2018-10-10：分页

分页

  • 真分页
    使用特定的sql语句，条件查询出指定内容

  • 假分页
    数据全部取出，在页面分页显示

  • 分页数据
    pageSize maxResults 每页大小 页面（用户提供或默认值）提供
    itemCount 总记录数 数据库
    offset firstResult 当前页第一条的编号 当前显示第几页(用户) 计算
    pageCount 总页数 计算

总页数 = （总记录数+每页大小 - 1 ）/ 每页大小
当前页第一条的编号 = （当前页编号 - 1） * 每页大小

  • 分页完成步骤

  1. hibernate能分页
    拷贝PageInfo daoimp增加byPage方法 byPage和getAll方法的区别在与要设置max和first，要查询总数

  2. 页面输出能分页
    action调用分页查询的方法，由于分页参数是页面提供，所以pageInfo 设置为action的成员变量，getter setter
    list页面调用分页的方法
    浏览器地址 输入list.jsp?pageInfo.firstResult=15&pageInfo.maxResults=5

  3. 使用自定义分页标签能分页
    拷贝分页标签类 和 分页标签的tld文件 tld文件放在web-inf 检查tld文件中类的路径名称是否匹配
    list页面 添加自定义标签的引入
    <%@ taglib prefix="paging" uri="/WEB-INF/paging.tld" %>

记得设置base标签

<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<s:action name="courseAction_getAllCourse" executeResult="false"
namespace="/" />
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>" />

拷贝标签的调用

<tr>
<td colspan="8">
<paging:paging
href="student/list.jsp"
itemCount="{pageInfo.itemCount}" firstResult="{pageInfo.firstResult}"
maxResults="${pageInfo.maxResults}"/>
</td></tr>

PageInfo.java:

package repairsystem.page;


import java.io.Serializable;


public class PageInfo implements Serializable {

    private static final long serialVersionUID = 1878154374135400744L;

    private int firstResult = 0;//当前页第一条编号 

    private int maxResults = 5;//每页大小

    private int pageCount = 0;//总页数

    private transient int itemCount = 0;//总记录数
    
    public boolean isPage = false;



    public int getFirstResult() {
        return firstResult;
    }



    public void setFirstResult(int firstResult) {
        this.firstResult = firstResult;
    }



    public int getMaxResults() {
        return maxResults;
    }



    public void setMaxResults(int maxResults) {
        this.maxResults = maxResults;
    }



    public int getPageCount() {
        return pageCount;
    }



    public void setPageCount(int pageCount) {
        this.pageCount = pageCount;
    }



    public boolean isPage() {
        return isPage;
    }



    public void setPage(boolean isPage) {
        this.isPage = isPage;
    }



    public int getItemCount() {
        return itemCount;
    }



    public void setItemCount(int itemCount) {
        this.itemCount = itemCount;
        this.pageCount = (itemCount + maxResults - 1) / maxResults;
    }

    

 
}

PagingTag.java:

package repairsystem.page;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;


/**
 * @author vikings
 *
 */
public class PagingTag extends TagSupport{

    private static final long serialVersionUID = 1L;

    private int maxResults = 5; 
    private int firstResult=0; 
    private int itemCount = 0;
    private String href = null;
        


    
    public int getMaxResults() {
        return maxResults;
    }

    public void setMaxResults(int maxResults) {
        this.maxResults = maxResults;
    }

    public int getFirstResult() {
        return firstResult;
    }

    public void setFirstResult(int firstResult) {
        this.firstResult = firstResult;
    }

    public int getItemCount() {
        return itemCount;
    }

    public void setItemCount(int itemCount) {
        this.itemCount = itemCount;
    }

    public String getHref() {
        return href;
    }

    public void setHref(String href) {
        this.href = href;
    }

    public int doStartTag() throws JspException 
    {
      return SKIP_BODY;
    }
    
    public int doEndTag() throws JspException 
    {   

        
        int totalPages = 0;
        int currentPage=0;

