mybatis-plus分别使用

一、PageHelper插件分页使用

准备1：引入PageHelper依赖

			<!-- pagehelper 分页插件 --><dependency><groupId>com.github.pagehelper</groupId><artifactId>pagehelper-spring-boot-starter</artifactId><version>1.4.6</version></dependency>

准备2：新建表格分页数据对象

import lombok.Data;
import java.io.Serializable;
import java.util.List;/*** 表格分页数据对象*/
@Data
public class TableDataInfo implements Serializable
{private static final long serialVersionUID = 1L;/** 总记录数 */private long total;/** 列表数据 */private List<?> rows;/** 消息状态码 */private int code;/** 消息内容 */private String msg;
}

准备3：分页数据类

import lombok.Data;/*** 分页数据*/
@Data
public class PageDomain
{/** 当前记录起始索引 */private Integer pageNum;/** 每页显示记录数 */private Integer pageSize;/** 排序列 */private String orderByColumn;/** 排序的方向desc或者asc */private String isAsc = "asc";/** 分页参数合理化 */private Boolean reasonable = true;public String getOrderBy(){if (StringUtils.isEmpty(orderByColumn)){return "";}return StringUtils.toUnderScoreCase(orderByColumn) + " " + isAsc;}public String getIsAsc(){return isAsc;}public void setIsAsc(String isAsc){if (StringUtils.isNotEmpty(isAsc)){// 兼容前端排序类型if ("ascending".equals(isAsc)){isAsc = "asc";}else if ("descending".equals(isAsc)){isAsc = "desc";}this.isAsc = isAsc;}}public Boolean getReasonable(){if (StringUtils.isNull(reasonable)){return Boolean.TRUE;}return reasonable;}public void setReasonable(Boolean reasonable){this.reasonable = reasonable;}
}

准备4：分页工具类

/*** 分页工具类*/
public class PageUtils extends PageHelper
{/*** 设置请求分页数据*/public static void startPage(){PageDomain pageDomain = TableSupport.buildPageRequest();Integer pageNum = pageDomain.getPageNum();Integer pageSize = pageDomain.getPageSize();String orderBy = SqlUtil.escapeOrderBySql(pageDomain.getOrderBy());Boolean reasonable = pageDomain.getReasonable();PageHelper.startPage(pageNum, pageSize, orderBy).setReasonable(reasonable);}
}

准备5：响应请求分页数据的方法

	/*** 响应请求分页数据*/@SuppressWarnings({ "rawtypes", "unchecked" })public TableDataInfo getDataTable(List<?> list){TableDataInfo rspData = new TableDataInfo();rspData.setCode(HttpStatus.SUCCESS);rspData.setMsg("查询成功");rspData.setRows(list);rspData.setTotal(new PageInfo(list).getTotal());return rspData;}

正式使用

1、如果只是单表查询，可以用QueryWrapper

controller层

	@GetMapping("/list")public TableDataInfo list(Student s){PageUtils.startPage();List<Student> list = StudentService.selectStudentList(s);return getDataTable(list);}

在service层新增接口以及实现类的方法

List<Student> selectStudentList(Student s);

	@Overridepublic List<Student> selectStudentList(Student s) {QueryWrapper<Student> queryWrapper = new QueryWrapper<>();// 所有待查询的条件if (null != s.getId()) {queryWrapper.lambda().eq(Student::getId, Student.getId());}if (StringUtils.isNotEmpty(s.getStudentName())) {queryWrapper.lambda().like(Student::getStudentName, s.getStudentName());}return kaddOrInfoMapper.selectList(queryWrapper);}

2、或者自定义SQL要多表查询，可以自己写方法联表查询

controller层

	@GetMapping("/list")public TableDataInfo list(Student s){PageUtils.startPage();List<Student> list = StudentService.selectStudentList(s);return getDataTable(list);}

service层忽略，就去调Mapper层方法就行
Mapper接口

List<Student> selectStudentList(Student s);

Mapper.xml

<select id="selectStudentList" resultType="com.StudentDTO">SELECTc.*,s.*FROMclassroom cLEFT JOIN student s ON student.id = classroom.student_id<where><if test="id != null and id != ''">AND s.id = #{id}</if><if test="studentName != null and studentName != ''">AND s.bu like concat('%', #{studentName}, '%')</if>
<!--            <if test="beginTime != null and beginTime != ''">&lt;!&ndash; 开始时间检索 &ndash;&gt;-->
<!--                and date_format(create_time,'%y%m%d') &gt;= date_format(#{beginTime},'%y%m%d')-->
<!--            </if>-->
<!--            <if test="endTime != null and endTime != ''">&lt;!&ndash; 结束时间检索 &ndash;&gt;-->
<!--                and date_format(create_time,'%y%m%d') &lt;= date_format(#{endTime},'%y%m%d')-->
<!--            </if>--></where></select>

二、使用Mybatis-plus自带分页Ipage进行分页

不需要准备，直接正式使用

1、如果只是单表查询，可以用QueryWrapper

controller层

	@GetMapping(value = "/listPage")public IPage findListByPage(StudentQO studentQO) {return studentService.queryPageList(studentQO);}

设置查询参数

	/*** 设置查询参数* @return*/private QueryWrapper<Student> getQueryParam(StudentQO studentQO) {QueryWrapper<KaddPoaOrMatch> queryWrapper = new QueryWrapper<>();// 所有待查询的条件if (studentQO.getId() != null) {queryWrapper.lambda().eq(Student::getId, studentQO.getId());}if (studentQO.getStudentName() != null) {queryWrapper.lambda().like(Student::getStudentName, studentQO.getStudentName());}return queryWrapper;}

service层

@Overridepublic IPage queryPageList(StudentQO studentQO) {IPage<StudentQO> page = new Page<>(studentQO.getPageNum(),studentQO.getPageSize());IPage<StudentQO> iPage = studentMapper.selectPage(page, getQueryParam(studentQO));return iPage;}

2、或者自定义SQL要多表查询，可以自己写方法联表查询

controller层一样

	@GetMapping(value = "/listPage")public IPage findListByPage(StudentQO studentQO) {return studentService.queryPageList(studentQO);}

service层

@Overridepublic IPage queryPageList(StudentQO studentQO) {IPage<StudentQO> page = new Page<>(studentQO.getPageNum(),studentQO.getPageSize());IPage<StudentQO> iPage = studentMapper.selectStudentList(page, studentQO);return iPage;}

Mapper接口

IPage<StudentQO> selectStudentList(@Param("iPage") IPage<StudentQO> iPage, @Param("param") StudentQO studentQO);

Mapper.xml

<select id="selectStudentList" resultType="com.StudentDTO">SELECTc.*,s.*FROMclassroom cLEFT JOIN student s ON student.id = classroom.student_id<where><if test="param.id != null and param.id != ''">AND s.id = #{param.id}</if><if test="param.studentName != null and param.studentName != ''">AND s.bu like concat('%', #{param.studentName}, '%')</if></where></select>

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