Mybatis分页插件PageHelper的学习与使用

目录

• pagehelper使用

后端程序员都知道，在web系统中，分页是一种常见的功能，我之前写的分页方法都比较麻烦，移植性也不高，这就很不乐观了。作为一个积极开朗的程序员，怎么能不去了解pagehelper分页插件呢？pagehelper是国内非常优秀的一款开源的mybatis分页插件，它支持基本主流与常用的数据库，一致支持mysql、oracle、mariadb、db2、sqlite、hsqldb等。ok接下来就一起来了解了解pagehelper分页插件！
@

中文教程

首先，推荐两个pagehelper分页插件项目地址，这里面有中文教程：
github 项目
gitosc 项目

pagehelper使用

至于怎么使用我想上面提供的两个项目讲的绝逼讲的比我清楚，下面直接进入pagehelper使用实战

首先，集成引入分页插件有下面2种方式，一种是直接下jar包一种是mawen依赖，推荐使用 maven 方式。

方法一： 直接下载jar包

，由于使用了sql 解析工具，你还需要下载

方法二： maven添加依赖

  <dependency>
            <groupid>com.github.pagehelper</groupid>
            <artifactid>pagehelper</artifactid>
            <version>5.1.2</version>
  </dependency>

1.导入maven依赖分页插件

我这里就采用方法二maven依赖

2.各个情况下xml的配置

情况一：如果是mybatis单独使用pagehelper分页插件的时候，就需要在xml配置中添加如下代码：

  <!--
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?
  -->
  <!-- com.github.pagehelper为pagehelper类所在包名 -->
    <plugins> 
    <!-- 使用下面的方式配置参数，推荐的两个项目中有所有的参数介绍 -->
        <plugin interceptor="com.github.pagehelper.pageinterceptor"> 
            <property name="param1" value="value1"/>
        </plugin>
    </plugins>

情况二：显然，我是这个是ssm项目，mybatis是交由spring的ioc容器管理的，就需要在spring的xml配置中添加如下代码（创建工厂中添加）：

  <!-- 把交给ioc管理 sqlsessionfactory -->
 <bean id="sqlsessionfactory" class="org.mybatis.spring.sqlsessionfactorybean">
     <property name="datasource" ref="datasource"/>
     <!-- 传入pagehelper的插件 -->
     <property name="plugins">
         <array>
             <!-- 传入插件的对象 -->
             <bean class="com.github.pagehelper.pageinterceptor">
                 <property name="properties">
                     <props>
                         <prop key="helperdialect">oracle</prop>
                         <prop key="reasonable">true</prop>
                     </props>
                 </property>
             </bean>
         </array>
     </property>
 </bean>

下面用一个图来分析一下两个参数作用：

更多情况请参考上面推荐的项目~

3.controller代码编写

上面我们配置完了，至于为什么从controller代码开始是因为controller调用service嘛，这样编写代码更方便快捷！为了看出差别，未分页的controller代码方法如下：

@controller
@requestmapping("/orders")
public class orderscontroller {

    @autowired
    private iordersservice ordersservice;

//查询所有orders未分页
   @requestmapping("/findall.do")
    public modelandview findall() {
        modelandview mv = new modelandview();
        list<orders> orderslist = ordersservice.findall();
        mv.addobject("orderslist", orderslist);
        mv.setviewname("orders-list");
        return mv;
    }
}

而采用了分页代码则是如下：

//采用分页代码方法
   @requestmapping("/findall.do")
    public modelandview findall(@requestparam(name="page",required = true,defaultvalue = "1")int page,@requestparam(name="size",required = true,defaultvalue = "4")int size ) {
        modelandview mv = new modelandview();
        list<orders> orderslist = ordersservice.findall(page,size);

        //pageinfo就是一个分页bean
        pageinfo pageinfo =new pageinfo(orderslist);
        mv.addobject("pageinfo", pageinfo);
        mv.setviewname("orders-list");
        return mv;