        totalPages = itemCount / maxResults;
        if(itemCount==0||maxResults==0){
          return EVAL_PAGE;
        }
        if (itemCount % maxResults != 0) {
          totalPages = totalPages + 1;
        }
        if (totalPages<=1)
        {
          return EVAL_PAGE;
        }
        currentPage = (firstResult) / maxResults;
        currentPage = currentPage+1;
        StringBuffer navigation = new StringBuffer();
        navigation.append("<li><a>第"+currentPage+"页/共"+totalPages+"页</a></li>");
        if (currentPage<=1){
          navigation.append("<li><a>首页</a></li>");
          navigation.append("<li><a>上一页</a></li>");
        } else {
          navigation.append("<li><a href='"+href+"?pageInfo.firstResult=0&pageInfo.maxResults="+maxResults+"&pageInfo.isPage=true'>首页</a></li>");
          navigation.append("&nbsp;");
          navigation.append("<li><a href='"+href+"?pageInfo.firstResult="+(firstResult-maxResults)+"&pageInfo.maxResults="+maxResults+"&pageInfo.isPage=true'>上一页</a></li>");
        }
        navigation.append("&nbsp;");
        if (currentPage>=totalPages){
          navigation.append("<li><a>下一页</a></li>");
          navigation.append("&nbsp;");
          navigation.append("<li><a>尾页</a></li>");
        }else {
          navigation.append("<li><a href='"+href+"?pageInfo.firstResult="+(firstResult+maxResults)+"&pageInfo.maxResults="+maxResults+"&pageInfo.isPage=true'>下一页</a></li>");
          navigation.append("&nbsp;");
          navigation.append("<li><a href='"+href+"?pageInfo.firstResult="+((totalPages-1)*maxResults)+"&pageInfo.maxResults="+maxResults+"&pageInfo.isPage=true'>尾页&nbsp;</a></li>");
        }
        try {
            pageContext.getOut().print(navigation.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
       
      return EVAL_PAGE;
    }
    
    public void release() 
    {       
        super.release();
        this.maxResults = 0; //recordsPerPage
        this.firstResult=0; //beginItem
        this.itemCount = 0;
        this.href = null;
    }
}

paging.tld:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
                        "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
 <tlibversion>1.0</tlibversion>
 <jspversion>1.1</jspversion>
 <shortname>Jsp Tag Library</shortname>
   <!--  paging标签，用于显示一个分页的公告表格 -->
 <tag>
  <name>paging</name>
  <tagclass>repairsystem.page.PagingTag</tagclass>
  <bodycontent>empty</bodycontent>
  <attribute>
   <name>maxResults</name>
   <rtexprvalue>true</rtexprvalue>
  </attribute>
  <attribute>
   <name>firstResult</name>
   <rtexprvalue>true</rtexprvalue>
  </attribute>
  <attribute>
   <name>itemCount</name>
   <required>true</required>
   <rtexprvalue>true</rtexprvalue>
  </attribute>
  <attribute>
   <name>href</name>
   <required>true</required>
   <rtexprvalue>true</rtexprvalue>
  </attribute>
 </tag>
</taglib>

ServicemanDao.java:

    // 分页查询
    public List<Serviceman> getServicemanByPage(PageInfo pageInfo) {
        Query query = session.createQuery("From Serviceman");
        List<Serviceman> servicemans = null;
        int itemCount = getItemCount();// 查询总记录数
        pageInfo.setItemCount(itemCount);
        // 总记录数大于0，才进行分页
        if (itemCount > 0) {

            query.setMaxResults(pageInfo.getMaxResults());
            query.setFirstResult(pageInfo.getFirstResult());
            servicemans = query.list();

        }
        // HibernateSessionFactory.closeSession();
        return servicemans;

    }
    // 查询总记录数

    public int getItemCount() {
        Query query = session.createQuery("select count(*) From Serviceman");
        int itemCount = Integer.parseInt(query.uniqueResult().toString());
        // HibernateSessionFactory.closeSession();
        return itemCount;

