解决Struts分页显示

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博客围绕Struts、SQL Server数据库展开，涉及action、bean等相关内容，可能包含在数据库操作中运用Struts框架的相关信息技术知识。

解决Struts分页显示

2004年9月11日作者：李敏强 Matrix-与Java共舞

解决Struts分页显示
作者：李敏强  eMail: mill_lmq@tom.com

学习Struts已经有2个多月了，前几天群里的朋友问我Struts分页显示的问题，觉得好像与在jsp中的差不多，但还是遇到了这样那样的问题，好不容易花了几天时间把问题都搞清楚，觉得还是写点东西跟大家分享一下的好！
至于Struts的语法这里就不多介绍了，不懂的朋友可以先看网上的其他文章。

一开发环境
Elicpse+Struts Studio+SqlServer2000+Tomcat。

二开发思路
既然讲的是Struts，那自然离不了MVC，分页显示也是如此。

1 建立适当的模型组件，对应你要查询数据库中的表。这部分由我们熟悉的javaBean来充当。并在其中建立数据库查询方法，该方法需要一个java.sql.Conntection类型的参数，并返回一个ArrayList。在本例中为 Book.java

2 建立分页所需要的模型组件，也是由javaBean来充当，通过由Book中提供的ArrayList来构造。本例中为 PageBean.java.。

3建立控制器组件，这部分由Struts 中的Action来实现。主要负责将实例化Book，并利用返回的ArrayList对象，构造PageBean。以及接收由视图传递而来的action参数。从而在PageBean对象中调用不同的方法，该方法返回Book[] 对象。最后将 Book[]和PageBean放入request中。本例中为PageListAction.java。

4建立视图组件，这部分由jsp来充当，为了不出现java 代码，我们使用Struts提供的标签库，主要负责从request中取出刚刚放入的对象，通过反复调用PageListAction以及action参数，而实现分页显示。本例中为pagetest.jsp.
5 建立并配置struts-config.xml。
6 建立数据库。

三实例代码
1 Book.java

package bean;
import java.sql.*;
import java.util.ArrayList;
/**
* @作者李敏强
* Struts分页显示数据Bean，对应数据库中Book表
*/
public class Book {
private String bookname; //书名
private String author;   //作者
private String price;    //价格

public Book(String name,String author,String price){
this.bookname=name;
this.author=author;
this.price=price;
}

public String getAuthor() {
  return author;
}

public void setAuthor(String author) {
  this.author = author;
}

public String getBookname() {
  return bookname;
}

public void setBookname(String bookname) {
  this.bookname = bookname;
}

public String getPrice(){
     return this.price;
}

public void setPrice(String price){
     this.price=price;
}

public static ArrayList getAllBook(Connection connection){
   String sql="select * from book";
   ArrayList arrayList = new ArrayList();
   try{
   Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
   ResultSet resultSet = statement.executeQuery(sql);
         System.out.println("BookBean 数据查询已完成！");
      while(resultSet.next())
      {
        String name = resultSet.getString("name");
        String author = resultSet.getString("author");
        String price = resultSet.getString("price");
        System.out.println("开始数据封装：name="+name+"author="+author+"price="+price);
        Book book = new Book(name,author,price);
        arrayList.add(book);
      }
    connection.close();
    resultSet.close();
   }catch(SQLException e)
   {
    System.out.println("数据库异常"+e.toString());
   }

      return arrayList;
}
}

2 PageBean.java
package page;
import bean.Book;
import java.util.*;
/**
* @作者李敏强
* Struts分页显示逻辑Bean
*/
public class PageBean {

int currentPage=1;  //当前页
public int totalPages=0;  //总页数
int pageRecorders=5;//每页5条数据
int totalRows=0;  //总数据数
int pageStartRow=0;//每页的起始数
int pageEndRow=0;  //每页显示数据的终止数
boolean hasNextPage=false; //是否有下一页
boolean hasPreviousPage=false; //是否有前一页
ArrayList arrayList;
Iterator it;
public PageBean(){}

public PageBean(ArrayList arrayList){
this.arrayList=arrayList;
totalRows=arrayList.size();
    it=arrayList.iterator();
hasPreviousPage=false;
currentPage=1;
if((totalRows%pageRecorders)==0)
{
totalPages=totalRows/pageRecorders;
}
else
{
  totalPages=totalRows/pageRecorders+1;
}

if(currentPage>=totalPages)
{
  hasNextPage=false;
}
else
{
  hasNextPage=true;
}


    if(totalRows<pageRecorders)
    {
    this.pageStartRow=0;
    this.pageEndRow=totalRows;
    }
    else
    {
    this.pageStartRow=0;
    this.pageEndRow=pageRecorders;
    }

