利用Spring MVC+Mybatis实现Mysql分页数据查询的过程详解

前言

因为最近没什么事，所以想着写一个分页的例子出来给大家分享一下。这个案例分前端和后台两部分，前端使用面向对象的方式写的，里面用到了一些回调函数和事件代理，有兴趣的朋友可以研究一下。后台的实现技术是将分页Pager作为一个实体对象放到domain层，当前页、单页数据量、当前页开始数、当前页结束数、总数据条数、总页数都作为成员属性放到实体类里面。

以前项目数据库用的是oracle，sql语句的写法会从当前页开始数到当前页结束数查询数据。刚刚在这纠结了很长时间，查询到的数据显示数量总是有偏差，后来发现mysql的语句limit用的是当前页开始数到查询的条数，the fuck，我还一直以为它也是到当前页结束数呢。下面话不多说了，来一起看看详细的实现过程吧：

第一步，搭建这个小案例，引入spring和mybtis的jar包，配置对应的配置文件：

第二步，前端页面和数据的处理：

页面布局很简单。我将table和pager单独作为对象来处理，各自处理各自该干的事情，做到了很好的封装处理。个人认为这两个js和java的类很相似。

其它的地方都是按照正常分页的流程走的，话不多说，看看代码吧。　

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <style>
  .hide{display:none}
  .myPager{height:40px;border-bottom:1px solid #eee;}
 .myPager .pagerRow{width:100%;float:left;height:30px;margin-top:10px;}
 .myPager .showPage{width:100%;float:left;height:30px;margin-top:10px;text-align: left;}
 .myPager .showPage .numDiv{display:inline-block;}
 .myPager .showPage .toBtn{color:#fff;font-size:20px;}
 .myPager .showPage .disable{background-color: #c9c9c9;}
 .myPager .showPage .nable{background-color:rgb(10%,65%,85%);cursor:default;}
 .myPager .showPage .numDiv .disable{color:#777;}
 .myPager .showPage .numDiv .nable{color:#fff;}
 .myPager .showPage .cursor_default{cursor:default;}
 .myPager .showPage .cursor_pointer{cursor:pointer;}
 .showPage span{display: inline-block;padding: 0px 0px 1px 1px;margin-left:5px;
  width: 21px;height: 21px;border-radius: 12px;line-height: 22px;font-size: 12px;
  text-align: center;overflow: hidden;}
 </style>
 <script type="text/javascript" src="<c:url value='/res/jquery.js'/>"></script>
 <script type="text/javascript" src="<c:url value='/res/MyPager.js'/>"></script>
 <script type="text/javascript" src="<c:url value='/res/MyTable.js'/>"></script>
 <script>
 $(function(){
  var $btn = $(".sub_btn");
  $btn.click(function(){
  $(this).addClass("hide");
  new MyTable("employeeTab","<c:url value='/mam/queryListPage'/>");
  })
 })
 </script>
 </head>

 <body>
 <div class="wrap">
  <table class="employeeTab">
  <tr>
   <th>ID</th>
   <th>姓名</th>
   <th>年龄</th>
   <th>性别</th>
  </tr>
  </table>
  <button class="sub_btn">显示数据</button>
 </div>
 </body>
</html>

页面引入了Mypager.js和MyTable.js，Mypager这套东西是封装的比较好的，有兴趣的朋友可以直接拿去用。现在插件满天飞，自己造的轮子肯定会逊色很多，但是这里涉及到js很多基础的知识点，初学的朋友可以当做学习参考使用;

