SpringData JPA实现CRUD,分页与多参数排序

Posted 若谷先生

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  Spring Data 项目的目的是为了简化构建基于 Spring 框架应用的数据访问计数,包括非关系数据库、Map-Reduce 框架、云数据服务等等,SpringData JPA是简化创建 JPA 数据访问层和跨存储的持久层功能,通过一个接口的继承即可实现简单的CRUD。

  数据库的连接与项目的构建不说了,可以参考:springboot实战SpringDataJPA。我采用的是eclipse构建的普通的springboot项目。

一、创建表与实体类映射

@Entity
@Table(name = "student")
public class Student implements Serializable {
	@Id
	// id自动生成
	@GeneratedValue
	@Column(name = "id")
	private Long id;
	@Column(name = "name")
	private String name;
	@Column(name = "clas")
	private String clas;

	@Column(name = "interest")
	private String interest;

    // 省略了getter(),setter()方法 

二、创建StudentMapper 继承JpaRepository<Student, Long>,第一个参数是实体,第二个参数是主键的类型

public interface StudentMapper extends JpaRepository<Student, Long> {
	// int queryCount();
	// 自定义的方法实现findAll
	@Query(value = "select * from student where id < ?1", nativeQuery = true)
	public List<Student> findAll(Long id);
}

三、Controller内的代码如下:

@Resource
	private FirstPageService firstPageService;

	@RequestMapping(value = "/", method = RequestMethod.GET)
	@Fooish(tags = { "this_is_method" })
	String home() {
		return firstPageService.getString();
	}

	@RequestMapping(value = "/add", method = RequestMethod.GET)
	String addStudent(Student student) {
		return firstPageService.addStudent(student);
	}

	@RequestMapping(value = "/delete", method = RequestMethod.GET)
	String deleteStudent(Long id) {
		return firstPageService.deleteStudent(id);
	}

	@RequestMapping(value = "/update", method = RequestMethod.GET)
	String updateStudent(Student student) {
		return firstPageService.updateStudent(student);
	}

	@RequestMapping(value = "/list", method = RequestMethod.GET)
	List<Student> listStudent() {
		return firstPageService.listStudent();
	}

	// 采用的是自定义的方法
	@RequestMapping(value = "/list2", method = RequestMethod.GET)
	List<Student> list2Student(Long id) {
		return firstPageService.nativeQuery(id);
	}

	// 分页查询
	@RequestMapping(value = "/pageRequest", method = RequestMethod.GET)
	List<Student> pageRequest() {

		return firstPageService.pageRequest();
	}

	// 分页与排序查询
	@RequestMapping(value = "/pageAndSortRequest", method = RequestMethod.GET)
	List<Student> pageAndSortRequest() {

		return firstPageService.pageAndSortRequest();
	}

四、服务层firstPageService代码如下:

@Resource
	private StudentMapper studentMapper;

	public String getString() {

		// return name;
		// int a = studentMapper.queryCount();
		// return a + "";
		return "Hellow World!";
	}

	public String addStudent(Student stu) {
		studentMapper.save(stu);
		return "添加成功";
	}

	public String deleteStudent(Long id) {
		studentMapper.delete(id);
		return "删除成功";
	}

	public String updateStudent(Student stu) {
		// 如果有就更新,没有就添加
		studentMapper.save(stu);
		return "更新成功";
	}

	public List<Student> listStudent() {

		return studentMapper.findAll();
	}

	public List<Student> nativeQuery(Long id) {
		return studentMapper.findAll(id);
	}

    // 分页查询 public List<Student> pageRequest() { PageRequest pageRequest = new PageRequest(1, 3); Page<Student> stuPage = studentMapper.findAll(pageRequest); List<Student> stuList = stuPage.getContent(); return stuList; }
    // 分页与排序 public List<Student> pageAndSortRequest() { Sort sort1 = new Sort(Sort.Direction.DESC, "id"); Sort sort2 = new Sort(Sort.Direction.ASC, "name"); // 把两个排序的条件取取与 Sort sort = sort1.and(sort2); PageRequest pageRequest = new PageRequest(1, 2, sort); Page<Student> stuPage = studentMapper.findAll(pageRequest); List<Student> stuList = stuPage.getContent(); return stuList; }

  

通过源码的继承与实现关系可以看出,JpaRepository接口继承了PagingAndSortingRepository,QueryByExampleExecutor两个接口,PagingAndSortingRepository接口继承了CrudRepository。CrudRepository中包含了简单的数据库增,删,改,查,这四个操作还是比较简单的,下面主要介绍分页与排序;

下面的是PagingAndSortingRepository的源码:

public interface PagingAndSortingRepository extends CrudRepository {

	public abstract Iterable findAll(Sort sort);

	public abstract Page findAll(Pageable pageable);
}

这个接口提供了分页与排序的基本方法,想要实现分页查询,要实现Pageable接口,而PageRequest是该接口的一个实现类,该类的构造方法:

    // 单纯的分页
    public PageRequest(int page, int size) {
		this(page, size, null);
	}

	public transient PageRequest(int page, int size, Sort.Direction direction,
			String properties[]) {
		this(page, size, new Sort(direction, properties));
	}
      // 分页与排序,要实现Sort类
	public PageRequest(int page, int size, Sort sort) {
		super(page, size);
		this.sort = sort;
	}

 

五、按照id倒序,name顺序,查询第二页,每页显示两个的查询结果:

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