    }

可以发现多了两个参数分别是page和size

4.service接口代码编写

public interface iordersservice {
    list<orders> findall(int page,int size);
}

5.service实现类代码编写

在执行sql之前（serviceimpl），使用pagehelper分页，参数pagenum 是页码值 参数pagesize 代表是每页显示条数。在serviceimpl中,使用pagehelper分页操作代码如下：

@service
public class ordersserviceimpl implements iordersservice {
    @autowired
    private iordersdao ordersdao;

    @override
    public list<orders> findall(int page,int size) {
        //参数pagenum 是页码值   参数pagesize 代表是每页显示条数
        pagehelper.startpage(page, size);
        return ordersdao.findall();
    }
}

特别注意：在编写pagehelper分页代码时的 pagehelper.startpage(page, size)这一句必须写在查询方法的上一句，中间不能添加任何代码，否则失效！

6.jsp页面未处理代码

没有更改的jsp页面代码,普通查询关键更改代码块，注意这里接收数据为 orderslist

<c:foreach items="${orderslist}" var="orders">
   <tr>
        <td><input name="ids" type="checkbox"></td>
        ...
        <td>...</td>
        </td>
    </tr>
</c:foreach>

这下面的代码则是未分页逻辑代码

 <div class="box-tools pull-right">
                        <ul class="pagination">
                            <li>
                                <a href="#" aria-label="previous">首页</a>
                            </li>
                            <li><a href="#">上一页</a></li>
                            <li><a href="#">1</a></li>
                            <li><a href="#">2</a></li>
                            <li><a href="#">3</a></li>
                            <li><a href="#">4</a></li>
                            <li><a href="#">5</a></li>
                            <li><a href="#">下一页</a></li>
                            <li>
                                <a href="#" aria-label="next">尾页</a>
                            </li>
                        </ul>
                    </div>

                </div>

7.jsp页面处理后代码

更改后的jsp页面代码,分页查询的关键更改代码块，注意这里接收数据为 orderslist.list

<c:foreach items="${orderslist.list}" var="orders">
   <tr>
        <td><input name="ids" type="checkbox"></td>
        ...
        <td>...</td>
        </td>
    </tr>
</c:foreach>

这下面的代码则是分页逻辑代码

<div class="box-tools pull-right">
   <ul class="pagination">
        <li>
            <a href="${pagecontext.request.contextpath}/orders/findall.do?page=1&size=${pageinfo.pagesize}" aria-label="previous">首页</a>
        </li>
        <li><a href="${pagecontext.request.contextpath}/orders/findall.do?page=${pageinfo.pagenum-1}&size=${pageinfo.pagesize}">上一页</a></li>
        <c:foreach begin="1" end="${pageinfo.pages}" var="pagenum">
            <li><a href="${pagecontext.request.contextpath}/orders/findall.do?page=${pagenum}&size=${pageinfo.pagesize}">${pagenum}</a></li>
        </c:foreach>
        <li><a href="${pagecontext.request.contextpath}/orders/findall.do?page=${pageinfo.pagenum+1}&size=${pageinfo.pagesize}">下一页</a></li>
        <li>
            <a href="${pagecontext.request.contextpath}/orders/findall.do?page=${pageinfo.pages}&size=${pageinfo.pagesize}" aria-label="next">尾页</a>
        </li>
    </ul>
</div>
</div>

8.jsp页面处理前后代码分析

    //pageinfo就是一个分页bean
   pageinfo pageinfo =new pageinfo(orderslist);

为了能看到上面的pageinfo源代码，我就把代码贴在下面了

package com.github.pagehelper;

import java.io.serializable;
import java.util.collection;
import java.util.list;

public class pageinfo<t> implements serializable {
    private static final long serialversionuid = 1l;
    private int pagenum;
    private int pagesize;
    private int size;
    private int startrow;
    private int endrow;
    private long total;
    private int pages;
    private list<t> list;
    private int prepage;
    private int nextpage;
    private boolean isfirstpage;
    private boolean islastpage;
    private boolean haspreviouspage;
    private boolean hasnextpage;
    private int navigatepages;
    private int[] navigatepagenums;
    private int navigatefirstpage;
    private int navigatelastpage;