Pager.getSpan = function(value,className){
 return $("<span class='"+className+"'>"+value+"</span>");
}
function Pager($parent){
 this.$parent = $parent;
 this.pageCallBack = $.noop;
 this.preVal = "＜";
 this.nextVal = "＞";
 this.splitChar = "…";
 this.init();
 this.spaceStep = 2;
}
Pager.prototype.setPageCallBack = function(pageCallBack){
 this.pageCallBack = pageCallBack;
 return this;
}
Pager.prototype.init = function(){
 if(this.$parent.length == 0){
 alert("pagediv not exists ");
 }
 this.$divRow = $("<div class='pagerRow'></div>").appendTo(this.$parent);
 this.$div = $("<div class='showPage'>").appendTo(this.$parent);
}
Pager.prototype.clear = function(){
 this.$div.empty();
 this.$divRow.empty();
}
Pager.prototype.addSpan = function(value,className){
 var $span = Pager.getSpan(value,className).appendTo(this.$numdiv);
 $span.css("width",this.getSpanWidth(value)+"px");
 return $span;
}
Pager.prototype.getSpanWidth = function(value){
 var width = 21;
 var curNeed = 0;
 if(!isNaN(value)){
 curNeed = value.toString().length * 8;
 }
 return curNeed>width?curNeed:width;
}
Pager.prototype.disable = function($span,flag){
 var removeClass = flag?"nable cursor_pointer":"disable cursor_default";
 var addClass = flag?"disable cursor_default":"nable cursor_pointer";
 $span.removeClass(removeClass).addClass(addClass);
 return $span;
}
Pager.prototype.show = function(pageCount,curPage,rowCount){
 alert(0)
 this.clear();
 this.$divRow.html("　　共有"+pageCount+"页，"+rowCount+"条数据");
 pageCount = pageCount?pageCount-0:0;
 if(pageCount<=0){
 return;
 }
 var self = this;
 this.$prev = Pager.getSpan(this.preVal,"toBtn").appendTo(this.$div);
 this.$numdiv = $("<div class='numDiv'></div>").appendTo(this.$div);
 this.$nextVal = Pager.getSpan(this.nextVal,"toBtn").appendTo(this.$div);
 curPage = curPage?curPage-0:1;
 curPage = curPage<1?1:curPage;
 curPage = curPage>pageCount?pageCount:curPage;
 this.disable(this.$prev,curPage == 1);
 if(curPage>1){
 this.$prev.click(function(){
  self.pageCallBack(curPage-1);
  });
 }
 this.disable(this.$nextVal,curPage == pageCount);
 if(curPage<pageCount){
 this.$nextVal.click(function(){
  self.pageCallBack(curPage+1);
  });
 }
 var steps = this.getSteps(pageCount,curPage);
 for(var i in steps){
 if(i == curPage){
  this.addSpan(steps[i],"nable");
  continue;
 }
 if(steps[i] == this.splitChar){
  this.addSpan(steps[i]);
  continue;
 }

 this.addSpan(steps[i],"disable").hover($.proxy(this.mouseover,this),$.proxy(this.mouseout,this))
  .click(function(){
  alert(0)
  self.pageCallBack($(this).html());
  });
 }
}
Pager.prototype.mouseout = function(e){
 var $span = $(e.target);
 this.disable($span,true);
}
Pager.prototype.mouseover = function(e){
 var $span = $(e.target);
 this.disable($span,false);
}
Pager.prototype.getSteps = function (pageCount,curPage){
 var steps = {};
 var curStar = curPage-3;
 var curEnd = curPage+3;
 for(var i=1;i<=pageCount;i++){
 if((i>this.spaceStep && i<curStar)||(i>curEnd && i<pageCount-1)){
  continue;
 }
 if((i==curStar && i>this.spaceStep) || (i==curEnd && i<pageCount-1)){
  steps[i]=this.splitChar;
  continue;
 }
 steps[i]=i;
 }
 return steps;
}

下面是Mytable的实现代码：

function MyTable(tabName,url){
 this.$tab = $("."+tabName);
 this.$wrap = this.$tab.parent();
 this.queryURL = url;
 this.queryData = null;
 this.pager = null;
 this.init();
}
MyTable.prototype.init = function(){
 this.pager = new Pager($("<div class='myPager'><div>").insertAfter(this.$wrap))
  .setPageCallBack($.proxy(this.gotoPage,this));
 this.gotoPage(1);
}

MyTable.prototype.gotoPage = function(curPage){
 if(curPage){
 this.queryData = {"curPage":curPage};
 }
 $.post(this.queryURL,this.queryData,$.proxy(this.show,this),"json");
}

MyTable.prototype.show = function(data){
 this.clear();
 var list = data.list;
 var len = list.length;
 var df = document.createDocumentFragment();
 for(var i=0;i<len;i++){
 var $tr = $("<tr></tr>");
 var $id = $("<td>"+list[i].id+"</td>").appendTo($tr);
 var $name = $("<td>"+list[i].name+"</td>").appendTo($tr);
 var $age = $("<td>"+list[i].age+"</td>").appendTo($tr);
 var $sex = $("<td>"+list[i].sex+"</td>").appendTo($tr);
 df.appendChild($tr[0]);
 }
 this.$tab[0].appendChild(df);
 this.pager.show(data.pager.pageCount, data.pager.curPage, data.pager.rowCount);
}

