SpringBoot2 实现JPA分页和排序分页的案例

spring:
 datasource:
 url: jdbc:mysql://127.0.0.1/jpa?useUnicode=true&characterEncoding=utf-8&useSSL=false
 username: root
 password: 123456
 driver-class-name: com.mysql.jdbc.Driver
 jpa:
 hibernate:
 # 更新或者创建数据表结构
  ddl-auto: update
 # 控制台显示SQL
 show-sql: true
 properties:
  hibernate.format_sql: true

@Entity
@Table(name = "employee")
public class Employee {
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer empId;
 private String lastName;
 private String email;
 @Temporal(TemporalType.DATE)
 private Date birth;
 @Temporal(TemporalType.TIMESTAMP)
 private Date createTime;
 @ManyToOne
 @JoinColumn(name = "dept_id")
 private Department department;
 // 省去 set get方法
}
@Entity
@Table(name = "department")
public class Department {
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer deptId;
 private String deptName;
 // 省去 set get方法
}

import com.springboot.jpa.entity.Employee;
import org.springframework.data.jpa.repository.JpaRepository;
public interface EmployeeRepository extends JpaRepository<Employee, Integer> {
}

import com.springboot.jpa.entity.Employee;
import org.springframework.data.domain.Page;
public interface EmployeeService {
 // 普通分页
 Page<Employee> getPage(Integer pageNum, Integer pageLimit);
 // 排序分页
 Page<Employee> getPageSort(Integer pageNum, Integer pageLimit);
}

import com.springboot.jpa.dao.EmployeeRepository;
import com.springboot.jpa.entity.Employee;
import com.springboot.jpa.service.EmployeeService;
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.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
@Service
public class EmployeeServiceImpl implements EmployeeService {
 @Autowired
 private EmployeeRepository employeeRepository;
 // 普通分页
 @Override
 @Transactional(readOnly = true) // 只读事务
 public Page<Employee> getPage(Integer pageNum, Integer pageLimit) {
  Pageable pageable =new PageRequest(pageNum - 1,pageLimit);
  return employeeRepository.findAll(pageable);
 }
 // 分页排序
 @Override
 @Transactional(readOnly = true) 
 public Page<Employee> getPageSort(Integer pageNum, Integer pageLimit) {
  Sort sort = new Sort(Sort.Direction.DESC,"createTime");
  Pageable pageable =new PageRequest(pageNum - 1, pageLimit, sort);
  return employeeRepository.findAll(pageable);
 }
}

import com.springboot.jpa.entity.Employee;
import com.springboot.jpa.service.EmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class EmployeeController {
 @Autowired
 private EmployeeService employeeService;
 // 分页显示数据
 @GetMapping("/emp")
 public Page<Employee> showPage(@RequestParam(value = "page") Integer page, @RequestParam(value = "size") Integer size){
  System.out.println("分页： page:"+page+"; size:"+size);
  return employeeService.getPage(page, size);
 }
 // 排序分页显示数据
 @GetMapping("/emp_sort")
 public Page<Employee> showSortPage(@RequestParam(value = "page") Integer page, @RequestParam(value = "size") Integer size){
  System.out.println("排序分页： page:"+page+"; size:"+size);
  return employeeService.getPageSort(page, size);
 }
}

{
 "content": [{
  "lastName": "7QW",
  "email": "453@qq.com",
  "birth": "2018-08-06",
  "createTime": "2018-08-30T07:40:34.000+0000",
  "id": 5,
  "dempartment": {
   "deptName": "BBB",
   "id": 2
  }
 }, {
  "lastName": "qax",
  "email": "1223@qq.com",
  "birth": "2018-08-06",
  "createTime": "2018-08-24T07:40:56.000+0000",
  "id": 6,
  "dempartment": {
   "deptName": "AAA",
   "id": 1
  }
 }
 }],
 "pageable": {
  "sort": {
   "sorted": true,
   "unsorted": false
  },
  "offset": 0,
  "pageNumber": 0,
  "pageSize": 10,
  "unpaged": false,
  "paged": true
 },
 "last": true,
 "totalElements": 6,
 "totalPages": 1,
 "number": 0,
 "size": 10,
 "sort": {
  "sorted": true,
  "unsorted": false
 },
 "numberOfElements": 6,
 "first": true
}

@Entity
@Table(name = "user")
public class User {
@Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer id;
 @Column
 private String userName;
 @Column
 private String password;
 @Column
 private String age；
 //省略get、set
 ｝

//jpa简单分页
Page<User> getPage(Integer pageNum,Integer pageSize);

@Override
 public Page<User> getPage(Integer pageNum, Integer pageSize) {
  /**
  *之前看到别的博主直接new PageRequest(pageNum-1，pageSize)
  *自己实践后报错，可能是因为版本不一致吧 
  *查看PageRequest的底层构造方法并没有对应的只有of方法对应
  *后经实验成功！
  */
  //创建一个pageable，调用它的实现类PageRequest的of()方法
  Pageable pageable = PageRequest.of(pageNum - 1, pageSize);
  
  Page<User> userPage = userDao.findAll(pageable);
  return userPage;
 }

@Test
 void testGetPage(){
  //调用service层的getPage()方法
  Page<User> userPage = userService.getPage(1, 5);
  /**
   * userPage.getContent()
   * getContent(); 获取查询的结果集
   * Page<Object>常用方法
   * List<T> getContent(); 将所有数据返回为List
   * long getTotalElements();返回元素总数
   * int getTotalPages(); 返回分页总数
   */
  List<User> users = userPage.getContent();
  for (User user : users) {
   System.out.println(user);
  }
 }

User{id=17, userName=‘大锤', password=‘1***3', age=23}
User{id=18, userName=‘小黑', password=‘w***w', age=21}
User{id=19, userName=‘小白', password=‘2***1', age=29}
User{id=20, userName=‘小红', password=‘4***2', age=19}
User{id=21, userName=‘小芳', password=‘2***3', age=17}

@Override
 public Page<User> getPage(Integer pageNum, Integer pageSize) {
  //普通查询跟排序查询的唯一区别在于Sort
  //排序方式，这里的by()方法跟上面的那个of()方法作用差不多
  //Sort.Direction.DESC： 倒序
  //Sort.Direction.ASC ：默认升序
  //Sort.by(Sort.Direction.***, "实体类中的字段");
  //根据实体类中的字段进行排序（我使用的"age"）
  Sort sort = Sort.by(Sort.Direction.DESC, "age");
  
  //创建一个pageable，调用它的实现类PageRequest的of()方法
  //将sort加入到of()中排序完成
  Pageable pageable = PageRequest.of(pageNum - 1, pageSize,sort);
  
  Page<User> userPage = userDao.findAll(pageable);
  return userPage;
 }

User{id=19, name=‘小白', password=‘2***1', age=29}
User{id=16, name=‘老李', password=‘8***7', age=25}
User{id=17, name=‘大锤', password=‘1***3', age=23}
User{id=15, name=‘老宋', password=‘9***0', age=22}
User{id=18, name=‘小黑', password=‘w***w', age=21}