Mybatis分页实现

一、引言

Mybatis提供了强大的分页拦截实现，可以完美的实现分功能

二、普通的分页实现

普通分页实现即使直接在mapper文件中写分页查询语句

Messsage.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.imooc.bean.Message"><resultMap type="com.imooc.bean.Message" id="MessageResult"><id column="id" jdbcType="INTEGER" property="id"/><result column="command" jdbcType="VARCHAR" property="command"/><result column="description" jdbcType="VARCHAR" property="description"/><result column="content" jdbcType="VARCHAR" property="content"/></resultMap><!-- 普通分页实现       使用sql实现分页查询，不是使用拦截器 oracle分页使用rownum,子查询呢需要使用别名不能使用rownum，row等关键字--><select id="queryMessageListByPage" parameterType="java.util.Map" resultMap="MessageResult">select * from ( select rownum r, id,command,description,content from message<where><if test="command != null and command.trim() != ''">and command=#{command}</if><if test="descriptioin != null and description.trim() != '' ">and descriptioin=#{descriptioin}</if><if test="page != null">and rownum <= #{page.dbNumber}</if></where>)<where>and r > #{page.dbIndex}</where>order by id</select><select id="count" parameterType="com.imooc.bean.Message"  resultType="int">select count(*) from message<where><if test="command != null and !"".equals(command.trim())">and command=#{command}</if><if test="description != null and ''!=description.trim()">and description like concat(concat('%',#{description}),'%')</if></where></select>
</mapper>

Page.java分页相关的参数都通过该类对象设置

package com.imooc.common;/*** 分页对应的实体类*/
public class Page {/*** 总条数* */private int totalNumber;/*** 总页数* */private int totalPage;/*** 当前页* */private int currentPage;/*** 每页显示的数目* */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,适用于mysql, 如果是oracle则表示最大取到的条数* */private int dbNumber;/*** 根据当前对象中的属性值计算并设置相关属性的值* */public void count() {// 计算总页数int totalPageTemp = this.totalNumber / this.pageNumber;int plus = (this.totalNumber % this.pageNumber) == 0 ? 0 : 1;totalPageTemp += plus;// 如果总页数小于0显示第一页if (totalPageTemp <= 0) {totalPageTemp += 1;}this.totalPage = totalPageTemp;  //设置limit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;count();}public int gettotalPage() {return totalPage;}public void settotalPage(int totalPage) {this.totalPage = totalPage;}public int getCurrentPage() {return currentPage;}public void setCurrentPage(int currentPage) {this.currentPage = currentPage;count();}public int getPageNumber() {return pageNumber;}public void setPageNumber(int pageNumber) {this.pageNumber = pageNumber;}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;}}

Dao层实现

package com.imooc.dao;import java.util.HashMap;
import java.util.List;
import java.util.Map;import org.apache.ibatis.session.SqlSession;
import com.imooc.bean.Message;
import com.imooc.common.Page;
import com.imooc.db.DBAccess;public class MessageDao {DBAccess dbAccess = new DBAccess();//计算查询的数据的总数public int getMessageCount(String command,String description) throws Exception{int count = 0;SqlSession session = null;try {session = dbAccess.getSqlSession();Message message = new Message();message.setCommand(command);message.setDescription(description);count = session.selectOne(Message.class.getName()+".count", message);} catch (Exception e) {throw new Exception(e.getMessage());} finally {if (session != null) {session.close();}}return count;} //分页实现主要的方法public List<Message> queryMessageListByPage(String command, String description,Page page) throws Exception {List<Message> messagesList = null;SqlSession session = null;try {session = dbAccess.getSqlSession();Map<String, Object> paramater = new HashMap<String, Object>();paramater.put("command", command);paramater.put("description", description);paramater.put("page", page);messagesList = session.selectList(Message.class.getName()+".queryMessageListByPage2", paramater);} catch (Exception e) {e.printStackTrace();throw new Exception(e.getMessage());} finally {if (session != null) {session.close();}}return messagesList;}}

Service层实现

调用Dao层的方法，返回本次查询的数据

package com.imooc.service;import java.util.ArrayList;
import java.util.List;
import com.imooc.bean.Message;
import com.imooc.common.Page;
import com.imooc.dao.MessageDao;public class MessageService {MessageDao dao = new MessageDao();public int getCount(String command, String description) throws Exception {int count = 0;try {count= dao.getMessageCount(command, description);} catch (Exception e) {throw new Exception(e.getMessage());}return count;}public List<Message> queryMessageListByPage(String command, String description,Page page) throws Exception {List<Message> messageList = null;try {messageList = dao.queryMessageListByPage(command, description, page);} catch (Exception e) {throw new Exception(e.getMessage());}return messageList;}
}

