JSP and JSTL Tutorials - Tutorial Addendum - JSP Tag Java Interface

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 31 December 18:00   




(Continued from antecedent part...)



The Servlet Chic - TraceTagTest_jsp.java



As we all understand that JSP pages are translated into Servlet classes before


execution. So we infact analysis the construe Servlet chic to see how the


tag addendum ability connects the Servlet chic to the tag class.



To analysis the Servlet chic translated from TraceTagTest.jsp, accessible TraceTagTest_jsp.java


in localjakarta-tomcat-4.1.18workstandalonelocalhost\_, you will see:




package org.apache.jsp;


import javax.servlet.*;


import javax.servlet.http.*;


import javax.servlet.jsp.*;


import org.apache.jasper.runtime.*;


public chic TraceTagTest_jsp extends HttpJspBase {


clandestine changeless java.util.Vector _jspx_includes;


clandestine org.apache.jasper.runtime.TagHandlerPool




accessible TraceTagTest_jsp() {




= new org.apache.jasper.runtime.TagHandlerPool();




accessible java.util.List getIncludes() {


acknowledgment _jspx_includes;




accessible abandoned _jspDestroy() {






accessible abandoned _jspService(HttpServletRequest request,


HttpServletResponse response)


throws java.io.IOException, ServletException {


JspFactory _jspxFactory = null;


javax.servlet.jsp.PageContext pageContext = null;


HttpSession affair = null;


ServletContext appliance = null;


ServletConfig config = null;


JspWriter out = null;


Item page = this;


JspWriter _jspx_out = null;


try {


_jspxFactory = JspFactory.getDefaultFactory();




pageContext = _jspxFactory.getPageContext(this, request, response,


null, true, 8192, true);


appliance = pageContext.getServletContext();


config = pageContext.getServletConfig();


affair = pageContext.getSession();


out = pageContext.getOut();


_jspx_out = out;






if (_jspx_meth_hy_trace_0(pageContext))








} bolt (Throwable t) {


out = _jspx_out;


if (out != absent && out.getBufferSize() != 0)




if (pageContext != null) pageContext.handlePageException(t);


} assuredly {


if (_jspxFactory != null)








clandestine boolean _jspx_meth_hy_trace_0(


javax.servlet.jsp.PageContext pageContext)


throws Throwable {


JspWriter out = pageContext.getOut();


/* ---- hy:trace ---- */


.TraceTag _jspx_th_hy_trace_0 = (.TraceTag)








_jspx_th_hy_trace_0.setMyAtt("my value");


int _jspx_eval_hy_trace_0 = _jspx_th_hy_trace_0.doStartTag();


if (_jspx_eval_hy_trace_0 !=


javax.servlet.jsp.tagext.Tag.SKIP_BODY) {


do {


out.write("JSP body");




int evalDoAfterBody = _jspx_th_hy_trace_0.doAfterBody();


if (evalDoAfterBody !=






} while (true);




if (_jspx_th_hy_trace_0.doEndTag() ==




acknowledgment true;




acknowledgment false;








As you can see, the absolute hy:trace aspect was translated into a adjustment call,


_jspx_meth_hy_trace_0(pageContext). In that method, an item was instantiated


from my trace tag class. Then interface methods were alleged one by one in the


same adjustment as we discussed in the antecedent section. The "do" bend was there


to amend the physique based on the abiding banderole of doAfterBody() call.



After finishing this trace tag example, I had a actual acceptable compassionate of


how the tag interface offered by the addendum ability works now. How about you?



Dummy Accomplishing of IterationTag Interface - TagSupport Class



J2EE supplied a copy implementation, alleged TagSupport, to the IterationTag interface.


If you are architecture a new tag class, you may extend your chic from TagSupport, instead


of apparatus InterationTag. Extending your tag chic from TagSupport gives you


two advantages.



1. Charge to cipher any appropriate method, if you are blessed with the accomplishing of


that adjustment central TagSupport.



2. TagSupport provides you the pageContext item accessible to use. No charge for you


to cipher setPageContext() and save it in your tag object.



Examples of using TagSupport will be cover in my additional addendum on custom tags.





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Article In : Computers & Technology  -  jsp