标签：res als oaf err bsp iter 中间 ant ati
jsp标签涉及的类层次结构如图：
jsp标签定义步骤：
1)创建标签处理类
public class MyTag extends TagSupport{
//
}
2)tld文件定义
3)引入标签
<%@ taglib prefix="my" uri="/my-tags" %>
<my:mytag date="yyyy-MM-dd HH-mm-ss" first=" {这是我第一个属性}">
jsp tag原理分析
public final class myTag_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent { private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory(); private static java.util.List _jspx_dependants; static { _jspx_dependants = new java.util.ArrayList(1); _jspx_dependants.add("/WEB-INF/myTag.tld"); } //为所有的定制标签定义处理器池类的引用 private org.apache.jasper.runtime.TagHandlerPool _005fjspx_005ftagPool_005fmy_005fmytag_0026_005ffirst_005fdate; private javax.el.ExpressionFactory _el_expressionfactory; private org.apache.AnnotationProcessor _jsp_annotationprocessor; ............................... //为处理器池类赋值 public void _jspInit() { _005fjspx_005ftagPool_005fmy_005fmytag_0026_005ffirst_005fdate = org.apache.jasper.runtime.TagHandlerPool.getTagHandlerPool(getServletConfig()); _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor.class.getName()); }
public void _jspService(HttpServletRequest request, HttpServletResponse response) throws java.io.IOException, ServletException { PageContext pageContext = null; HttpSession session = null; ServletContext application = null; ServletConfig config = null; JspWriter out = null; Object page = this; JspWriter _jspx_out = null; 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(); config = pageContext.getServletConfig(); session = pageContext.getSession(); out = pageContext.getOut(); _jspx_out = out; out.write("\r\n"); out.write("\r\n"); String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; ....................................... out.write(" <body>\r\n"); out.write(" This is my JSP page. <br>\r\n"); out.write(" \r\n"); out.write(" "); if (_jspx_meth_my_005fmytag_005f0(_jspx_page_context)) //标签的处理，请往下看方法的实现。 return; out.write("\r\n"); out.write(" \r\n"); out.write(" \r\n"); out.write(" </body>\r\n"); out.write("</html>\r\n"); } catch (Throwable t) { if (!(t instanceof SkipPageException)){ out = _jspx_out; if (out != null && out.getBufferSize() != 0) try { out.clearBuffer(); } catch (java.io.IOException e) {} if (_jspx_page_context != null) _jspx_page_context.handlePageException(t); } } finally { _jspxFactory.releasePageContext(_jspx_page_context); } }
//真正处理标签<my:myTag >方法 private boolean _jspx_meth_my_005fmytag_005f0(PageContext _jspx_page_context) throws Throwable { PageContext pageContext = _jspx_page_context; JspWriter out = _jspx_page_context.getOut(); // my:mytag com.common.tag.MyTag _jspx_th_my_005fmytag_005f0 = (com.common.tag.MyTag) _005fjspx_005ftagPool_005fmy_005fmytag_0026_005ffirst_005fdate.get(com.common.tag.MyTag.class); //JSP容器在调用doStartTag或者doEndTag方法前，会先调用setPageContext和setParent方法，设置pageContext和parent，而且也调用setFiled()方法设置标签的相关属性; _jspx_th_my_005fmytag_005f0.setPageContext(_jspx_page_context); _jspx_th_my_005fmytag_005f0.setParent(null); // /index.jsp(19,4) name = date type = java.lang.String reqTime = false required = false fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null _jspx_th_my_005fmytag_005f0.setDate("yyyy-MM-dd HH-mm-ss"); // /index.jsp(19,4) name = first type = java.lang.String reqTime = false required = false fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null _jspx_th_my_005fmytag_005f0.setFirst(" {这是我第一个属性}"); int _jspx_eval_my_005fmytag_005f0 = _jspx_th_my_005fmytag_005f0.doStartTag(); // JSP容器处理 //到自定义标签的起始标志，就会调用doStartTag()方法 if (_jspx_eval_my_005fmytag_005f0 != javax.servlet.jsp.tagext.Tag.SKIP_BODY) { //如果doStartTag()方 // 法返回值不是Tag.SKIP_BODY就执行标签体 do { out.write("\r\n"); out.write(" \r\n"); out.write(" 中间体执行吧。\r\n"); out.write(" \r\n"); out.write(" "); int evalDoAfterBody = _jspx_th_my_005fmytag_005f0.doAfterBody(); //看到这里你应该知道 //tomcat是怎么处理doAfterBody(); 了吧。 if (evalDoAfterBody != javax.servlet.jsp.tagext.BodyTag.EVAL_BODY_AGAIN) //如果doAfterBody()返 //回值是EVAL_BODY_AGAIN，则再次执行方法体和doAfterBody()方法， // 直到doAfterBody()返 //回值为SKIP_BODY才跳出循环 break; } while (true); }
//do{}while(true)无论doAfterBody()返回值如何都会执行方法体一次 if (_jspx_th_my_005fmytag_005f0.doEndTag() == javax.servlet.jsp.tagext.Tag.SKIP_PAGE) { _005fjspx_005ftagPool_005fmy_005fmytag_0026_005ffirst_005fdate.reuse(_jspx_th_my_005fmytag_005f0); return true; } _005fjspx_005ftagPool_005fmy_005fmytag_0026_005ffirst_005fdate.reuse(_jspx_th_my_005fmytag_005f0); return false; }
}
标签：res als oaf err bsp iter 中间 ant ati
原文地址：http://www.cnblogs.com/liluredhat/p/6759674.html