ListServet.java

用于接收前台页面的参数，以及传回数据给jsp页面

package com.imooc.servlet;import java.io.IOException;
import java.util.List;
import java.util.regex.Pattern;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.imooc.bean.Message;
import com.imooc.common.Page;
import com.imooc.service.MessageService;public class ListServlet extends HttpServlet {/*** */private static final long serialVersionUID = 1L;MessageService messageService = new MessageService();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) {try {// 设置编码req.setCharacterEncoding("utf-8");// 接受参数String command = req.getParameter("command");String description = req.getParameter("description");String currentPage = req.getParameter("currentPage");//创建分页对象Page page = new Page();//设置总条数page.setTotalNumber(messageService.getCount(command, description));Pattern patttern = Pattern.compile("[0-9]{1,9}"); if(currentPage == null || !patttern.matcher(currentPage).matches()){page.setCurrentPage(1);}else {page.setCurrentPage(Integer.parseInt(currentPage));}//oracle数据库分页，dbNumber表示最大能取到的条数page.setDbNumber(page.getDbIndex()+page.getPageNumber());List<Message> messageList = messageService.queryMessageListByPage(command, description, page);req.setAttribute("command", command);req.setAttribute("description", description);req.setAttribute("messages", messageList);req.setAttribute("page", page);// 向页面跳转req.getRequestDispatcher("/WEB-INF/jsp/back/list.jsp").forward(req,resp);} catch (Exception e) {e.printStackTrace();req.setAttribute("retMsg", "查询失败");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {doGet(req, resp);}}

jsp页面实现

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><meta http-equiv="X-UA-Compatible"content="IE=9; IE=8; IE=7; IE=EDGE" /><title>内容列表页面</title><link href="<%= basePath %>css/all.css" rel="stylesheet" type="text/css" /><script src="<%= basePath %>js/common/jquery-1.8.0.min.js"></script><script src="<%= basePath %>js/back/list.js"></script></head><body style="background: #e1e9eb;"><form action="<%= basePath %>List.action" id="mainForm" method="post"><input type="hidden" name="currentPage" id="currentPage" value="${page.currentPage}"/><div class="right"><div class="current">当前位置：<a href="javascript:void(0)" style="color:#6E6E6E;">内容管理</a> > 内容列表</div><div class="rightCont"><p class="g_title fix">内容列表 <a class="btn03" href="#">新 增</a>    <a class="btn03" href="javascript:deleteBatch('<%=basePath%>');">删 除</a></p><table class="tab1"><tbody><tr><td width="90" align="right">指令名称：</td><td><input name="command" type="text" class="allInput" value="${command}"/></td><td width="90" align="right">描述：</td><td><input name="description" type="text" class="allInput" value="${description}"/></td><td width="85" align="right"><input type="submit" class="tabSub" value="查 询" /></td></tr></tbody></table><div class="zixun fix"><table class="tab2" width="100%"><tbody><tr><th><input type="checkbox" id="all" οnclick="javascript:selAllCheckbox('id')"/></th><th>序号</th><th>指令名称</th><th>描述</th><th>操作</th></tr><c:forEach items="${requestScope.messages}" var="message" varStatus="status"><tr  <c:if test="${status.index % 2 != 0}">style='background-color:#ECF6EE;'</c:if>><td><input type="checkbox"  name="id" value="${message.id}"/></td><td>${status.index + 1}</td><td>${message.command}</td><td>${message.description}</td><td><a href="#">修改</a>   <a href="${basePath}DeleteOneServlet.action?id=${message.id}">删除</a></td></tr></c:forEach></tbody></table><div class='page fix'>共 <b>${page.totalNumber}</b> 条共<b>${page.totalPage }</b>页<c:if test="${page.currentPage != 1}"><a href="javascript:changeCurrentPage('1')" class='first'>首页</a><a href="javascript:changeCurrentPage('${page.currentPage-1}')" class='pre'>上一页</a></c:if>当前第<span>${page.currentPage}/${page.totalPage}</span>页<c:if test="${page.currentPage != page.totalPage}"><a href="javascript:changeCurrentPage('${page.currentPage+1}')" class='next'>下一页</a><a href="javascript:changeCurrentPage('${page.totalPage}')" class='last'>末页</a></c:if>跳至 <input id="currentPageText" type='text' value='${page.currentPage}' class='allInput w28' /> 页 <a href="javascript:changeCurrentPage($('#currentPageText').val())" class='go'>GO</a></div></div></div></div></form></body>
</html>