    }

...
ServicemanAction.java:

public class ServicemanAction extends ActionSupport{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Serviceman serviceman;
    private ServicemanServiceI servicemanServiceI;
    private PageInfo pageInfo;
    
    public ServicemanAction() {
        super();
        servicemanServiceI = new ServicemanService();
        pageInfo = new PageInfo();
    }
    public Serviceman getServiceman() {
        return serviceman;
    }
    public void setServiceman(Serviceman serviceman) {
        this.serviceman = serviceman;
    }
    public ServicemanServiceI getServicemanServiceI() {
        return servicemanServiceI;
    }
    public void setServicemanServiceI(ServicemanServiceI servicemanServiceI) {
        this.servicemanServiceI = servicemanServiceI;
    }
    
    
    public PageInfo getPageInfo() {
        return pageInfo;
    }
    public void setPageInfo(PageInfo pageInfo) {
        this.pageInfo = pageInfo;
    }
    // 得到所有维修人员信息
    public String getServicemanInfo() throws Exception {
        List<Serviceman> servicemans = servicemanServiceI.getServicemanInfo();
        ServletActionContext.getRequest().setAttribute("servicemans", servicemans);
        return null;
    }
    
    // 分页显示教师
    public String getServicemanByPage() throws Exception {
        // action依次调用service dao后得到结果，再原路返回结果到了action，再将结果转发给页面
        System.out.println(pageInfo.getFirstResult() + "  " + pageInfo.getMaxResults());
        List<Serviceman> servicemans = servicemanServiceI.getServicemanByPage(pageInfo);
        ServletActionContext.getRequest().setAttribute("servicemans", servicemans);
        ServletActionContext.getRequest().setAttribute("pageInfo", pageInfo);
        return null;
    }

    // 根据主键查询维修人员
    public String getServicemanInfoBySid() throws Exception {
        Serviceman dbserviceman = servicemanServiceI.getServicemanInfoBySid(serviceman.getSid());
        ServletActionContext.getRequest().setAttribute("serviceman", dbserviceman);
        // System.out.println(dbteacher.getTname());
        return null;
    }

    // 增加维修人员
    public String addServiceman() throws Exception {
        Serializable result = servicemanServiceI.addServiceman(serviceman);
        return null;
    }

    // 修改维修人员信息
    public String updateServiceman() throws Exception {
        Serializable result = servicemanServiceI.updateServiceman(serviceman);
        return null;
    }
}

serviceman.jsp:

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<%@ taglib prefix="paging" uri="/WEB-INF/paging.tld" %>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
            + path + "/";

%>
<s:action name="ServicemanAction_getServicemanInfo" executeResult="false"
                namespace="/" />
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<base href="<%=basePath%>" />
<title>test</title>
</head>
<body>
    <s:action name="ServicemanAction_getServicemanByPage" executeResult="false" namespace="/"/>
    <table border="1">
        <tr>
            <td>维修者id</td>
            <td>姓名</td>
            <td>电话</td>
            <td>密码</td>
            <td>住址</td>
            <td>状态</td>
            <td colspan="4">操作</td>
        </tr>
        <s:iterator var="serviceman" value="#request.servicemans">
            <tr>
                <td><s:property value="#serviceman.sid" /></td>
                <td><s:property value="#serviceman.sname" /></td>
                <td><s:property value="#serviceman.sphone" /></td>
                <td><s:property value="#serviceman.spassword" /></td>
                <td><s:property value="#serviceman.saddress" /></td>
                <td><s:property value="#serviceman.sstatus" /></td>
                <td><a href="detail.jsp?sid=${serviceman.sid}">详情</a></td>
                <td><a href="update.jsp?sid=${serviceman.sid}">修改</a></td>
                <td>删除</td>
                <td><a href="rob.jsp?sid=${serviceman.sid}">抢单</a></td> 
            </tr>
        </s:iterator>
        <tr>
            <td><a href="add.jsp">增加</a></td>
        </tr>
        <tr>
         <td colspan="8">
           <paging:paging 
           href="Serviceman/serviceman.jsp" 
           itemCount="${pageInfo.itemCount}" 
           firstResult="${pageInfo.firstResult}" 
           maxResults="${pageInfo.maxResults}"/>
         </td>
        </tr>
    </table>
</body>
</html>
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