第7部分

上一篇文章中介紹校驗(yàn)時(shí)提到客戶(hù)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(lèi)，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(lèi)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(lèi)型，長(zhǎng)度為2，主鍵 articleClassName字段：varchar類(lèi)型，長(zhǎng)度為20 articleSubClass表的結(jié)構(gòu)如下： articleClassID字段：char類(lèi)型，長(zhǎng)度為2 articleSubClassID字段：char類(lèi)型，長(zhǎng)度為2與articleClassID一起構(gòu)成主鍵 articleSubClassName字段：varchar類(lèi)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(lèi)

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(lèi)所在行數(shù)private String subJ;//子類(lèi)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(lèi)記數(shù)器int j=0;//小類(lèi)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(lèi)");articleClassForm.setArticleSubClassName("請(qǐng)輸入一個(gè)小類(lèi)");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(lèi)和子類(lèi)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(lèi)別 </title> </head> <body bgcolor="#ffffff"> <h3> 選擇文件所屬類(lèi)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(lèi)*</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(lèi)</html:option><html:optionsCollection name="articleClassForm" property="beanCollection" styleClass="word"/></html:select></td></tr><tr><td align="right">文章小類(lèi)*</td><td><select name="articleSubClassID" Class="word" ><option value="">請(qǐng)選擇一個(gè)小類(lèi)</option></select><SCRIPT language=JavaScript><!--var articleSubClassGroups=document.articleClassForm.articleClassID.options.lengthvar 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.articleSubClassIDfunction articleClassFormredirect(x){for (m=articleSubClassTemp.options.length-1;m>0;m--)articleSubClassTemp.options[m]=nullfor (i=0;i<articleSubClassGroup[x].length;i++){articleSubClassTemp.options[i]=newOption(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(lèi)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。(T111)

本文作者：張永美 羅會(huì)波 湖北省當(dāng)陽(yáng)市國(guó)稅局 可通過(guò)lhbf@sina.com與他們聯(lián)系

轉(zhuǎn)載地址：http://www.cnblogs.com/SGSoft/articles/88251.html

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