}

/**
  * @return Returns the currentPage.
  */
public String getCurrentPage() {
  return this.toString(currentPage);
}
/**
  * @param currentPage The currentPage to set.
  */
public void setCurrentPage(int currentPage) {
  this.currentPage = currentPage;
}
/**
  * @return Returns the pageRecorders.
  */
public int getPageRecorders() {
  return pageRecorders;
}
/**
  * @param pageRecorders The pageRecorders to set.
  */
public void setPageRecorders(int pageRecorders) {
  this.pageRecorders = pageRecorders;
}
/**
  * @return Returns the pageEndRow.
  */
public int getPageEndRow() {
  return pageEndRow;
}
/**
  * @return Returns the pageStartRow.
  */
public int getPageStartRow() {
  return pageStartRow;
}
/**
  * @return Returns the totalPages.
  */
public String getTotalPages() {

  return this.toString(totalPages);
}
/**
  * @return Returns the totalRows.
  */
public String getTotalRows() {
  return this.toString(totalRows);
}
/**
  * @return Returns the hasNextPage.
  */
public boolean isHasNextPage() {
  return hasNextPage;
}
/**
  * @param hasNextPage The hasNextPage to set.
  */
public void setHasNextPage(boolean hasNextPage) {
  this.hasNextPage = hasNextPage;
}
/**
  * @return Returns the hasPreviousPage.
  */
public boolean isHasPreviousPage() {
  return hasPreviousPage;
}
/**
  * @param hasPreviousPage The hasPreviousPage to set.
  */
public void setHasPreviousPage(boolean hasPreviousPage) {
  this.hasPreviousPage = hasPreviousPage;
}
public Book[] getNextPage(){

currentPage=currentPage+1;
System.out.println("PageBean.getNextPage()正在执行；");
System.out.println("参数currentPage="+currentPage);

if((currentPage-1)>0)
{
  hasPreviousPage=true;
}
    else
    {
     hasPreviousPage=false;
    }

if(currentPage>=totalPages)
{
  hasNextPage=false;
}
else
{
  hasNextPage=true;
}
System.out.println("参数hasNextPage="+hasNextPage);
System.out.println("准备执行PageBean.getBooks()");
Book[] books=getBooks();
this.description();

return books;
}

public Book[] getPreviouspage(){

currentPage=currentPage-1;

    if(currentPage==0){currentPage=1;}

if(currentPage>=totalPages)
{
  hasNextPage=false;
}
else
{
  hasNextPage=true;
}
if((currentPage-1)>0)
{
  hasPreviousPage=true;
}
    else
    {
     hasPreviousPage=false;
    }
Book[] books=getBooks();
this.description();
return books;
}

public Book[] getBooks(){
System.out.println("pageBean.getBooks（）开始执行；");

if(currentPage*pageRecorders<totalRows){//判断是否为最后一页
  pageEndRow=currentPage*pageRecorders;
     pageStartRow=pageEndRow-pageRecorders;
}
else{
  pageEndRow=totalRows;
  pageStartRow=pageRecorders*(totalPages-1);
}
Book[] books=new Book[pageEndRow-pageStartRow+1];

System.out.println("pageStartRow="+pageStartRow);
System.out.println("pageEndRow="+pageEndRow);
  int j=0;
for(int i=pageStartRow;i<pageEndRow;i++)
{

  Book book=(Book)arrayList.get(i);
  books[j++]=book;

}
System.out.println("要显示的页面数据已经封装,具体信息如下：");
this.description();
return books;
}

public String toString(int temp)
{
String str=Integer.toString(temp);
return str;
}

public void description()
{

   String description="共有数据数:"+this.getTotalRows()+

   "共有页数: "+this.getTotalPages() +

   "当前页数为:"+this.getCurrentPage()+

   " 是否有前一页: "+this.isHasPreviousPage() +

   " 是否有下一页:"+this.isHasNextPage()+

   " 开始行数:"+this.getPageStartRow()+

   " 终止行数:"+this.getPageEndRow();

   System.out.println(description);