MyTable.prototype.clear = function(){
 this.$tab.empty();
}

前端页面的处理就是这些，展示效果如下：

第三步：后台的处理

后台的处理很简单，因为是自己写的数据，所以没有做太复杂的处理，首先我先把数据库的数据贴出来

一共18条数据，四个字段，id为主键。下面是controller处理前端请求的代码：

package cn.wangze.controller;

import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import cn.wangze.domain.Employee;
import cn.wangze.domain.Pager;
import cn.wangze.service.BaseService;

@Controller
@RequestMapping("/mam")
public class BaseController extends SuperController{

 @Autowired
 private BaseService<Employee> baseService;

 @RequestMapping(value="/queryListPage")
 public void queryListPage(Employee employee, Pager pager, HttpServletResponse response){
 if(employee == null || pager == null){
  sendError("参数错误",response);
 }
 sendJsonPager(pager, baseService.queryListPage(employee,pager), response);
 }
}

这个页面涉及到了前端返回值得处理，sendError和sendJsonPager方法在它的父类中有声明，代码如下：

public void sendParam(boolean successFlag,Object key,Object value,HttpServletResponse response){
 StringBuffer sb = append(null,SUCCESS,successFlag?SUCCESS:ERROR);
 if(!isEmpty(key)){
  append(sb,key,value);
 }
 if(!MESSAGE.equals(key)){
  append(sb,MESSAGE,successFlag?"操作已成功":"操作以失败");
 }
 writeJsonBuffer(sb.append("}"),response);
}

public void sendMsg(boolean successFlag,String errmsg,HttpServletResponse response){
 sendParam(successFlag,MESSAGE,errmsg,response);
}

public void sendError(String msg,HttpServletResponse response){
 sendMsg(false,msg,response);
}

public void sendJsonPager(Pager pager, List<? extends JsonEntity> list, int i, HttpServletResponse response){
 StringBuffer sb = append(null, MESSAGE, "success");
 if(list==null || list.size()==0){
  sendMsg(false, "查无数据", response);
 }else{
  sb.append(",").append(getJsonList(list,i)).append(pager.toJsonString());
 }
 sb.append("}");
 logger.debug(sb);
 HtmlUtil.writer(response, sb.toString());
 }

 public void sendJsonPager(Pager pager, List<? extends JsonEntity> list, HttpServletResponse response){
 sendJsonPager(pager, list, 0, response);
 }

通过上面BaseController的处理，我们可以看到它调用了BaseService的queryListPager方法，

package cn.wangze.service;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import cn.wangze.domain.Pager;
import cn.wangze.mapper.BaseMapper;

@Service
public class BaseService<T> {

 @Autowired
 private BaseMapper<T> baseMapper;

 public Pager queryRowCount(T t, Pager pager){
 return pager.initRowCount(baseMapper.queryRowCount(t));
 }

 public List<T> queryListPage(T t, Pager pager){
 pager = this.queryRowCount(t,pager);
 if(pager == null) return null;
 return baseMapper.queryListPage(t, pager.getPageSize(), pager.getStart());
 }
}

BaseServie的queryRowCount方法先查询了一下数据的总条数，然后调用了BaseMapper的queryListPage方法，我们来看一下：

package cn.wangze.mapper;

import java.util.List;

import org.apache.ibatis.annotations.Param;

public interface BaseMapper<T> {
 public int queryRowCount(T t);
 public List<T> queryListPage(@Param("t") T t,@Param("end") Integer end,@Param("start") Integer start);
}

