分页查询PageHelper插件分页条件查询（xml映射文件，动态SQL）

黑马程序员JavaWeb开发教程

文章目录

一、分页查询-分析
二、分页查询-实现
- 1. 实现思路
- - 1.1 controller
  - 1.2 service
  - 1.3 mapper
- 1.4 postman测试接口
三、分页查询-PageHelper插件
- 1. 引入pageHelper插件的依赖
- 2. 修改原来的代码
- - 2.1 mapper
  - 2.2 serviceimpl
  - 2.3 postman测试接口
四、分页查询-条件查询
- 1. 首先根据分页查询的需求写出查询的SQL语句
- 2. 创建动态SQL
- - 2.1 创建xml映射文件
  - 2.2 controller
  - 2.3 service
  - 2.4 mapper
  - 2.5 postman测试接口

一、分页查询-分析

在这里插入图片描述

实体类PageBean

package com.itheima.mytlias.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class PageBean {
    private Long total;//总记录数
    private List rows;//当前页的数据
}

二、分页查询-实现

1. 实现思路

请求参数：页码、每页展示记录数
响应结果：总记录数、结果列表

在这里插入图片描述

1.1 controller

package com.itheima.mytlias.controller;

import com.itheima.mytlias.pojo.PageBean;
import com.itheima.mytlias.pojo.Result;
import com.itheima.mytlias.service.EmpService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@Slf4j
@RestController
@RequestMapping("/emps")
public class EmpController {
    @Autowired
    private EmpService empService;

    @GetMapping
    //@RequestParam：为了给形参指定默认值
    public Result page(@RequestParam(defaultValue = "1") Integer page,
                       @RequestParam(defaultValue = "2") Integer pageSize) {
        //打印日志
        //调用service
        PageBean pageBean = empService.page(page, pageSize);
        //返回结果
        return Result.success(pageBean);

    }
}

1.2 service

service

package com.itheima.mytlias.service;

import com.itheima.mytlias.pojo.PageBean;

public interface EmpService {
    /**
     * 分页查询
     * @return
     */
    PageBean page(Integer page,Integer pageSize);
}

impl

package com.itheima.mytlias.service.impl;

import com.itheima.mytlias.mapper.EmpMapper;
import com.itheima.mytlias.pojo.Emp;
import com.itheima.mytlias.pojo.PageBean;
import com.itheima.mytlias.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class EmpServiceImpl implements EmpService {
    @Autowired
    private EmpMapper empMapper;

    /**
     * 分页查询
     *
     * @return
     */
    @Override
    public PageBean page(Integer page, Integer pageSize) {
        //调用mapper进行分页查询
        //列表数据
        List<Emp> empList = empMapper.list(page, pageSize);
        //总数
        Long count = empMapper.count();
        PageBean pageBean = new PageBean(count, empList);
        return pageBean;
    }
}

1.3 mapper

package com.itheima.mytlias.mapper;

import com.itheima.mytlias.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.web.bind.annotation.PathVariable;

import java.util.List;

@Mapper
public interface EmpMapper {

    /**
     * 查询总记录数
     *
     * @return
     */
    @Select("select count(*) from emp")
    public Long count();

    /**
     * 查询本页员工列表
     *
     * @param start
     * @param pageSize
     * @return
     */
    @Select("select * from emp limit #{start},#{pageSize}")
    public List<Emp> list(@Param("start") Integer start, @Param("pageSize") Integer pageSize);
}

1.4 postman测试接口

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三、分页查询-PageHelper插件

1. 引入pageHelper插件的依赖

在pom.xml中添加以下代码

<!--        pagehelper分页插件-->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.4.2</version>
        </dependency>

2. 修改原来的代码

除了EmpMapper和EmpServiceImpl中的代码意外不用修改其他的代码

2.1 mapper

package com.itheima.mytlias.mapper;

import com.itheima.mytlias.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.web.bind.annotation.PathVariable;

import java.util.List;

@Mapper
public interface EmpMapper {
    /**
     * 使用pageHelper的话，只需要定义一个简单的查询就可以
     * @return
     */
    @Select("select * from emp")
    public List<Emp> list();
}

2.2 serviceimpl

package com.itheima.mytlias.service.impl;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.itheima.mytlias.mapper.EmpMapper;
import com.itheima.mytlias.pojo.Emp;
import com.itheima.mytlias.pojo.PageBean;
import com.itheima.mytlias.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class EmpServiceImpl implements EmpService {
    @Autowired
    private EmpMapper empMapper;

    /**
     * 分页查询
     *
     * @return
     */
    @Override
    public PageBean page(Integer page, Integer pageSize) {

