MyBatis拦截器 MyBatis拦截器实现分页功能的实现方法

/**
 * 分页对应的实体类
 */
public class Page {
  /**
   * 总条数
   */
  private int totalNumber;
  /**
   * 当前第几页
   */
  private int currentPage;
  /**
   * 总页数
   */
  private int totalPage;
  /**
   * 每页显示条数
   */
  private int pageNumber = 5;
  /**
   * 数据库中limit的参数，从第几条开始取
   */
  private int dbIndex;
  /**
   * 数据库中limit的参数，一共取多少条
   */
  private int dbNumber;

  /**
   * 根据当前对象中属性值计算并设置相关属性值
   */
  public void count() {
    // 计算总页数
    int totalPageTemp = this.totalNumber / this.pageNumber;
    int plus = (this.totalNumber % this.pageNumber) == 0 ? 0 : 1;
    totalPageTemp = totalPageTemp + plus;
    if(totalPageTemp <= 0) {
      totalPageTemp = 1;
    }
    this.totalPage = totalPageTemp;

    // 设置当前页数
    // 总页数小于当前页数，应将当前页数设置为总页数
    if(this.totalPage < this.currentPage) {
      this.currentPage = this.totalPage;
    }
    // 当前页数小于1设置为1
    if(this.currentPage < 1) {
      this.currentPage = 1;
    }

    // 设置limit的参数
    this.dbIndex = (this.currentPage - 1) * this.pageNumber;
    this.dbNumber = this.pageNumber;
  }

  public int getTotalNumber() {
    return totalNumber;
  }

  public void setTotalNumber(int totalNumber) {
    this.totalNumber = totalNumber;
    this.count();
  }

  public int getCurrentPage() {
    return currentPage;
  }

  public void setCurrentPage(int currentPage) {
    this.currentPage = currentPage;
  }

  public int getTotalPage() {
    return totalPage;
  }

  public void setTotalPage(int totalPage) {
    this.totalPage = totalPage;
  }

  public int getPageNumber() {
    return pageNumber;
  }

  public void setPageNumber(int pageNumber) {
    this.pageNumber = pageNumber;
    this.count();
  }

  public int getDbIndex() {
    return dbIndex;
  }

  public void setDbIndex(int dbIndex) {
    this.dbIndex = dbIndex;
  }

  public int getDbNumber() {
    return dbNumber;
  }

  public void setDbNumber(int dbNumber) {
    this.dbNumber = dbNumber;
  }
}

package com.imooc.interceptor;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Map;
import java.util.Properties;

import org.apache.ibatis.executor.parameter.ParameterHandler;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;

import com.imooc.entity.Page;

/**
 * 分页拦截器
 * 
 * @author Skye
 *
 */
@Intercepts({
    @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class, Integer.class }) })
public class PageInterceptor implements Interceptor {

  public Object intercept(Invocation invocation) throws Throwable {
    StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
    MetaObject metaObject = MetaObject.forObject(statementHandler, SystemMetaObject.DEFAULT_OBJECT_FACTORY,
        SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY, new DefaultReflectorFactory());
    MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");
    //通过MetaObject元数据取得方法名id：com.XXX.queryMessageListByPage
    String id = mappedStatement.getId();
    //匹配在mybatis中定义的与分页有关的查询id
    if (id.matches(".+ByPage$")) {
      //BoundSql中有原始的sql语句和对应的查询参数
      BoundSql boundSql = statementHandler.getBoundSql();
      Map<String, Object> params = (Map<String, Object>) boundSql.getParameterObject();
      Page page = (Page) params.get("page");
      String sql = boundSql.getSql();
      String countSql = "select count(*)from (" + sql + ")a";
      Connection connection = (Connection) invocation.getArgs()[0];
      PreparedStatement countStatement = connection.prepareStatement(countSql);
      ParameterHandler parameterHandler = (ParameterHandler) metaObject.getValue("delegate.parameterHandler");
      parameterHandler.setParameters(countStatement);
      ResultSet rs = countStatement.executeQuery();
      if (rs.next()) {
        //为什么是getInt（1）? 因为数据表的列是从1开始计数
        page.setTotalNumber(rs.getInt(1));
        System.out.println("拦截器得知page的记录总数为：" + page.getTotalNumber());
      }
      String pageSql = sql + " limit " + page.getDbIndex() + "," + page.getDbNumber();
      metaObject.setValue("delegate.boundSql.sql", pageSql);
    }
    return invocation.proceed();
  }

  /**
   * @param target
   * 被拦截的对象
   */
  public Object plugin(Object target) {
    // 如果将拦截器类比喻为代购票的公司，那this就是代购业务员（进入方法前是无代理购票能力业务员，进入后成为有代理能力的业务员）
    // 通过注解获取拦截目标的信息，如果不符合拦截要求就返回原目标，如果符合则使用动态代理生成代理对象
    return Plugin.wrap(target, this);
  }

  public void setProperties(Properties properties) {
    // TODO Auto-generated method stub

  }

}

 <!-- 自定义的分页拦截器 -->
  <plugins>
    <plugin interceptor="你写的拦截器全类名">
    </plugin>
  </plugins>

<!--pagination需要的脚本-->
<%
  // 获取请求的上下文
  String context = request.getContextPath();
%>
<link href="../css/pagination.css" rel="external nofollow" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="../js/jquery-1.11.3.js"></script>
<script type="text/javascript" src="../js/jquery.pagination.js"></script>
<script type="text/javascript">

// 点击分页按钮以后触发的动作
function handlePaginationClick(new_page_index, pagination_container) {
<!--从stuForm表单提交当前页的参数.可以使用restful方式，让springmvc使用@PathVariable关键字定义的形参去接。这2个参数是分页控件自己提供的，不需要我们去自己找，但是计数从0开始，而我们后台分页计数从1开始，因此要手动加1。 -->
  $("#stuForm").attr("action", "你定义的分页查询url/"+(new_page_index+1));
  $("#stuForm").submit();
  return false;
}

$(function(){
  $("#News-Pagination").pagination(${result.totalRecord}, {
    items_per_page:${result.pageSize}, // 每页显示多少条记录
    current_page:${result.currentPage} - 1, // 当前显示第几页数据
    num_display_entries:8, // 分页显示的条目数
    next_text:"下一页",
    prev_text:"上一页",
    num_edge_entries:2, // 连接分页主体，显示的条目数
    callback:handlePaginationClick(当前页，分页div的id), //执行的回调函数
    load_first_page:false //防止页面一直刷新( 这条非常重要！)
  });
});
</script>
<!-- 这部分用c:forEach标签打印查询结果的表格-->
<!--分页控件名称-->
<div id="News-Pagination"></div>