "name"));@Service
public class StudentServiceImpl implements StudentService {
@Autowired
private StudentRepository studentRepository;
//根据条件排序 再分页获取
@Override
public List findAllPageableBySort(Integer pageNumber, Integer pageSize) {
Sort sort = new Sort(Direction.DESC, "homeTel");// 排序方式 根据homeTel降序排列
Pageable pageable = new PageRequest(pageNumber, pageSize, sort);// 分页对象
Page students = studentRepository.findAll(pageable);// 查询
Long total = students.getTotalElements(); // 符合条件的总记录条数
List studentsList = students.getContent();// 这一页的所有记录
return null;
}
//根据多个条件先排序 再分页获取
@Override
public List findAllPageableByMultiSort(Integer pageNumber, Integer pageSize) {
// 根据多个条件排序 先根据homeTel降序排列,再根据name的升序排列
Sort sort = new Sort(Direction.DESC, "homeTel").and(new Sort(Direction.ASC, "name"));
Pageable pageable = new PageRequest(pageNumber, pageSize, sort);// 分页对象
Page students = studentRepository.findAll(pageable);// 查询
Long total = students.getTotalElements(); // 符合条件的总记录条数
List studentsList = students.getContent();// 这一页的所有记录
return null;
}
}
4.条件化查询 用查询条件创建Specification对象 参考Spring Data JPA Specification查询
使用Criteria查询 Criteria查询是面向对象查询， root就是一个对象，root.get("name")就是name属性。可以级联获取属性
每一个查询条件创建一个Specification对象，如果有多个查询条件，就把多个Specification对象and或or成最后一个总的Specification对象。
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.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;
@Service
public class StudentServiceImpl1 implements StudentService {
@Autowired
private StudentRepository studentRepository;
/*一个查询条件*/
@Override
public List findPageableByParam(Integer pageNumber, Integer pageSize, String name) {
// 1.创建Pageable对象
Pageable pageable = new PageRequest(pageNumber, pageSize);
// 2.根据查询条件 创建Specification对象
Specification specification = new Specification() {
@Override
public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery,
CriteriaBuilder criteriaBuilder) {
Predicate predicate = criteriaBuilder.equal(root.get("name").as(String.class), name);
return predicate;
}
};
// 3.查询
Page students = studentRepository.findAll(specification, pageable);
Long total = students.getTotalElements(); // 符合条件的总记录条数
List studentsList = students.getContent();// 这一页的所有记录
return studentsList;
}
/*多个查询条件*/
@Override
public List findPageableByParams(Integer pageNumber, Integer pageSize, String name, Long homeTel) {
// 1.创建Pageable对象
Pageable pageable = new PageRequest(pageNumber, pageSize);
// 2.根据查询条件 创建Specification对象
Specification specification = new Specification() {
@Override
public Predicate toPredicate(Root root, CriteriaQuery criteriaQuery,
CriteriaBuilder criteriaBuilder) {
// name条件
Predicate namePredicate = criteriaBuilder.like(root.get("name").as(String.class), "%" + name + "%");
// homeTel条件
Predicate predicate = criteriaBuilder.equal(root.get("homeTel").as(Long.class), homeTel);
// and 两个条件
Predicate and = criteriaBuilder.and(namePredicate, predicate);
return and;
}
};
// 3.查询
Page students = studentRepository.findAll(specification, pageable);
Long total = students.getTotalElements(); // 符合条件的总记录条数
List studentsList = students.getContent();// 这一页的所有记录
return studentsList;
}
}
5.Spring Data JPA 原生sql查询 参考 Spring Data JPA @Query
在Repository层 用@Query注解做查询 @Query 默认是按对象查询，nativeQuery = true：按sql原生语句查询
增删改操作 需用要@Modifying注解和@Transactional注解，并且返回值只能是int或者Integer。
import java.util.List;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
@Repository
public interface StudentRepository extends JpaRepository, JpaSpecificationExecutor {
@Query(value = "SELECT * from t_student where id= :id and name like CONCAT('%',:name,'%') ", nativeQuery = true)
List findOneStudent1(@Param("id") Long id, @Param("name") String name);
}
Spring Data JPA提供的查询 很多时候不能满足业务需求，这时候就需要使用原生sql实现查询
5.1.需要按汉语拼音排序
基于oracle数据库，在oracle数据库，把查询结果按汉语拼音排序
select * from TB_STUDENT where class_no = '' order by NLSSORT(student_name,'NLS_SORT=SCHINESE_PINYIN_M')Spring Data JPA原生sql查询
import java.util.List;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
public interface UserRepository extends JpaRepository, JpaSpecificationExecutor {
@Query(value = "select * from TB_STUDENT where class_no = :classNo order by NLSSORT(student_name,'NLS_SORT=SCHINESE_PINYIN_M')", nativeQuery = true)
List findAllByClass(@Param("classNo") String classNo);
} 5.2 只查询部分字段
import java.util.List;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
@Repository
public interface MatrixReportRepository
extends JpaRepository, JpaSpecificationExecutor {
@Query(value = "select username,age from TB_STUDENT Where class_no= :classNo ", nativeQuery = true)
List findSubStudents(@Param("classNo") String classNo);
}
5.3 distinct 或者 group by