        //使用pagehelper指定查询页码，和每页查询数据
        PageHelper.startPage(page,pageSize);
        //执行查询
        List<Emp> empList = empMapper.list();
        Page<Emp> p= (Page<Emp>)empList;//强制转换成Page类型
        Long count=p.getTotal();
        List<Emp> result = p.getResult();
        //封装为 PageBean
        PageBean pageBean = new PageBean(count,result);
        return pageBean;
    }
}

2.3 postman测试接口

在这里插入图片描述

四、分页查询-条件查询

1. 首先根据分页查询的需求写出查询的SQL语句

select * from emp
where
    name like concat('%','张','%')
    and gender=1
    and entrydate between '2000-01-01' and '2010-01-01'
order by update_time desc;

2. 创建动态SQL

2.1 创建xml映射文件

同包同名
去mybatis中文网复制配置信息，就是下边的

<?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：EmpMapper的全类名-->
<mapper namespace="org.mybatis.example.BlogMapper">
 <!--    id：与方法名一致
            resultType：返回单条记录的全类名-->
  <select id="selectBlog" resultType="Blog">
    select * from Blog where id = #{id}
  </select>
</mapper>

创建动态SQL

<?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：EmpMapper的全类名-->
<mapper namespace="com.itheima.mytlias.mapper.EmpMapper">

    <!--    带条件的分页查询-动态查询-->
    <!--    id：与方法名一致
            resultType：返回单条记录的全类名-->
    <select id="list" resultType="com.itheima.mytlias.pojo.Emp">
        select * from emp
        <where>
            <if test="name!=null">name like concat('%',#{name},'%')</if>
            <if test="gender!=null">and gender=#{gender}</if>
            <if test="begin!=null and end!=null">and entrydate between #{begin} and #{end}</if>
        </where>
        order by update_time desc
    </select>
</mapper>

2.2 controller

package com.itheima.mytlias.controller;

import com.itheima.mytlias.pojo.PageBean;
import com.itheima.mytlias.pojo.Result;
import com.itheima.mytlias.service.EmpService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.format.annotation.DateTimeFormat;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.time.LocalDate;

@Slf4j
@RestController
@RequestMapping("/emps")
public class EmpController {
    @Autowired
    private EmpService empService;

    @GetMapping
    //@RequestParam：为了给形参指定默认值
    //@DateTimeFormat：日期时间类型的参数，需要使用该注解指定格式
    public Result page(String name, Short gender,
                       @DateTimeFormat(pattern = "yyyy-MM-dd") LocalDate begin,
                       @DateTimeFormat(pattern = "yyyy-MM-dd") LocalDate end,
                       @RequestParam(defaultValue = "1") Integer page,
                       @RequestParam(defaultValue = "2") Integer pageSize) {
        //打印日志
        log.info("参数 {},{},{},{},{},{}", name, gender, begin, end, page, pageSize);
        //调用service
        PageBean pageBean = empService.page(name, gender, begin, end, page, pageSize);
        //返回结果
        return Result.success(pageBean);

    }
}

2.3 service

service

package com.itheima.mytlias.service;

import com.itheima.mytlias.pojo.PageBean;

import java.time.LocalDate;

public interface EmpService {
    /**
     * 分页查询
     *
     * @return
     */
    PageBean page(String name, Short gender, LocalDate begin, LocalDate end, Integer page, Integer pageSize);
}

impl

package com.itheima.mytlias.service.impl;

import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.itheima.mytlias.mapper.EmpMapper;
import com.itheima.mytlias.pojo.Emp;
import com.itheima.mytlias.pojo.PageBean;
import com.itheima.mytlias.service.EmpService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.time.LocalDate;
import java.util.List;

@Service
public class EmpServiceImpl implements EmpService {
    @Autowired
    private EmpMapper empMapper;

    /**
     * 分页查询
     *
     * @return
     */
    @Override
    public PageBean page(String name, Short gender, LocalDate begin, LocalDate end, Integer page, Integer pageSize) {

        //使用pagehelper指定查询页码，和每页查询数据
        PageHelper.startPage(page, pageSize);
        //执行查询
        List<Emp> empList = empMapper.list(name, gender, begin, end);
        Page<Emp> p = (Page<Emp>) empList;//强制转换成Page类型
        Long count = p.getTotal();
        List<Emp> result = p.getResult();
        //封装为 PageBean
        PageBean pageBean = new PageBean(count, result);
        return pageBean;
    }
}

2.4 mapper

package com.itheima.mytlias.mapper;

import com.itheima.mytlias.pojo.Emp;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import org.springframework.web.bind.annotation.PathVariable;

import java.time.LocalDate;
import java.util.List;

@Mapper
public interface EmpMapper {
    /**
     * 使用pageHelper的话，只需要定义一个简单的查询就可以
     *
     * @return
     */
//    @Select("select * from emp")
    public List<Emp> list(@Param("name") String name, @Param("gender") Short gender, @Param("begin") LocalDate begin, @Param("end") LocalDate end);
}