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JSP page指令

本文轉載自   查看原文   2015-10-20 08:31   2091    JSP

JSP page指令：

JSP文件：

<%@ page language="java"%>
<%@ page import="java.util.*"%>
<%@ page isThreadSafe="false"%>
<%@ page contentType="text/html; charset=UTF-8"%>
<%@ page isELIgnored="true"%>
<%@ page isErrorPage="true"%>
<%@ page errorPage="index0051.jsp"%>
<!-- %@ page extends="org.apache.jsp"% -->
<%@ page session="false"%>
<%@ page buffer="none"%>
<%@ page autoFlush="true"%>
<%@ page info="infotext"%>
<%@ page pageEncoding="UTF-8"%>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
    pageContext.setAttribute("pca", "pageContextAttribute");
    //session.setAttribute("s", "session");
%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>005index</title>
</head>
<body>
    <p>Page指令</p>
    <p>Page指令可以在頁面內隨便放置，最好放在頁首；</p>
    <p>language屬性不寫可以，寫成別的會無法編譯，異常為:org.apache.jasper.JasperException: /index005.jsp (line: 1, column: 2) Page directive: invalid language attribute</p>
    <%@ page import="a.b.*"%>
    <p>import屬性，寫了之后會自動添加到servlet的import語句中，但不進行包存在性的檢查；反編譯生成的class中就沒有無效的包；</p>
    <p>isThreadSafe問你的應用是否是線程安全的，缺省為true，表示應用是線程安全的，可以同時響應多個請求；如果設置為false，生成的servlet會實現javax.servlet.SingleThreadModel線程，那么一次只能處理一個用戶請求；</p>
    <p>${pageScope.pca }</p>
    <p>isELIgnored忽略el表達式</p>
    <p>errorPage="relativeURL" 設置處理異常事件的JSP文件。 isErrorPage="true | false" 設置此頁是否為出錯頁，如果被設置為true,你就能使用exception對象.</p>
    <p>extends="package.class" 標明JSP編譯時需要加入的Java Class的全名，但是得慎重的使用它，它會限制JSP的編譯能力.寫成別的就無法轉換了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>
    <p>session="false"就沒有session對象了；</p>
    <p>contentType屬性設置發送到客戶端文檔的響應報頭的MIME類型和字符編碼。多個使用;號分開。 pageEncodeing屬性只用於更改字符編碼。</p>
    <p>buffer屬性指定out對象(JspWriter)使用的緩沖區大小，以kb為單位，默認8kb。 none表示不使用緩沖區。這樣要求設置報頭或狀態代碼的jsp元素要出現在文件的頂部，任何HTML內容之前。 autoFlush屬性控制當緩沖區滿了后，是自動清空輸出緩沖區(默認true)，還是在緩沖區溢出后拋出異常(false)。
        在buffer=none的時候，autoFlush=false是錯誤的。</p>
    <p>定義一個可以在servlet中通過getServletInfo方法獲取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info屬性指定的String。</p>
</body>
</html>

 

JSP轉換的java文件：

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.35
 * Generated at: 2015-10-20 00:27:17 UTC
 * Note: The last modified time of this file was set to
 *       the last modified time of the source file after
 *       generation to assist with modification tracking.
 */
package org.apache.jsp;

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

public final class index005_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent,
                 javax.servlet.SingleThreadModel {

  public java.lang.String getServletInfo() {
    return "infotext";
  }

  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();

  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;

  private javax.el.ExpressionFactory _el_expressionfactory;
  private org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  }

  public void _jspInit() {
    _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
  }

  public void _jspDestroy() {
  }

  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;
    java.lang.Throwable exception = org.apache.jasper.runtime.JspRuntimeLibrary.getThrowable(request);
    if (exception != null) {
      response.setStatus(javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
    }
    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,
                  "index0051.jsp", false, 0, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("<!-- %@ page extends=\"org.apache.jsp\"% -->\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");

