分页查询PageHelper插件分页条件查询（xml映射文件，动态SQL）

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黑马程序员JavaWeb开发教程

一、分页查询-分析

• 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

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 {@Autowiredprivate 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servicePageBean pageBean = empService.page(page, pageSize);//返回结果return Result.success(pageBean);}
}

1.2 service

1. 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);
}

2. 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 {@Autowiredprivate EmpMapper empMapper;/*** 分页查询** @return*/@Overridepublic 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

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 {@Autowiredprivate EmpMapper empMapper;/*** 分页查询** @return*/@Overridepublic 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 PageBeanPageBean pageBean = new PageBean(count,result);return pageBean;}
}

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

select * from emp
wherename like concat('%','张','%')and gender=1and 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

1. 同包同名
   
2. 去mybatis中文网复制配置信息，就是下边的

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//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>

3. 创建动态SQL

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//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 {@Autowiredprivate 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servicePageBean pageBean = empService.page(name, gender, begin, end, page, pageSize);//返回结果return Result.success(pageBean);}
}

2.3 service

1. 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);
}

2. 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 {@Autowiredprivate EmpMapper empMapper;/*** 分页查询** @return*/@Overridepublic 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 PageBeanPageBean 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);
}

2.5 postman测试接口

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