Home > Developer > Web Develop
Recently new company, browse the new company project, found that most of the JSP pages in the project are separate, complete pages, so many pages will have the following duplicate code:
<%@ Page Language="Java"ContentType="text/html; Charset=utf-8"Import="Java.util.Calendar"Pageencoding="UTF-8"%><%@ taglib Prefix="C"Uri="Http://java.sun.com/jsp/jstl/core"%><%@ taglib Prefix="Fn"Uri="Http://java.sun.com/jsp/jstl/functions"%><%@ taglib URI="Http://java.sun.com/jsp/jstl/fmt"Prefix="Fmt"%><%@ taglib URI="/common-tags"Prefix="M"%><C:setVar= "CTX"Value= "${pagecontext.request.contextpath}"></C:set><!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd "><Htmlxmlns= "Http://www.w3.org/1999/xhtml"><Head><MetaHttp-equiv= "Content-type"Content= "text/html; Charset=utf-8 "/><Title>${webmodule.module.name}---xxxx</Title><MetaName= "keywords"Content= "XXXX"/><MetaName= "description"Content= "XXXX"/><LinkRel= "stylesheet"Href= "${ctx}/css/web-bbs.css"/><LinkRel= "stylesheet"Href= "${ctx}/css/page.css"/><ScriptType= "Text/javascript"Src= "${ctx}/js/jquery-1.7.2.min.js"></Script><ScriptType= "Text/javascript"Src= "${ctx}/js/bbs.js"></Script><ScriptType= "Text/javascript"Src= "${ctx}/js/webutil.js"></script>< Span style= "color: #0000ff;" ><script type= " Text/javascript " Src=" ${ctx}/js/index.js "></script> <script type= "text /javascript " Src=" ${ctx}/js/faces.js "></script>
Small partners Each new page, you need to copy a copy of the above code, but also in their respective pages to introduce the common Kinsoku files (such as header.jsp,footer.jsp) ...
For this kind of development, the duplication of work is not much described, the more important problem is that the future of this architecture will lead to more maintenance work, or even a bug.
Two "chestnuts":
The above pull so much, in fact, the core problem is that all JSP pages are fighting each other, there is no unified public template to maintain some of the global information, so here is the introduction of our previous implementation scenario:
With the template will be able to write this page:
The benefits of this writing are obvious:
The template content is probably like this:
Implementation principleThe implementation of the principle is very simple, the implementation of the template function is mainly two custom tags (custom label development steps are not spoken here)
BlocktagThis label is primarily used to define the appropriate module in the template file (which can be considered a placeholder), and the location of the label definition is replaced with the content of the page rewrite when the JSP page is rendered. The replacement reads content from the attribute of the request based on the label's Name property plus a specific prefix as the key value.
/*** Custom tags for placeholders in JSP templates * *@authorThe feather of the wind **/PublicClass BlocktagExtendsBodytagsupport {/*** Placeholder Module name*/PrivateString name;PrivateStaticFinalLong Serialversionuid = 1425068108614007667L; @OverridePublicint doStartTag ()Throwsjspexception{ReturnSuper. doStartTag (); } @OverridePublicint Doendtag ()Throwsjspexception {ServletRequest request =Pagecontext.getrequest ();//Default value in the block tag String defaultcontent = (getbodycontent () = =NULL)? "": Getbodycontent (). getString (); String bodycontent = (string) request.getattribute (overwritetag.prefix+name);//If the page does not override the module, the default content bodycontent = Stringutils.isempty (bodycontent) is displayed.Defaultcontent:bodycontent;Try{pagecontext.getout (). write (bodycontent);}Catch (IOException e) { // TODO auto-generated catch block e.printstacktrace ();} // TODO auto-generated method stub return Super. Doendtag ();} public String getName () { return name;} Public void setName (String name) { this.name = name;}} Blocktag CodeOverwritetag
This label is primarily used to rewrite the corresponding module in the template on the final page, and the contents of the label are written to the attribute of the current request when the page is rendered, and the label has a required parameter Name property as the key value for the content. This name property must be the same as the name value of the block in the template that corresponds to the override.
/*** Custom tags for overriding specified placeholder content in a JSP template * * Rationale: * Add the Overwrite label content section to the attribute attribute of ServletRequest * in subsequent block tags through the property name Read it and render it to the final page * *@authorThe feather of the wind **/PublicClass OverwritetagExtendsBodytagsupport {PrivateStaticFinalLong Serialversionuid = 5901780136314677968L;//Prefix of module namePublicStaticFinal String PREFIX = "Jsptemplateblockname_";//Module namePrivateString name; @OverridePublicint doStartTag ()Throwsjspexception {//TODO auto-generated Method StubReturnSuper. doStartTag (); } @OverridePublicint Doendtag ()Throwsjspexception {ServletRequest request =Pagecontext.getrequest ();// tag content bodycontent bodycontent = Getbodycontent (); Request.setattribute (Prefix+name, Stringutils.trim (bodycontent.getstring ())); Span style= "color: #008000;" >// TODO auto-generated method stub return super.doendtag ();} public String GetName () { return name; public void SetName ( String name {this.name = name;}} Overwritetag CodeSummary and Development
JSP Template inheritance function implementation
Start building with 50+ products and up to 12 months usage for Elastic Compute Service
1 on 1 presale consultation
24/7 Technical Support 6 Free Tickets per Quarter Faster Response
Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.
A comprehensive suite of global cloud computing services to power your business
Payment Methods We Support
