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Struts原理与实践（7）
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在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、和編程語言等，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，長度為2，主鍵
articleClassName字段：varchar類型，長度為20
articleSubClass表的結(jié)構(gòu)如下：
articleClassID字段：char類型，長度為2
articleSubClassID字段：char類型，長度為2與articleClassID一起構(gòu)成主鍵
articleSubClassName字段：varchar類型，長度為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)行的工作就沒有什么難點(diǎn)了，我們現(xiàn)在的工作也在原來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?{ ?? ???? ??private?Collection?beanCollection; ?? ??private?String?singleSelect?=?""; ?? ??private?String[]?beanCollectionSelect?=?{?""?}; ?? ??private?String?articleClassID; ?? ??private?String?articleClassName; ?? ??private?String?subI;?? ??private?String?subJ;?? ??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)要訪問數(shù)據(jù)庫，因此也要建立相應(yīng)的數(shù)據(jù)庫訪問對(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;?? ????int?j=0;?? ????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++; ?? ???????????? 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)庫表中讀出，以一定的格式保存在集合對(duì)象中以供頁面顯示。
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"?? ?????????????onchange="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)?{ ?? ?????? ????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); ?? ?? ???????? ??????Collection?subCol=articleClassDao.findInUseForSubSelect(); ?? ??????httpServletRequest.setAttribute("articleSubClassList",subCol); ?? ??????return?actionMapping.findForward("success"); ?? ????} ?? ????catch(Throwable?e){ ?? ??????e.printStackTrace(); ?? ???????? ??????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頁面,代碼加入:?
<html:errors?/>??
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)
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