深入理解Mybatis分页插件使用方法

<dependency>
 <groupId>com.github.pagehelper</groupId>
 <artifactId>pagehelper</artifactId>
 <version>最新版本</version>
</dependency>

<!--
 plugins在配置文件中的位置必须符合要求，否则会报错，顺序如下:
 properties?, settings?,
 typeAliases?, typeHandlers?,
 objectFactory?,objectWrapperFactory?,
 plugins?,
 environments?, databaseIdProvider?, mappers?
-->
<plugins>
  <plugin interceptor="com.github.pagehelper.PageHelper">
   <property name="dialect" value="mysql"/>
   <!-- 该参数默认为false -->
   <!-- 设置为true时，会将RowBounds第一个参数offset当成pageNum页码使用 -->
   <!-- 和startPage中的pageNum效果一样-->
   <property name="offsetAsPageNum" value="true"/>
   <!-- 该参数默认为false -->
   <!-- 设置为true时，使用RowBounds分页会进行count查询 -->
   <property name="rowBoundsWithCount" value="true"/>
   <!-- 设置为true时，如果pageSize=0或者RowBounds.limit = 0就会查询出全部的结果 -->
   <!-- （相当于没有执行分页查询，但是返回结果仍然是Page类型）-->
   <property name="pageSizeZero" value="true"/>
   <!-- 3.3.0版本可用 - 分页参数合理化，默认false禁用 -->
   <!-- 启用合理化时，如果pageNum<1会查询第一页，如果pageNum>pages会查询最后一页 -->
   <!-- 禁用合理化时，如果pageNum<1或pageNum>pages会返回空数据 -->
   <property name="reasonable" value="false"/>
   <!-- 3.5.0版本可用 - 为了支持startPage(Object params)方法 -->
   <!-- 增加了一个`params`参数来配置参数映射，用于从Map或ServletRequest中取值 -->
   <!-- 可以配置pageNum,pageSize,count,pageSizeZero,reasonable,不配置映射的用默认值 -->
   <!-- 不理解该含义的前提下，不要随便复制该配置 -->
   <property name="params" value="pageNum=start;pageSize=limit;"/>
  </plugin>
</plugins>

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
 <!-- 注意其他配置 -->
 <property name="plugins">
 <array>
  <bean class="com.github.pagehelper.PageInterceptor">
  <property name="properties">
   <!--使用下面的方式配置参数，一行配置一个 -->
   <value>
   params=value1
   </value>
  </property>
  </bean>
 </array>
 </property>
</bean>

public class BaseRequest implements Serializable {

 private static final long serialVersionUID = 1193444819529643410L;

 private Integer pageNum;//页数
 private Integer pageSize;//每页行数
 private Boolean count;//是否查询总条数

 public Integer getPageNum() {
  return pageNum;
 }

 public void setPageNum(Integer pageNum) {
  this.pageNum = pageNum;
 }

 public Integer getPageSize() {
  return pageSize;
 }

 public void setPageSize(Integer pageSize) {
  this.pageSize = pageSize;
 }

 public Boolean getCount() {
  return count;
 }

 public void setCount(Boolean count) {
  this.count = count;
 }

 @Override
 public String toString() {
  return "BaseRequest{" +
    "pageNum=" + pageNum +
    ", pageSize=" + pageSize +
    '}';
 }
}

public interface PageService {

 default void setDefaultPageInfo(BaseRequest baseRequest) {
  if (null != baseRequest) {
   baseRequest.setPageNum(null == baseRequest.getPageNum() ? Constants.PAGE_NUM : baseRequest.getPageNum());
   baseRequest
     .setPageSize(null == baseRequest.getPageSize() ? Constants.PAGE_SIZE : baseRequest.getPageSize());
   baseRequest.setCount(null == baseRequest.getCount() ? Boolean.TRUE : baseRequest.getCount());
  } else {
   baseRequest = new BaseRequest();
   baseRequest.setPageNum(Constants.PAGE_NUM);
   baseRequest.setPageSize(Constants.PAGE_SIZE);
   baseRequest.setCount(Boolean.TRUE);
  }
  PageHelper.startPage(baseRequest.getPageNum(), baseRequest.getPageSize(),baseRequest.getCount());
 }

}

public class PageUtils {

 public static void copyProperties(PageInfo<?> source, PageInfo<?> des) {
  des.setEndRow(source.getEndRow());
  des.setFirstPage(source.getFirstPage());
  des.setHasNextPage(source.isHasNextPage());
  des.setHasPreviousPage(source.isHasPreviousPage());
  des.setIsFirstPage(source.isIsFirstPage());
  des.setIsLastPage(source.isIsLastPage());
  des.setNavigatepageNums(source.getNavigatepageNums());
  des.setNavigatePages(source.getNavigatePages());
  des.setNextPage(source.getNextPage());
  des.setOrderBy(source.getOrderBy());
  des.setPageNum(source.getPageNum());
  des.setPages(source.getPages());
  des.setPageSize(source.getPageSize());
  des.setPrePage(source.getPrePage());
  des.setSize(source.getSize());
  des.setStartRow(source.getStartRow());
  des.setTotal(source.getTotal());
 }
}

import com.github.pagehelper.PageInfo;
import com.javxuan.common.util.PageUtils;
import com.javxuan.order.entity.Order;
import com.javxuan.order.response.OrderDto;
import com.javxuan.order.service.PageService;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.ArrayList;

public class OrderServcieImpl implements IOrderServcie, PageService {

 @Autowired
 IOrderMapper orderMapper;

 @GetMapping("/order")
 public PageInfo<OrderDto> list(OrderRequest orderRequest){
  //设置默认分页信息 PageService的方法
  setDefaultPageInfo(orderRequest);

  //查出order列表
  List<Order> orderList = orderMapper.selectList();
  //将entity的列表分页
  PageInfo<Order> orderPageInfo = new PageInfo<>(orderList);

  //连续显示5页与上面的二选一
  //PageInfo<Order> orderPageInfo = new PageInfo<>(orderList，5);

  //定义一个数据传输对象dtoList
  List<OrderDto> dtoList = new ArrayList<>();
  if(null==orderList || orderList.size<=0){
   return null;
  }

  //给dtoList 加值
  for(Order order:orderList){
   OrderDto dto = new OrderDto();
   //将entity 的属性值 复制给dto上
   BeanUtils.copyProperties(order, dto);
   dtoList.add(dto);
  }

  //给dto 分页
  PageInfo<OrderDto> dtoPageInfo = new PageInfo<>(dtoList);

  //连续显示5页 与上面的二选一
  //PageInfo<Order> orderPageInfo = new PageInfo<>(orderList，5);

  //将entity的分页信息复制给dtoPageInfo上
  PageUtils.copyProperties(orderPageInfo, dtoPageInfo);
  return dtoPageInfo;
 }
}