    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
    pageContext.setAttribute("pca", "pageContextAttribute");
    //session.setAttribute("s", "session");

      out.write("\r\n");
      out.write("<!DOCTYPE html>\r\n");
      out.write("<html>\r\n");
      out.write("<head>\r\n");
      out.write("<meta charset=\"UTF-8\">\r\n");
      out.write("<title>005index</title>\r\n");
      out.write("</head>\r\n");
      out.write("<body>\r\n");
      out.write("\t<p>Page指令</p>\r\n");
      out.write("\t<p>Page指令可以在頁面內隨便放置，最好放在頁首；</p>\r\n");
      out.write("\t<p>language屬性不寫可以，寫成別的會無法編譯，異常為:org.apache.jasper.JasperException: /index005.jsp (line: 1, column: 2) Page directive: invalid language attribute</p>\r\n");
      out.write("\t\r\n");
      out.write("\t<p>import屬性，寫了之后會自動添加到servlet的import語句中，但不進行包存在性的檢查；反編譯生成的class中就沒有無效的包；</p>\r\n");
      out.write("\t<p>isThreadSafe問你的應用是否是線程安全的，缺省為true，表示應用是線程安全的，可以同時響應多個請求；如果設置為false，生成的servlet會實現javax.servlet.SingleThreadModel線程，那么一次只能處理一個用戶請求；</p>\r\n");
      out.write("\t<p>${pageScope.pca }</p>\r\n");
      out.write("\t<p>isELIgnored忽略el表達式</p>\r\n");
      out.write("\t<p>errorPage=\"relativeURL\" 設置處理異常事件的JSP文件。 isErrorPage=\"true | false\" 設置此頁是否為出錯頁，如果被設置為true,你就能使用exception對象.</p>\r\n");
      out.write("\t<p>extends=\"package.class\" 標明JSP編譯時需要加入的Java Class的全名，但是得慎重的使用它，它會限制JSP的編譯能力.寫成別的就無法轉換了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>\r\n");
      out.write("\t<p>session=\"false\"就沒有session對象了；</p>\r\n");
      out.write("\t<p>contentType屬性設置發送到客戶端文檔的響應報頭的MIME類型和字符編碼。多個使用;號分開。 pageEncodeing屬性只用於更改字符編碼。</p>\r\n");
      out.write("\t<p>buffer屬性指定out對象(JspWriter)使用的緩沖區大小，以kb為單位，默認8kb。 none表示不使用緩沖區。這樣要求設置報頭或狀態代碼的jsp元素要出現在文件的頂部，任何HTML內容之前。 autoFlush屬性控制當緩沖區滿了后，是自動清空輸出緩沖區(默認true)，還是在緩沖區溢出后拋出異常(false)。\r\n");
      out.write("\t\t在buffer=none的時候，autoFlush=false是錯誤的。</p>\r\n");
      out.write("\t<p>定義一個可以在servlet中通過getServletInfo方法獲取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info屬性指定的String。</p>\r\n");
      out.write("</body>\r\n");
      out.write("</html>\r\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.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);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

 

反編譯class文件：

package org.apache.jsp;

import java.io.IOException;
import java.util.Map;
import javax.el.ExpressionFactory;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.SingleThreadModel;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspApplicationContext;
import javax.servlet.jsp.JspFactory;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.SkipPageException;
import org.apache.jasper.runtime.HttpJspBase;
import org.apache.jasper.runtime.InstanceManagerFactory;
import org.apache.jasper.runtime.JspRuntimeLibrary;
import org.apache.jasper.runtime.JspSourceDependent;
import org.apache.tomcat.InstanceManager;

public final class index005_jsp extends HttpJspBase
  implements JspSourceDependent, SingleThreadModel
{
  private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();
  private static Map<String, Long> _jspx_dependants;
  private ExpressionFactory _el_expressionfactory;
  private InstanceManager _jsp_instancemanager;

  public String getServletInfo()
  {
    return "infotext";
  }

  public Map<String, Long> getDependants()
  {
    return _jspx_dependants;
  }

  public void _jspInit() {
    this._el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
    this._jsp_instancemanager = InstanceManagerFactory.getInstanceManager(getServletConfig());
  }

  public void _jspDestroy()
  {
  }

  public void _jspService(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
  {
    Throwable exception = JspRuntimeLibrary.getThrowable(request);
    if (exception != null) {
      response.setStatus(500);
    }