    public pageinfo() {
        this.isfirstpage = false;
        this.islastpage = false;
        this.haspreviouspage = false;
        this.hasnextpage = false;
    }

    public pageinfo(list<t> list) {
        this(list, 8);
    }

    public pageinfo(list<t> list, int navigatepages) {
        this.isfirstpage = false;
        this.islastpage = false;
        this.haspreviouspage = false;
        this.hasnextpage = false;
        if (list instanceof page) {
            page page = (page)list;
            this.pagenum = page.getpagenum();
            this.pagesize = page.getpagesize();
            this.pages = page.getpages();
            this.list = page;
            this.size = page.size();
            this.total = page.gettotal();
            if (this.size == 0) {
                this.startrow = 0;
                this.endrow = 0;
            } else {
                this.startrow = page.getstartrow() + 1;
                this.endrow = this.startrow - 1 + this.size;
            }
        } else if (list instanceof collection) {
            this.pagenum = 1;
            this.pagesize = list.size();
            this.pages = this.pagesize > 0 ? 1 : 0;
            this.list = list;
            this.size = list.size();
            this.total = (long)list.size();
            this.startrow = 0;
            this.endrow = list.size() > 0 ? list.size() - 1 : 0;
        }

        if (list instanceof collection) {
            this.navigatepages = navigatepages;
            this.calcnavigatepagenums();
            this.calcpage();
            this.judgepageboudary();
        }

    }

    private void calcnavigatepagenums() {
        int i;
        if (this.pages <= this.navigatepages) {
            this.navigatepagenums = new int[this.pages];

            for(i = 0; i < this.pages; ++i) {
                this.navigatepagenums[i] = i + 1;
            }
        } else {
            this.navigatepagenums = new int[this.navigatepages];
            i = this.pagenum - this.navigatepages / 2;
            int endnum = this.pagenum + this.navigatepages / 2;
            int i;
            if (i < 1) {
                i = 1;

                for(i = 0; i < this.navigatepages; ++i) {
                    this.navigatepagenums[i] = i++;
                }
            } else if (endnum > this.pages) {
                endnum = this.pages;

                for(i = this.navigatepages - 1; i >= 0; --i) {
                    this.navigatepagenums[i] = endnum--;
                }
            } else {
                for(i = 0; i < this.navigatepages; ++i) {
                    this.navigatepagenums[i] = i++;
                }
            }
        }

    }

    private void calcpage() {
        if (this.navigatepagenums != null && this.navigatepagenums.length > 0) {
            this.navigatefirstpage = this.navigatepagenums[0];
            this.navigatelastpage = this.navigatepagenums[this.navigatepagenums.length - 1];
            if (this.pagenum > 1) {
                this.prepage = this.pagenum - 1;
            }

            if (this.pagenum < this.pages) {
                this.nextpage = this.pagenum + 1;
            }
        }

    }

    private void judgepageboudary() {
        this.isfirstpage = this.pagenum == 1;
        this.islastpage = this.pagenum == this.pages || this.pages == 0;
        this.haspreviouspage = this.pagenum > 1;
        this.hasnextpage = this.pagenum < this.pages;
    }

    public int getpagenum() {
        return this.pagenum;
    }

    public void setpagenum(int pagenum) {
        this.pagenum = pagenum;
    }

    public int getpagesize() {
        return this.pagesize;
    }

    public void setpagesize(int pagesize) {
        this.pagesize = pagesize;
    }

    public int getsize() {
        return this.size;
    }

    public void setsize(int size) {
        this.size = size;
    }

    public int getstartrow() {
        return this.startrow;
    }

    public void setstartrow(int startrow) {
        this.startrow = startrow;
    }

    public int getendrow() {
        return this.endrow;
    }

    public void setendrow(int endrow) {
        this.endrow = endrow;
    }

    public long gettotal() {
        return this.total;
    }

    public void settotal(long total) {
        this.total = total;
    }

    public int getpages() {
        return this.pages;
    }

    public void setpages(int pages) {
        this.pages = pages;
    }

    public list<t> getlist() {
        return this.list;
    }

    public void setlist(list<t> list) {
        this.list = list;
    }

    /** @deprecated */
    @deprecated
    public int getfirstpage() {
        return this.navigatefirstpage;
    }

