Jsp tag file例子以及说明

简介
Jsp2.0后，实现tag的方式除了taglib(TLD)的方式外，还可以通过定义tag文件来代替taglib类。tag file一般放在/WEB-INF/tags目录或者其子目录,需要在jsp文件中指定uri。

例子1 将tag file作为内容直接引入
firstTagTest.jsp

[java]
<%@ page contentType="text/html; charset=UTF-8" %>
<%@ taglib prefix="easy" tagdir="/WEB-INF/tags" %>
Today is <easy:firstTag/> //包含tag，没有参数传递

firstTag.tag

[java]
//直接被firstTagTest.jsp引入编译为java/class文件
<%@ tag import="java.util.Date" import="java.text.DateFormat"%>
<% 一时手易做图，把structs-config.xml文件中的一段话删了，结果老是报错。
报错内容：Document is invalid: no grammar found
[html] view plaincopyprint?
<?xml version="1.0" encoding="UTF-8"?>
<strong><span style="color:#ff0000;"><!DOCTYPE struts-config PUBLIC
       "-//Apache Software Foundation//DTD Tiles Configuration 1.3//EN"
       "http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd"></span></strong>
<struts-config>
    <form-beans>
        <form-bean name="helloForm" type="com.mars.demo01.structs01.form.HelloForm" />
    </form-beans>
    
    <global-exceptions />
    <global-forwards />
    <action-mappings>
        <action attribute="helloForm" input="/demo01/demo01_hello.jsp"
            name="helloForm" path="/demo01/demo01_hello" scope="request"
            type="com.mars.demo01.structs01.action.HelloAction" cancellable="true">
            <forward name="show" path="/demo01/demo01_hello.jsp"></forward>
        </action>

    </action-mappings>
    
    <message-resources parameter="com.mars.demo01.structs01.ApplicationResources" />
</struts-config>
然后恢复原样，结果又好了，所以这句话是不能删的。在网上查了查，发现这是一个定义格式的东东。怎么弄的这么麻烦。

DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.LONG);
Date now = new Date(System.currentTimeMillis());
out.println(dateFormat.format(now));
%>

编译后的代码
firstTag_tag.java

[java]
public void doTag() throws javax.servlet.jsp.JspException, java.io.IOException {
    javax.servlet.jsp.PageContext _jspx_page_context = (javax.servlet.jsp.PageContext)jspContext;
    javax.servlet.http.HttpServletRequest request = (javax.servlet.http.HttpServletRequest) _jspx_page_context.getRequest();
    javax.servlet.http.HttpServletResponse response = (javax.servlet.http.HttpServletResponse) _jspx_page_context.getResponse();
    javax.servlet.http.HttpSession session = _jspx_page_context.getSession();
    javax.servlet.ServletContext application = _jspx_page_context.getServletContext();
    javax.servlet.ServletConfig config = _jspx_page_context.getServletConfig();
    javax.servlet.jsp.JspWriter out = jspContext.getOut();
    _jspInit(config);
    jspContext.getELContext().putContext(javax.servlet.jsp.JspContext.class,jspContext);

    try {
      out.write('\r');
      out.write('\n');

DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.LONG);
Date now = new Date(System.currentTimeMillis());
out.println(dateFormat.format(now));

      out.write('\r');
      out.write('\n');
    } catch( java.lang.Throwable t ) {
      if( t instanceof javax.servlet.jsp.SkipPageException )
          throw (javax.servlet.jsp.SkipPageException) t;
      if( t instanceof java.io.IOException )
          throw (java.io.IOException) t;
      if( t instanceof java.lang.IllegalStateException )
          throw (java.lang.IllegalStateException) t;
      if( t instanceof javax.servlet.jsp.JspException )
          throw (javax.servlet.jsp.JspException) t;
      throw new javax.servlet.jsp.JspException(t);
    } finally {
      jspContext.getELContext().putContext(javax.servlet.jsp.JspContext.class,super.getJspContext());
      ((org.apache.jasper.runtime.JspContextWrapper) jspContext).syncEndTagFile();
    }
}

firstTagTest_jsp.java

[java]
public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
        throws java.io.IOException, javax.servlet.ServletException {

    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;

    try {
      response.setContentType("text/html; charset=UTF-8");
      pageContext = _jspxFactory.getPageContext(this, request, response,
                  null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();

补充：Web开发 , Jsp ,