    JspWriter out = null;

    JspWriter _jspx_out = null;
    PageContext _jspx_page_context = null;
    try
    {
      response.setContentType("text/html; charset=UTF-8");
      PageContext pageContext = _jspxFactory.getPageContext(this, request, response, 
        "index0051.jsp", false, 0, true);
      _jspx_page_context = pageContext;
      pageContext.getServletContext();
      pageContext.getServletConfig();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("<!-- %@ page extends=\"org.apache.jsp\"% -->\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");
      out.write("\r\n");

      String path = request.getContextPath();
      new StringBuilder(String.valueOf(request.getScheme())).append("://").append(request.getServerName()).append(":").append(request.getServerPort()).append(path).append("/").toString();
      pageContext.setAttribute("pca", "pageContextAttribute");

      out.write("\r\n");
      out.write("<!DOCTYPE html>\r\n");
      out.write("<html>\r\n");
      out.write("<head>\r\n");
      out.write("<meta charset=\"UTF-8\">\r\n");
      out.write("<title>005index</title>\r\n");
      out.write("</head>\r\n");
      out.write("<body>\r\n");
      out.write("\t<p>Page指令</p>\r\n");
      out.write("\t<p>Page指令可以在頁面內隨便放置，最好放在頁首；</p>\r\n");
      out.write("\t<p>language屬性不寫可以，寫成別的會無法編譯，異常為:org.apache.jasper.JasperException: /index005.jsp (line: 1, column: 2) Page directive: invalid language attribute</p>\r\n");
      out.write("\t\r\n");
      out.write("\t<p>import屬性，寫了之后會自動添加到servlet的import語句中，但不進行包存在性的檢查；反編譯生成的class中就沒有無效的包；</p>\r\n");
      out.write("\t<p>isThreadSafe問你的應用是否是線程安全的，缺省為true，表示應用是線程安全的，可以同時響應多個請求；如果設置為false，生成的servlet會實現javax.servlet.SingleThreadModel線程，那么一次只能處理一個用戶請求；</p>\r\n");
      out.write("\t<p>${pageScope.pca }</p>\r\n");
      out.write("\t<p>isELIgnored忽略el表達式</p>\r\n");
      out.write("\t<p>errorPage=\"relativeURL\" 設置處理異常事件的JSP文件。 isErrorPage=\"true | false\" 設置此頁是否為出錯頁，如果被設置為true,你就能使用exception對象.</p>\r\n");
      out.write("\t<p>extends=\"package.class\" 標明JSP編譯時需要加入的Java Class的全名，但是得慎重的使用它，它會限制JSP的編譯能力.寫成別的就無法轉換了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>\r\n");
      out.write("\t<p>session=\"false\"就沒有session對象了；</p>\r\n");
      out.write("\t<p>contentType屬性設置發送到客戶端文檔的響應報頭的MIME類型和字符編碼。多個使用;號分開。 pageEncodeing屬性只用於更改字符編碼。</p>\r\n");
      out.write("\t<p>buffer屬性指定out對象(JspWriter)使用的緩沖區大小，以kb為單位，默認8kb。 none表示不使用緩沖區。這樣要求設置報頭或狀態代碼的jsp元素要出現在文件的頂部，任何HTML內容之前。 autoFlush屬性控制當緩沖區滿了后，是自動清空輸出緩沖區(默認true)，還是在緩沖區溢出后拋出異常(false)。\r\n");
      out.write("\t\t在buffer=none的時候，autoFlush=false是錯誤的。</p>\r\n");
      out.write("\t<p>定義一個可以在servlet中通過getServletInfo方法獲取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info屬性指定的String。</p>\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 (IOException localIOException) { }
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }

      _jspxFactory.releasePageContext(_jspx_page_context); } finally { _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

 


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