实现flex的分页查询需要去维护一个对应的获取数据库总数的方法，下面会对有无该方法进行一个比较
实现文件主要以下几个类，注意UserMapper.xml的位置，默认是扫描resources下的mapper包
首先实现UserService和对应的实现类，并在内部进行对应逻辑代码实现
UserService
public interface IUserService {
List<User> getAll();
/**
*
* @param page 当前页数
* @param pageSize 每页的总条数
* @return
*/
Page<User> getPage(int page, int pageSize);
}
UserServiceImpl 对应的实现类
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements IUserService {
@Resource
private UserMapper userMapper;
@Override
public List<User> getAll() {
return this.getMapper().selectAll();
}
@Override
public Page<User> getPage(int page, int pageSize) {
// 查询数据库的条件 这边可以根据自身需求进行对应条件添加
// 可以自行查看源码，这边不加以阐述
QueryWrapper queryWrapper = QueryWrapper.create();
// selectPage 对应的指定mapper的方法
// page.of()内的page 和 pageSize就对应我们的参数 即页数和行数
// queryWrapper 查询条件
Page<User> pageInfo = userMapper.xmlPaginate("selectPage", Page.of(page, pageSize) , queryWrapper);
return pageInfo;
}
}
Mapper
@Mapper
public interface UserMapper extends BaseMapper<User> {
/**
* flex的分页配置
* @return
*/
long selectPage_COUNT();
/**
* 分页
* @return
*/
List<User> selectPage();
}
Mapper.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" >
<!--namespace根据自己需要创建的的mapper的路径和名称填写-->
<mapper namespace="org.wyq.studyone.mapper.UserMapper">
<!-- 分页查询-->
<!-- resultType对应的是你的实体类 User的路径-->
<select id="selectPage" resultType="org.wyq.studyone.entity.User">
select *
from `user` limit ${pageOffset}, ${pageSize}
</select>
<!-- flex分页配置-->
<select id="selectPage_COUNT" resultType="long">
select count(*)
from `user`
</select>
</mapper>
selectPage_COUNT该方法没有的话在执行分页方法时会报错，具体如下
java.lang.IllegalArgumentException: Mapped Statements collection does not contain value for org.wyq.studyone.mapper.UserMapper.selectPage_COUNT
可以看到，在没有selectPage_COUNT的情况下，会报找不到这个方法，可我们明明没有调用过该函数啊，其实这个是分页的内部会去进行的一个调用，对此我们可以看一下xmlPaginate相关的源码
Page<User> pageInfo = userMapper.xmlPaginate("selectPage", Page.of(page, pageSize) , queryWrapper);
default <E> Page<E> xmlPaginate(String dataSelectId, Page<E> page, QueryWrapper queryWrapper) {
return this.xmlPaginate(dataSelectId, dataSelectId + "_COUNT", page, queryWrapper, (Map)null);
}
可以看到，其内部的组装了 dataSelectId + "_COUNT" 这吗一个变量，这个变量其实就是selectPage + _COUNT 也就是 selectPage_COUNT，所以我们以后要写分页代码的话就需要加个对应的 dataSelectId + "_COUNT" 用来实现其分页内部的变量
这个虽然麻烦但一定意义上实现了代码的更加灵活性
好了，开始代码测试
controller层：
/*
* Copyright 2013-2018 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.wyq.studyone.controller;
import com.mybatisflex.core.paginate.Page;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.wyq.studyone.entity.User;
import org.wyq.studyone.service.IUserService;
import javax.annotation.Resource;
import java.util.List;
/**
* @author <a href="mailto:chenxilzx1@gmail.com" rel="external nofollow" >theonefx</a>
*/
@Controller
public class UserController {
@Resource
private IUserService userService;
@RequestMapping("/hello")
@ResponseBody
public String hello() {
List<User> all = userService.getAll();
return all.toString();
}
@RequestMapping("/page")
@ResponseBody
public String page(int page, int pageSize) {
Page<User> pageInfo = userService.getPage(page, pageSize);
return pageInfo.toString();
}
}
可以看到确实是获取前面五条数据