}
}

3  PageListAction.java
package page;
import org.apache.struts.action.*;
import javax.servlet.http.*;
import comm.Constants;

import bean.Book;
import java.util.*;
import javax.sql.DataSource;
/**
* @author 李敏强
* Struts分页显示Action
*/
public class PageListAction extends Action {

public PageListAction(){}
ArrayList arrayList=new ArrayList();
    PageBean pb;

public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception {
String action;
action=request.getParameter("action");
if(action==null || action.equals("null")){ //第一次读取数据
try{
DataSource datasource=this.getDataSource(request,Constants.DATASOURCE_KEY);
arrayList=Book.getAllBook(datasource.getConnection());
System.out.println("第一步，数据已经成功传递到Action，action="+action);
   }catch(Exception e){
          e.printStackTrace();
  System.out.println("数据库连接出现异常");
      }

     pb=new PageBean(arrayList);
          Book[] books=pb.getBooks();
          pb.description();
          request.setAttribute("result",books);
          request.setAttribute("page",pb);

   }
   else
   {
  if(action=="nextPage" || action.equals("nextPage"))
  {
  System.out.println("参数action="+action);
  System.out.println("函数pb.getNextPage()准备执行");
  Book[]books=pb.getNextPage();
  request.setAttribute("page",pb);
request.setAttribute("result",books);
    }
if(action=="previousPage" || action.equals("previousPage"))
  {
  System.out.println("参数action="+action);
  System.out.println("函数pb.getPreviouspage()准备执行");
  Book[] books=pb.getPreviouspage();
  request.setAttribute("page",pb);
               request.setAttribute("result",books);

    }
   }
   return (mapping.findForward("success"));
  }
}

4 pagetest.jsp
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ page contentType="text/html; charset=gb2312" language="java"%>

<html:html locale="true">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body>

<table border="1">
<tr><th>书名</th><th>作者</th><th>价格</th></tr>
<logic:present name="result">
<logic:iterate id="book" name="result"  type="bean.Book" >
<logic:present name="book">
<tr>
<td><bean:write name="book" property="bookname" /></td>
<td> <bean:write name="book" property="author" /></td>
<td><bean:write name="book" property="price" /></td>
</tr>
</logic:present>
</logic:iterate>
</logic:present>
</table>
<logic:equal name="page" property="hasNextPage" value="true">
<html:link page="/page.do?action=nextPage">nextPage</html:link>
</logic:equal>
<logic:equal name="page" property="hasPreviousPage" value="true">
<html:link page="/page.do?action=previousPage">PreviousPage</html:link>
</logic:equal>
共有数据总数<bean:write name="page" property="totalRows"/>;
共分<bean:write name="page" property="totalPages"/>页,当前是第
<bean:write name="page" property="currentPage"/>页
</body>
</html:html>

5 struts-config.xml
<?xml version="1.0" encoding="ISO-8859-1" ?>

<!DOCTYPE struts-config PUBLIC
          "-//Apache Software Foundation//DTD Struts Configuration 1.1//EN"
          "

http://jakarta.apache.org/struts/dtds/struts-config_1_1.dtd";>

<struts-config>
<data-sources>
  <data-source key="dataSource" type="org.apache.commons.dbcp.BasicDataSource">
   <set-property property="driverClassName" value="com.microsoft.jdbc.sqlserver.SQLServerDriver"/>
   <set-property property="url" value="jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=eBookStore;SelectMethod=cursor"/>
   <set-property property="username" value="limq"/>
   <set-property property="password" value="1"/>
   <set-property property="maxActive" value="10"/>
   <set-property property="maxWait" value="5000"/>
   <set-property property="defaultAutoCommit" value="true"/>
   <set-property property="defaultReadOnly" value="false"/>
  </data-source>
</data-sources>
  <form-beans>
  </form-beans>
  <global-forwards>
  </global-forwards>
  <action-mappings>
  <action path="/page" type="page.PageListAction" scope="request">
  <forward name="success" path="/pagetest.jsp"/>
  </action>
  </action-mappings>
  <controller>
  </controller>
</struts-config>

6 建立eBookStore数据库，以及表book（name,author,parce）;其中数据的配置可以根据你的不同情况在struts-config.xml中而定。

7 Constants.java

package comm;

/**
* this interface provides the constant string for applicator constant
*/
public class Constants {
  /**
    * name of the User Object in HttpSession
    */
   public static String USER_KEY="user";
   /**
    * dataSource name
    */
   public static String DATASOURCE_KEY="dataSource";
}