上一篇文章中介紹校驗(yàn)時(shí)提到客戶邊的校驗(yàn)用到了JavaScript，實(shí)際上用Struts配合JavaScript還可以實(shí)現(xiàn)許多有用的功能，比如，級(jí)聯(lián)下拉菜單的實(shí)現(xiàn)就是一個(gè)典型的例子：

本例假設(shè)要實(shí)現(xiàn)的是一個(gè)文章發(fā)布系統(tǒng)，我們要發(fā)布的文章分為新聞?lì)惡图夹g(shù)類，其中新聞?lì)愑址譃闀r(shí)事新聞和行業(yè)動(dòng)態(tài)；技術(shù)類又分為操作系統(tǒng)、數(shù)據(jù)庫(kù)、和編程語(yǔ)言等，為了便于添加新的條目，所有這些都保存在數(shù)據(jù)庫(kù)表中。

為此，我們建立一個(gè)名為articleClass的表和一個(gè)名為articleSubClass的表。

articleClass表的結(jié)構(gòu)如下：
articleClassID字段：char類型，長(zhǎng)度為2，主鍵
articleClassName字段：varchar類型，長(zhǎng)度為20
articleSubClass表的結(jié)構(gòu)如下：
articleClassID字段：char類型，長(zhǎng)度為2
articleSubClassID字段：char類型，長(zhǎng)度為2與articleClassID一起構(gòu)成主鍵
articleSubClassName字段：varchar類型，長(zhǎng)度為20


表建好后,在articleClass表中錄入如下數(shù)據(jù):如,01、新聞?lì)?#xff1b;02、技術(shù)類

在articleSubClass表中錄入：01、01、時(shí)事新聞；01、02、行業(yè)動(dòng)態(tài)；02、01、操作系統(tǒng)等記錄。到這里，數(shù)據(jù)庫(kù)方面的準(zhǔn)備工作就已做好。

有了前面做登錄例子的基礎(chǔ)，理解下面要進(jìn)行的工作就沒(méi)有什么難點(diǎn)了，我們現(xiàn)在的工作也在原來(lái)mystruts項(xiàng)目中進(jìn)行。首先，建立需要用到的formbean即ArticleClassForm，其代碼如下：

package entity;
import org.apache.struts.action.*;
import javax.servlet.http.*;
import java.util.Collection;

public class ArticleClassForm extends ActionForm {
? //為select的option做準(zhǔn)備
? private Collection beanCollection;
? private String singleSelect = "";
? private String[] beanCollectionSelect = { "" };
? private String articleClassID;
? private String articleClassName;
? private String subI;//子類所在行數(shù)
? private String subJ;//子類所在列數(shù)
? private String articleSubClassID;
? private String articleSubClassName;

? public Collection getBeanCollection(){
??? return beanCollection;
? }

? public void setBeanCollection(Collection beanCollection){
??? this.beanCollection=beanCollection;
? }

? public String getSingleSelect() {
??? return (this.singleSelect);
? }
? public void setSingleSelect(String singleSelect) {
??? this.singleSelect = singleSelect;
? }
? public String[] getBeanCollectionSelect() {
??? return (this.beanCollectionSelect);
? }
? public void setBeanCollectionSelect(String beanCollectionSelect[]) {
??? this.beanCollectionSelect = beanCollectionSelect;
? }

? public String getArticleClassID() {
??? return articleClassID;
? }
? public void setArticleClassID(String articleClassID) {
??? this.articleClassID = articleClassID;
? }
? public String getArticleClassName() {
??? return articleClassName;
? }
? public void setArticleClassName(String articleClassName) {
??? this.articleClassName = articleClassName;
? }

? public String getSubI() {
??? return subI;
? }
? public void setSubI(String subI) {
??? this.subI = subI;
? }

? public String getSubJ() {
??? return subJ;
? }
? public void setSubJ(String subJ) {
??? this.subJ = subJ;
? }

