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这是江帅帅的第010篇原创
Spring Data JPA
使用：将数据访问层接口实现 JpaRepository 接口即可完成 Spring Data JPA 访问数据。
JpaRepository 极大简化了 JPA 作为数据访问的代码。
今天给大家介绍几个案例：
- 简单条件查询
- 关联查询和 @Query 查询
- @NamedQuery 查询
- Specification 查询
案例1：简单条件的查询
1）编辑 pom.xml 文件（与 CrudRepository 接口案例一样）
2）编辑 application.properties 文件（与 CrudRepository 接口案例一样）
3）创建 Student 持久化类
package nx.bean; import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; // 学生 @Entity @Table(name="tb_student") // 学生表 public class Student implements Serializable{ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private int id; private String name ; // 名字 private String address ; // 地址 private int age ; // 年龄 private char sex; // 性别 // getXxx & setXxx 方法 }
4）创建 StudentRepository 数据访问接口
package nx.repository; import java.util.List; import nx.bean.Student; import org.springframework.data.jpa.repository.JpaRepository; public interface StudentRepository extends JpaRepository<Student, Integer> { /** * 通过学生姓名来查询学生对象 * 此方法相当于JPQL语句代码 * select s from Student s where s.name = ?1 */ Student findByName(String name); /** * 通过名字和地址查询学生信息 * 此方法相当于JPQL语句代码 * select s from Student s where s.name = ?1 and s.address=?2 */ List<Student> findByNameAndAddress(String name , String address); /** * 通过学生姓名模糊查询学生信息 * 此方法相当于JPQL语句代码 * select s from Student s where s.name like ?1 */ List<Student> findByNameLike(String name); }
5）创建 StudentService 业务层类
package nx.service; import java.util.List; import javax.annotation.Resource; import nx.bean.Student; import nx.repository.StudentRepository; import org.springframework.stereotype.Service; import org.springframework.transaction.annotation.Transactional; @Service public class StudentService { // 注入数据访问层接口对象 @Resource private StudentRepository studentRepository; // 保存所有 @Transactional public void saveAll(List<Student> students) { studentRepository.saveAll(students); } // 根据名字查找 public Student getStuByName(String name) { return studentRepository.findByName(name); } // 根据名字和地址查找 public List<Student> getStusByNameAndAddress(String name,String address) { return studentRepository.findByNameAndAddress(name,address); } // 根据名字模糊查询 public List<Student> getStusByNameLike(String name) { return studentRepository.findByNameLike("%"+name+"%"); } }
6）创建 StudentController 控制器类
package nx.controller; import java.util.ArrayList; import java.util.List; import javax.annotation.Resource; import nx.bean.Student; import nx.service.StudentService; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping("/student") public class StudentController { // 注入StudentService @Resource private StudentService studentService; @RequestMapping("/save") public String save() { Student s1 = new Student(); s1.setAddress("广州"); s1.setName("帅帅"); s1.setAge(18); s1.setSex('男'); Student s2 = new Student(); s2.setAddress("广州"); s2.setName("花花"); s2.setAge(17); s2.setSex('女'); List<Student> students = new ArrayList<>(); students.add(s1); students.add(s2); studentService.saveAll(students); return "保存student对象成功"; } @RequestMapping("/name") public Student getByName(String name) { return studentService.getStuByName(name); } @RequestMapping("/nameAndAddress") public List<Student> getByNameAndAddress(String name,String address) { return studentService.getStusByNameAndAddress(name, address); } @RequestMapping("/nameLike") public List<Student> getByNameLile(String name) { return studentService.getStusByNameLike(name); } }
7）访问测试
http://localhost:8080/student/nameLike?name=帅