使用jquery提交分页参数

/*
* 实现翻页功能
*/
function changeCurrentPage(currentPage){
$("#currentPage").val(currentPage).val();
$("#mainForm").submit();
}

三、使用Mybatis分页拦截器实现

使用Mybatis分页拦截器，我们可以不用在Mapper配置文件中写分页查询语句，我们只需要写非分页查询语句就行，然后通过分页拦截器，拦截到需要分页查询的普通sql

将普通的sql替换成分页sql，非常巧妙的实现分页查询

1.实现拦截器我们需实现Interceptor

我们假如将拦截器形象的比喻成够票与代理商

a.@Intercepts注解声明了代够员取哪里拦截需要买票的顾客（去哪里拦截顾客）

b.setProperties获取Configuration.xml中plugins--》plugin--->propertis中的固定资本（公司固定资本）

c.plugin方法中判断是否需要拦截（顾客是否需要购票）

d.intercept方法中可以获取原始的sql(非分页查询的sql),和分页参数通过取到这些参数替换掉原来的sql即编程分页sql(代购员从顾客哪里获取信息)

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.RoutingStatementHandler;
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.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.apache.ibatis.session.Configuration;import com.imooc.common.Page;/*** myBatis分页拦截器实现* 拦截器在配置文件Configuration.xml中注册后，通过下边的注解声明拦截的类，方法，方法参数* */
//type指向需要拦截的接口，method指向需要拦截的方法，args指向方法中的参数
//StatementHandler是一个接口，实现类是BaseStatementHanlder，实现了其中的prepare方法，实现方法中instantiateStatement(connection)
//返回Statement
@Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class})})
public class PageInterceptor implements Interceptor{private Object object;private static String defualtSqlId = ".+ByPage$";  //需要拦截的配置文件中的id的正则表达式private static String defaultDialect = "oracle";   //默认数据库类型private String dialect;                //数据库类型/*** 3.代购* 可以指定拦截映射文件中那种id的值，* invocation中可以获取想要的数据* */@Overridepublic Object intercept(Invocation invocation) throws Throwable {//代理业务员获取代理对象的携带的信息（需要买票的人哪里获取信息）StatementHandler statementHandler = (StatementHandler)invocation.getTarget();//使用metaObject中获取statementHandler属性的值MetaObject metaObject = MetaObject.forObject(statementHandler, SystemMetaObject.DEFAULT_OBJECT_FACTORY, SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY);//BaseStatementHandler-->mappedStatement(delegate为<span style="font-family: Arial, Helvetica, sans-serif;">mappedStatement属性名</span><span style="font-family: Arial, Helvetica, sans-serif;">)</span>MappedStatement mappedStatement=(MappedStatement) metaObject.getValue("delegate.mappedStatement");Configuration configuration = (Configuration) metaObject.getValue("delegate.configuration");//获取数据库类型，获取Configuration.xml properties标签中声明的变量dialect = configuration.getVariables().getProperty("dialect");if (null == dialect || "".equals(dialect)) {dialect = defaultDialect;}//获取mapper文件中sql语句的idString pageSqlId = mappedStatement.getId();if(pageSqlId.matches(defualtSqlId)){//获取已Bypage结尾的id中的sql语句           拦截谁BoundSql boundSql = statementHandler.getBoundSql();//获取原始的sqlString sql = boundSql.getSql();//查询总条数String countSql = "select count(*) from ("+sql+") a";Connection connection = (Connection) invocation.getArgs()[0];PreparedStatement countStatement = connection.prepareStatement(countSql);//获取原始的sql参数信息ParameterHandler parameterHandler =  (ParameterHandler) metaObject.getValue("delegate.parameterHandler");//设置参数值parameterHandler.setParameters(countStatement);//执行获取总条数ResultSet rs = countStatement.executeQuery();//改造成带分页查询的sql，获取传给配置文件的参数,就是MessageDao中queryMessageListByPage中方法执行中传递进去的map参数，所以需要强转Map<String, Object> parameter = (Map<String, Object>) boundSql.getParameterObject();//paramter(map)中传入的page对象的参数Page page = (Page)parameter.get("page"); //设置page的总条数if(rs.next()){page.setTotalNumber(rs.getInt(1));}//改造成带分页查询的sqlString pageSql = buildPageSql(sql,page);//替换员来的sql//第一参数：找到源码中的sql//第二个参数：改造后的sqlmetaObject.setValue("delegate.boundSql.sql", pageSql);          //买票}return invocation.proceed();   //交回主权，买票后送回}/*** 2.定位客户  @Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class})})* 如果拦截成功，会返回一个代理类（业务员），然后会执行intercept方法* 就好比拦截到买票的人，需不需要买票，不需要放行，return就是放行* 需要就代表一种协议Plugin.wrap(target, this);* target就好比拦截住的需要买票的人,this就是公司的业务员，返回后this就变成可以代理target去买票的业务员* */@Overridepublic Object plugin(Object target) {return Plugin.wrap(target, this);}/*** 1.获取固定资本* 获取Configuration.xml中的plugin中的property中的属性值* */@Overridepublic void setProperties(Properties properties) {this.object = properties.get("test"); }/*** 改造成带分页查询的sql* sql原始sql(不带分页功能)* Page page分页实体类对象**/public String buildPageSql(String sql,Page page){StringBuilder builder = new StringBuilder();if(dialect.equals("oracle")){builder = pageSqlForOracle(sql, page);}if(dialect.equals("mysql")){pageSqlForMysql(sql, page);}return builder.toString();}//mysql分页查询public StringBuilder pageSqlForMysql(String sql,Page page){StringBuilder builder = new StringBuilder();builder.append(sql);builder.append(" limit "+page.getDbIndex()+","+page.getDbNumber());builder.append(" order by id");return builder;}/*** 实现oracle分页* */public StringBuilder pageSqlForOracle(String sql,Page page){StringBuilder builder = new StringBuilder();builder.append("select * from ( select rownum r, id,command,description,content from (");builder.append(sql);builder.append(") where rownum <= ").append(page.getDbNumber()+page.getDbIndex());builder.append(") where r > ").append(page.getDbIndex());builder.append(" order by id");System.out.println(builder.toString());return builder;}
}