? public String getArticleSubClassID() {
??? return articleSubClassID;
? }
? public void setArticleSubClassID(String articleSubClassID) {
??? this.articleSubClassID = articleSubClassID;
? }

? public String getArticleSubClassName() {
??? return articleSubClassName;
? }
? public void setArticleSubClassName(String articleSubClassName) {
??? this.articleSubClassName = articleSubClassName;
? }
}


將它放在包entity中。其次，我們的系統(tǒng)要訪問(wèn)數(shù)據(jù)庫(kù)，因此也要建立相應(yīng)的數(shù)據(jù)庫(kù)訪問(wèn)對(duì)象ArticleClassDao,其代碼如下：

package db;

import entity.ArticleClassForm;
import db.*;
import java.sql.*;

import java.util.Collection;
import java.util.ArrayList;
import org.apache.struts.util.LabelValueBean;
public class ArticleClassDao {
? private Connection con;

? public ArticleClassDao(Connection con) {
??? this.con=con;
? }
? public Collection findInUseForSelect(){
??? PreparedStatement ps=null;
??? ResultSet rs=null;
??? ArrayList list=new ArrayList();
??? String sql="select * from articleClass order by articleClassID";
??? try{
????? if(con.isClosed()){
??????? throw new IllegalStateException("error.unexpected");
????? }
????? ps=con.prepareStatement(sql);
????? rs=ps.executeQuery();

????? while(rs.next()){
??????? String value=rs.getString("articleClassID");
??????? String label=rs.getString("articleClassName");
??????? list.add(new LabelValueBean(label,value));
????? }
????? return list;
??? }
??? catch(SQLException e){
????? e.printStackTrace();
????? throw new RuntimeException("error.unexpected");
??? }
??? finally{
????? try{
??????? if(ps!=null)
????????? ps.close();
??????? if(rs!=null)
????????? rs.close();

????? }
????? catch(SQLException e){
??????? e.printStackTrace();
??????? throw new RuntimeException("error.unexpected");
????? }
??? }
? }

? public Collection findInUseForSubSelect(){
??? PreparedStatement ps=null;
??? ResultSet rs=null;
??? PreparedStatement psSub=null;
??? ResultSet rsSub=null;
??? int i=0;//大類記數(shù)器
??? int j=0;//小類記數(shù)器
??? String classID="";
??? String subClassID="";
??? String subClassName="";

??? ArrayList list=new ArrayList();
??? ArticleClassForm articleClassForm;


??? String sql="select * from articleClass order by articleClassID";
??? try{
????? if(con.isClosed()){
??????? throw new IllegalStateException("error.unexpected");
????? }
????? ps=con.prepareStatement(sql);
????? rs=ps.executeQuery();

????? while(rs.next()){
??????? i++;
??????? classID=rs.getString("articleClassID");
??????? String sqlSub="select * from articleSubClass where articleClassID=?
??????????? order by articleSubClassID";
??????? psSub=con.prepareStatement(sqlSub);
??????? psSub.setString(1,classID);
??????? rsSub=psSub.executeQuery();

??????? articleClassForm=new ArticleClassForm();
??????? articleClassForm.setSubI(""+i);
??????? articleClassForm.setSubJ(""+j);
??????? articleClassForm.setArticleSubClassID("請(qǐng)輸入一個(gè)小類");
??????? articleClassForm.setArticleSubClassName("請(qǐng)輸入一個(gè)小類");
??????? list.add(articleClassForm);

??????? while(rsSub.next()){
????????? subClassID=rsSub.getString("articleSubClassID");
????????? subClassName=rsSub.getString("articleSubClassName");
????????? j++;
????????? //optionStr="articleSubClassGroup[" + i + "][" + j + "]=
new Option('"+ subClassName +"','"+ subClassID+ "')";
????????? articleClassForm=new ArticleClassForm();
????????? articleClassForm.setSubI(""+i);
????????? articleClassForm.setSubJ(""+j);
????????? articleClassForm.setArticleSubClassID(subClassID);
????????? articleClassForm.setArticleSubClassName(subClassName);
????????? list.add(articleClassForm);
??????? }