这个BaseMapper对应的是mybatis的xml文件，它负责编写sql语句：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.wangze.mapper.BaseMapper">
 <sql id="ColumnList">
 id,name,age,sex
 </sql>
 <sql id="ColumnList_t" >
 t.id,t.name,t.age,t.sex
 </sql>
 <sql id="ValueList">
 #{id},#{name},#{age},#{sex}
 </sql>
 <sql id="WhereClause">
 where 1=1
 <if test="id!=null and id!=''">and id=#{id}</if>
 <if test="name!=null and name!=''">and name=#{name}</if>
 <if test="age!=null and age!=''">and age=#{age}</if>
 <if test="sex!=null and sex!=''">and sex=#{sex}</if>
 </sql>
 <sql id="WhereClause_pager" >
 where 1=1
 <if test="t.id!=null and t.id!=''">and t.id=#{t.id}</if>
 <if test="t.name!=null and t.name!=''">and t.name=#{t.name}</if>
 <if test="t.age!=null">and t.age=#{t.age}</if>
 <if test="t.sex!=null and t.sex!=''">and t.sex=#{t.sex}</if>
 </sql>
 <sql id="SetClause" >
 set
 <trim suffixOverrides="," >
  <if test="id!=null">id=#{id},</if>
  <if test="name!=null">name=#{name},</if>
  <if test="pid!=null">age=#{age},</if>
  <if test="url!=null">sex=#{sex},</if>
 </trim>
 </sql>
 <select id="queryRowCount" resultType="int" parameterType="employee">
 select count(1) from employee <!-- <include refid="WhereClause"/>-->
 </select>
 <select id="queryListPage" resultType="employee">
 <!-- 0-4 3-7 6-10 -->
 select <include refid="ColumnList"/> from employee limit #{start},#{end};
 </select>
</mapper>

最后我们看下employee和pager的实体类把：

package cn.wangze.domain;

public class Employee extends JsonEntity{
 private int id;
 private String name;
 private String age;
 private String sex;
 public int getId() {
 return id;
 }
 public void setId(int id) {
 this.id = id;
 }
 public String getName() {
 return name;
 }
 public void setName(String name) {
 this.name = name;
 }
 public String getAge() {
 return age;
 }
 public void setAge(String age) {
 this.age = age;
 }
 public String getSalary() {
 return sex;
 }
 public void setSalary(String sex) {
 this.sex = sex;
 }
 @Override
 protected void addJsonFields(int i) {
 addField("id", id).addField("name",name).addField("age", age).addField("sex", sex);
 }

 @Override
 public String toString() {
 return "id:"+id+",name:"+name+",age:"+age+",sex:"+sex;
 }
}

package cn.wangze.domain;

public class Pager {
 private int curPage = 1;
 private int pageSize = 5;
 private int start = 0;
 private int end = 0;
 private int pageCount;
 private int rowCount;
 public int getCurPage() {
 return curPage;
 }
 public void setCurPage(int curPage) {
 this.curPage = curPage;
 }
 public int getPageSize() {
 return pageSize;
 }
 public void setPageSize(int pageSize) {
 this.pageSize = pageSize;
 }
 public int getStart() {
 return start;
 }
 public void setStart(int start) {
 this.start = start;
 }
 public int getEnd() {
 return end;
 }
 public void setEnd(int end) {
 this.end = end;
 }
 public int getPageCount() {
 return pageCount;
 }
 public void setPageCount(int pageCount) {
 this.pageCount = pageCount;
 }
 public int getRowCount() {
 return rowCount;
 }
 public void setRowCount(int rowCount) {
 this.rowCount = rowCount;
 }

 public Pager initRowCount(int rowCount) {
 if (rowCount == 0) {
  return null;
 }
 int ps = getPageSize();
 if (ps == 0) {
  ps = 5;
 }
 int pc = (rowCount + ps - 1) / ps;//
 int cp = getCurPage();
 cp = cp > pc ? pc : cp;
 cp = cp < 1 ? 1 : cp;
 this.setPageCount(pc);
 this.setCurPage(cp);
 this.setEnd(cp * ps );
 this.setStart((cp - 1) * ps);
 this.rowCount = rowCount;
 return this;
 }

 public StringBuffer toJsonString() {
 return new StringBuffer(","+"\"pager\":{\"curPage\":\"" + this.curPage
  + "\",\"pageCount\":\"" + this.pageCount + "\",\"rowCount\":\""
  + this.rowCount + "\"}");
 }

 @Override
 public String toString() {
 return "Pager [curPage=" + curPage + ", pageSize=" + pageSize
  + ", start=" + start + ", end=" + end + ", pageCount="
  + pageCount + ", rowCount=" + rowCount + "]";
 }
}

不知道你还记不记得在BaseService的处理方法里面调用了pager的initRowCount方法没，这个方法就是判断当前执行到第几页，从哪个数字开始，到那个数字结束，是分页查询里面一个很关键的方法。

第四步：通过前后端的配合，看下实现后效果：

很low，页面我没做太多处理，这其实是一个table哈哈。

总结

分页查询大概就是这些了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流，谢谢大家对我们的支持。