    /** @deprecated */
    @deprecated
    public void setfirstpage(int firstpage) {
        this.navigatefirstpage = firstpage;
    }

    public int getprepage() {
        return this.prepage;
    }

    public void setprepage(int prepage) {
        this.prepage = prepage;
    }

    public int getnextpage() {
        return this.nextpage;
    }

    public void setnextpage(int nextpage) {
        this.nextpage = nextpage;
    }

    /** @deprecated */
    @deprecated
    public int getlastpage() {
        return this.navigatelastpage;
    }

    /** @deprecated */
    @deprecated
    public void setlastpage(int lastpage) {
        this.navigatelastpage = lastpage;
    }

    public boolean isisfirstpage() {
        return this.isfirstpage;
    }

    public void setisfirstpage(boolean isfirstpage) {
        this.isfirstpage = isfirstpage;
    }

    public boolean isislastpage() {
        return this.islastpage;
    }

    public void setislastpage(boolean islastpage) {
        this.islastpage = islastpage;
    }

    public boolean ishaspreviouspage() {
        return this.haspreviouspage;
    }

    public void sethaspreviouspage(boolean haspreviouspage) {
        this.haspreviouspage = haspreviouspage;
    }

    public boolean ishasnextpage() {
        return this.hasnextpage;
    }

    public void sethasnextpage(boolean hasnextpage) {
        this.hasnextpage = hasnextpage;
    }

    public int getnavigatepages() {
        return this.navigatepages;
    }

    public void setnavigatepages(int navigatepages) {
        this.navigatepages = navigatepages;
    }

    public int[] getnavigatepagenums() {
        return this.navigatepagenums;
    }

    public void setnavigatepagenums(int[] navigatepagenums) {
        this.navigatepagenums = navigatepagenums;
    }

    public int getnavigatefirstpage() {
        return this.navigatefirstpage;
    }

    public int getnavigatelastpage() {
        return this.navigatelastpage;
    }

    public void setnavigatefirstpage(int navigatefirstpage) {
        this.navigatefirstpage = navigatefirstpage;
    }

    public void setnavigatelastpage(int navigatelastpage) {
        this.navigatelastpage = navigatelastpage;
    }

    public string tostring() {
        stringbuffer sb = new stringbuffer("pageinfo{");
        sb.append("pagenum=").append(this.pagenum);
        sb.append(", pagesize=").append(this.pagesize);
        sb.append(", size=").append(this.size);
        sb.append(", startrow=").append(this.startrow);
        sb.append(", endrow=").append(this.endrow);
        sb.append(", total=").append(this.total);
        sb.append(", pages=").append(this.pages);
        sb.append(", list=").append(this.list);
        sb.append(", prepage=").append(this.prepage);
        sb.append(", nextpage=").append(this.nextpage);
        sb.append(", isfirstpage=").append(this.isfirstpage);
        sb.append(", islastpage=").append(this.islastpage);
        sb.append(", haspreviouspage=").append(this.haspreviouspage);
        sb.append(", hasnextpage=").append(this.hasnextpage);
        sb.append(", navigatepages=").append(this.navigatepages);
        sb.append(", navigatefirstpage=").append(this.navigatefirstpage);
        sb.append(", navigatelastpage=").append(this.navigatelastpage);
        sb.append(", navigatepagenums=");
        if (this.navigatepagenums == null) {
            sb.append("null");
        } else {
            sb.append('[');

            for(int i = 0; i < this.navigatepagenums.length; ++i) {
                sb.append(i == 0 ? "" : ", ").append(this.navigatepagenums[i]);
            }

            sb.append(']');
        }

        sb.append('}');
        return sb.tostring();
    }
}

到这里，基本就ok了，我再次强调我推荐的那两个项目，那里面讲的很详细大佬写的，强调完毕，挥爪~