??????? j=0;
????? }
????? return list;
??? }
??? catch(SQLException e){
????? e.printStackTrace();
????? throw new RuntimeException("error.unexpected");
??? }
??? finally{
????? try{
??????? if(ps!=null)
????????? ps.close();
??????? if(rs!=null)
????????? rs.close();

????? }
????? catch(SQLException e){
??????? e.printStackTrace();
??????? throw new RuntimeException("error.unexpected");
????? }
??? }
? }
}


將它保存在db目錄中。它們的目的是將文章的類和子類信息從數(shù)據(jù)庫(kù)表中讀出，以一定的格式保存在集合對(duì)象中以供頁(yè)面顯示。

再次,我們要建立相應(yīng)的jsp文件,文件名為selectArticleClass.jsp,代碼如下:

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib uri="/WEB-INF/struts-bean.tld" prefix="bean" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/struts-logic.tld" prefix="logic" %>
<html>
<head>
<title>
選擇文件類別
</title>
</head>
<body bgcolor="#ffffff">
<h3>
選擇文件所屬類型
</h3>
<html:errors/>
<table width="500" border="0" cellspacing="0" cellpadding="0">
? <tr>
??? <td><html:form name="articleClassForm" type="entity.ArticleClassForm"
????? action="selectArticleClassAction.do">
??????? <table width="500" border="0" cellspacing="0" cellpadding="0">
????????? <tr>
??????????? <td align="right">文章大類*</td>
??????????? <td>
????????????? <html:select property="articleClassID" styleClass="word"
?????????????????? οnchange="articleClassFormredirect(this.options.selectedIndex)">
??????????????? <html:option value="">請(qǐng)選擇一個(gè)大類</html:option>
??????????????? <html:optionsCollection name="articleClassForm" property="beanCollection" styleClass="word"/>
????????????? </html:select>
??????????? </td>
????????? </tr>
????????? <tr>
??????????? <td align="right">文章小類*</td>
??????????? <td>
????????????? <select name="articleSubClassID" Class="word" >
??????????????? <option value="">請(qǐng)選擇一個(gè)小類</option>
????????????? </select>
????????????? <SCRIPT language=JavaScript>
????????????? <!--
????????????? var articleSubClassGroups=document.articleClassForm.articleClassID.
?????????????????? options.length
????????????? var articleSubClassGroup=new Array(articleSubClassGroups)
????????????? for (i=0; i<articleSubClassGroups; i++)
????????????? articleSubClassGroup[i]=new Array()
????????????? <logic:iterate name="articleSubClassList" id="articleClassForm"
??????????????????? scope="request" type="entity.ArticleClassForm">
??????????????? articleSubClassGroup[<bean:write name="articleClassForm"
??????????????????????? property="subI"/>][<bean:write name="articleClassForm"
??????????????????????? property="subJ"/>]=new Option("<bean:write name="articleClassForm"
????????????????? property="articleSubClassName"/>","<bean:write name="articleClassForm"
????????????????? property="articleSubClassID"/>")
????????????? </logic:iterate>
????????????? var articleSubClassTemp=document.articleClassForm.articleSubClassID
????????????? function articleClassFormredirect(x){
??????????????? for (m=articleSubClassTemp.options.length-1;m>0;m--)
??????????????? articleSubClassTemp.options[m]=null
??????????????? for (i=0;i<articleSubClassGroup[x].length;i++){
????????????????? articleSubClassTemp.options[i]=new
??????????? Option(articleSubClassGroup[x][i].text,
?????????????????? articleSubClassGroup[x][i].value)
??????????????? }
??????????????? articleSubClassTemp.options[0].selected=true
????????????? }
???????????? //-->
?????????? </SCRIPT>
??????????? </td>
????????? </tr>
??????? </table>
????? </html:form>
??? </td>
? </tr>
</table>
</body>
</html>