Configuration.xml中注册分页拦截器插件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration><properties><property name="dialect" value="oracle" /></properties><!-- 拦截器可以有很多，就像代购公司有很多每一个公司都需要注册，下边就是注册 --><plugins><plugin interceptor="com.imooc.interceptor.PageInterceptor"><property name="test" value="interceptor" /><!-- property中的值可以在拦截器中的setProperties中拿到 --></plugin></plugins><environments default="development"><environment id="development"><transactionManager type="JDBC"><property name="" value="" /></transactionManager><dataSource type="UNPOOLED"><property name="driver" value="oracle.jdbc.driver.OracleDriver" /><!-- <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl"/> --><property name="url" value="jdbc:oracle:thin:@localhost:1521:xe" /><property name="username" value="caojx" /><property name="password" value="caojx" /></dataSource></environment></environments><mappers><mapper resource="com/imooc/config/sqlxml/Message.xml" /></mappers></configuration>

Message.xml变化

不需要写分语句

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.imooc.bean.Message"><resultMap type="com.imooc.bean.Message" id="MessageResult"><id column="id" jdbcType="INTEGER" property="id"/><result column="command" jdbcType="VARCHAR" property="command"/><result column="description" jdbcType="VARCHAR" property="description"/><result column="content" jdbcType="VARCHAR" property="content"/></resultMap><!-- select标签用于书写查询语句--><select id="queryMessageListByPage" parameterType="java.util.Map" resultMap="MessageResult">select id,command,description,content from message<where><if test="command != null and !"".equals(command.trim())">and command=#{command}</if><!-- like 查询一般会拼接concat()拼接两个字符串 --><if test="description != null and ''!=description.trim()">and description like concat(concat('%',#{description}),'%')</if></where></select>
</mapper>

ListServlet.java中的一小点变化

package com.imooc.servlet;import java.io.IOException;
import java.util.List;
import java.util.regex.Pattern;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.imooc.bean.Message;
import com.imooc.common.Page;
import com.imooc.service.MessageService;public class ListServlet extends HttpServlet {/*** */private static final long serialVersionUID = 1L;MessageService messageService = new MessageService();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) {try {// 设置编码req.setCharacterEncoding("utf-8");// 接受参数String command = req.getParameter("command");String description = req.getParameter("description");String currentPage = req.getParameter("currentPage");//创建分页对象Page page = new Page();   Pattern patttern = Pattern.compile("[0-9]{1,9}"); if(currentPage == null || !patttern.matcher(currentPage).matches()){page.setCurrentPage(1);}else {page.setCurrentPage(Integer.parseInt(currentPage));}List<Message> messageList = messageService.queryMessageListByPage(command, description, page);req.setAttribute("command", command);req.setAttribute("description", description);req.setAttribute("messages", messageList);req.setAttribute("page", page);// 向页面跳转req.getRequestDispatcher("/WEB-INF/jsp/back/list.jsp").forward(req,resp);} catch (Exception e) {e.printStackTrace();req.setAttribute("retMsg", "查询失败");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {doGet(req, resp);}}

结果图

注：本案例思想有慕课网提供指导