spring boot中实现手动分页

手动分页

1. UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="cn.mayanan.restapi.mapper.UserMapper"><!-- 在复杂的sql查询中，使用resultMap是最佳实践, 它能清晰的定义嵌套对象的映射规则 --><resultMap id="userResultMap" type="cn.mayanan.restapi.bean.UserBean"><id column="id" property="id" /><result column="name" property="username" /><result column="password" property="password" /></resultMap><!-- 查询所有用户信息 --><select id="getAllUsers" parameterType="map" resultMap="userResultMap">select id, name, password from userorder by idlimit #{pageSize}offset #{offset}</select>
</mapper>

2. UserMapper.java

package cn.mayanan.restapi.mapper;import org.apache.ibatis.annotations.Mapper;
import cn.mayanan.restapi.bean.UserBean;
import org.apache.ibatis.annotations.Param;import java.util.List;
import java.util.Map;@Mapper
public interface UserMapper {List<UserBean> getAllUsers(Map<String, Object> params);
}

3. UserService.java

package cn.mayanan.restapi.service;import cn.mayanan.restapi.bean.UserBean;import java.util.List;
import java.util.Map;public interface UserService {UserBean queryUserById(int id);List<UserBean> queryAllUser(Map<String, Object> params);
}

4. UserServiceImpl.java

package cn.mayanan.restapi.serviceImpl;import cn.mayanan.restapi.bean.UserBean;
import cn.mayanan.restapi.mapper.UserMapper;
import cn.mayanan.restapi.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;
import java.util.Map;@Service
public class UserServiceImpl implements UserService {// 将Dao注入Service层private final UserMapper userMapper;@Autowiredpublic UserServiceImpl(UserMapper userMapper) {this.userMapper = userMapper;}// 查询所有用户信息@Overridepublic List<UserBean> queryAllUser(Map<String, Object> params) {return userMapper.getAllUsers(params);}
}

5. UserController.java

package cn.mayanan.restapi.controller;import cn.mayanan.restapi.bean.UserBean;
import cn.mayanan.restapi.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;import java.util.HashMap;
import java.util.List;
import java.util.Map;// @RestController是一个方便的注解，它结合了@Controller和@ResponseBody注解
@RestController  // 标注为Rest控制器
@RequestMapping("/api")  // 定义基础路径
public class MyRestController {// 将Service注入Controller层private final UserService userService;@Autowiredpublic MyRestController(UserService userService) {this.userService = userService;}// 查询所有用户信息@GetMapping("/users")public List<UserBean> showUsers(@RequestParam(value = "pageSize", defaultValue = "1") int pageSize,@RequestParam(value = "pageNum", defaultValue = "1") int pageNum) {System.out.println("pageSize: " + pageSize + ", pageNum: " + pageNum);// 手动分页Map<String, Object> map = new HashMap<>();int offset = (pageNum - 1) * pageSize;map.put("pageSize", pageSize);map.put("offset", offset);return userService.queryAllUser(map);}
}