這里值得重點(diǎn)關(guān)注的是其中的JavaScript代碼,有興趣的可以仔細(xì)分析一下它們是怎樣配合集合中的元素來(lái)實(shí)現(xiàn)級(jí)聯(lián)選擇的。

最后，為了例子的完整。我們將涉及到action代碼和必要的配置代碼在下面列出：其中，action的文件名為SelectArticleClassAction.java,代碼如下：

package action;
import entity.*;
import org.apache.struts.action.*;
import javax.servlet.http.*;
import javax.sql.DataSource;
import java.sql.Connection;
import db.ArticleClassDao;
import java.util.Collection;
import java.sql.SQLException;
public class SelectArticleClassAction extends Action {
? public ActionForward execute(ActionMapping actionMapping, ActionForm actionForm,
? HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) {
??? /**@todo: complete the business logic here, this is just a skeleton.*/
??? ArticleClassForm articleClassForm = (ArticleClassForm) actionForm;
??? DataSource dataSource;
??? Connection cnn=null;
??? ActionErrors errors=new ActionErrors();
??? try{
????? dataSource = getDataSource(httpServletRequest,"A");
????? cnn = dataSource.getConnection();
????? ArticleClassDao articleClassDao=new ArticleClassDao(cnn);

????? Collection col=articleClassDao.findInUseForSelect();
????? articleClassForm.setBeanCollection(col);
????? httpServletRequest.setAttribute("articleClassList",col);

????? //處理子類選項(xiàng)
????? Collection subCol=articleClassDao.findInUseForSubSelect();
????? httpServletRequest.setAttribute("articleSubClassList",subCol);
????? return actionMapping.findForward("success");
??? }
??? catch(Throwable e){
????? e.printStackTrace();
????? //throw new RuntimeException("未能與數(shù)據(jù)庫(kù)連接");
????? ActionError error=new ActionError(e.getMessage());
????? errors.add(ActionErrors.GLOBAL_ERROR,error);
??? }
??? finally{
????? try{
??????? if(cnn!=null)
????????? cnn.close();
????? }
????? catch(SQLException e){
??????? throw new RuntimeException(e.getMessage());
????? }
??? }
??? saveErrors(httpServletRequest,errors);
??? return actionMapping.findForward("fail");
? }
}


將其保存在action目錄中。

在struts-config.xml文件中做如下配置：

在 <form-beans>
中加入 <form-bean name="articleClassForm" type="entity.ArticleClassForm" />


在 ><action-mappings>
中加入：

<action name="articleClassForm" path="/selectArticleClassAction" scope="session"
????? type="action.SelectArticleClassAction" validate="false">
<forward name="success" path="/selectArticleClass.jsp" />
<forward name="fail" path="/genericError.jsp" />
</action>


為了對(duì)應(yīng)配置中的 <forward name="fail" path="/genericError.jsp" />
,我們還要提供一個(gè)顯示錯(cuò)誤信息的jsp頁(yè)面,其代碼如下:

<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<html>
<head>
<title>
genericError
</title>
<link href="css/mycss.css" rel="stylesheet" type="text/css">
</head>
<body bgcolor="#ffffff">
<html:errors/>
</body>
</html>


現(xiàn)在一切就緒，可以編譯執(zhí)行了。在瀏覽器中輸入：http://127.0.0.1:8080/mystruts/selectArticleClassAction.do就可以看到該例子的運(yùn)行結(jié)果了。(

本文來(lái)自CSDN博客，轉(zhuǎn)載請(qǐng)標(biāo)明出處：file:///H:/雜亂無(wú)章/學(xué)習(xí)資料~~/struts中的javascript%20-%20seinbar的專欄%20-%20CSDN博客.htm

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