jsp自定义标签的执行流程

1、客户端访问jsp页面，遇到自定义的标签；

2、初始化自定义标签对应的标签处理器，并通过setPageContext()方法，设置pageContext给标签对象；

3、看标签是否有父标签，如果有，则实例化父标签对应的处理器对象。并通过setParent()方法设置给标签对象；

4、调用doStartTag()方法

5、执行标签体

6、调用doEndTag()方法

7、释放资源

8、执行标签体后面的jsp相关的代码

 

以下是tomcat下面运行jsp后的java代码

package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;

public final class index_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/simpletag/simple.tld");
  }

  private javax.el.ExpressionFactory _el_expressionfactory;
  private org.apache.AnnotationProcessor _jsp_annotationprocessor;

  public Object getDependants() {
    return _jspx_dependants;
  }

  public void _jspInit() {
    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor.class.getName());
  }

  public void _jspDestroy() {
  }

  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=ISO-8859-1");
      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("\r\n");
      out.write("\r\n");
      out.write("<html>\r\n");
      out.write("  <head>\r\n");
      out.write("    <title>My JSP 'index.jsp' starting page</title>\r\n");
      out.write("  </head>\r\n");
      out.write("  \r\n");
      out.write("  <body>\r\n");
      out.write("  ");
 
  	String ip = request.getRemoteAddr();
  	out.print(ip);
   
      out.write('\r');
      out.write('\n');
      out.write(' ');
      if (_jspx_meth_simple_005fsimple5_005f0(_jspx_page_context))
        return;
      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);
    }
  }

  private boolean _jspx_meth_simple_005fsimple5_005f0(PageContext _jspx_page_context)
          throws Throwable {
    PageContext pageContext = _jspx_page_context;
    JspWriter out = _jspx_page_context.getOut();
    //  simple:simple5
    www.itcast.cn.Simple5 _jspx_th_simple_005fsimple5_005f0 = new www.itcast.cn.Simple5();
    org.apache.jasper.runtime.AnnotationHelper.postConstruct(_jsp_annotationprocessor, _jspx_th_simple_005fsimple5_005f0);
    _jspx_th_simple_005fsimple5_005f0.setJspContext(_jspx_page_context);
    // /index.jsp(18,1) name = name type = null reqTime = true required = true fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null
    _jspx_th_simple_005fsimple5_005f0.setName(9);
    _jspx_th_simple_005fsimple5_005f0.setJspBody(new index_jspHelper( 0, _jspx_page_context, _jspx_th_simple_005fsimple5_005f0, null));
    _jspx_th_simple_005fsimple5_005f0.doTag();
    org.apache.jasper.runtime.AnnotationHelper.preDestroy(_jsp_annotationprocessor, _jspx_th_simple_005fsimple5_005f0);
    return false;
  }

  private class index_jspHelper
      extends org.apache.jasper.runtime.JspFragmentHelper
  {
    private javax.servlet.jsp.tagext.JspTag _jspx_parent;
    private int[] _jspx_push_body_count;

    public index_jspHelper( int discriminator, JspContext jspContext, javax.servlet.jsp.tagext.JspTag _jspx_parent, int[] _jspx_push_body_count ) {
      super( discriminator, jspContext, _jspx_parent );
      this._jspx_parent = _jspx_parent;
      this._jspx_push_body_count = _jspx_push_body_count;
    }
    public boolean invoke0( JspWriter out ) 
      throws Throwable
    {
      out.write("fdfd");
      return false;
    }
    public void invoke( java.io.Writer writer )
      throws JspException
    {
      JspWriter out = null;
      if( writer != null ) {
        out = this.jspContext.pushBody(writer);
      } else {
        out = this.jspContext.getOut();
      }
      try {
        this.jspContext.getELContext().putContext(JspContext.class,this.jspContext);
        switch( this.discriminator ) {
          case 0:
            invoke0( out );
            break;
        }
      }
      catch( Throwable e ) {
        if (e instanceof SkipPageException)
            throw (SkipPageException) e;
        throw new JspException( e );
      }
      finally {
        if( writer != null ) {
          this.jspContext.popBody();
        }
      }
    }
  }
}