JSP page指令

时间：2023-03-09 15:08:35
JSP page指令

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指令可以在页面内随便放置，最好放在页首；</p>

    <p>language属性不写可以，写成别的会无法编译，异常为:org.apache.jasper.JasperException: /index005.jsp (line: 1, column: 2) Page directive: invalid language attribute</p>

    <%@ page import="a.b.*"%>

    <p>import属性，写了之后会自动添加到servlet的import语句中，但不进行包存在性的检查；反编译生成的class中就没有无效的包；</p>

    <p>isThreadSafe问你的应用是否是线程安全的，缺省为true，表示应用是线程安全的，可以同时响应多个请求；如果设置为false，生成的servlet会实现javax.servlet.SingleThreadModel线程，那么一次只能处理一个用户请求；</p>

    <p>${pageScope.pca }</p>

    <p>isELIgnored忽略el表达式</p>

    <p>errorPage="relativeURL" 设置处理异常事件的JSP文件。 isErrorPage="true | false" 设置此页是否为出错页，如果被设置为true,你就能使用exception对象.</p>

    <p>extends="package.class" 标明JSP编译时需要加入的Java Class的全名，但是得慎重的使用它，它会限制JSP的编译能力.写成别的就无法转换了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>

    <p>session="false"就没有session对象了；</p>

    <p>contentType属性设置发送到客户端文档的响应报头的MIME类型和字符编码。多个使用;号分开。 pageEncodeing属性只用于更改字符编码。</p>

    <p>buffer属性指定out对象(JspWriter)使用的缓冲区大小，以kb为单位，默认8kb。 none表示不使用缓冲区。这样要求设置报头或状态代码的jsp元素要出现在文件的顶部，任何HTML内容之前。 autoFlush属性控制当缓冲区满了后，是自动清空输出缓冲区(默认true)，还是在缓冲区溢出后抛出异常(false)。

        在buffer=none的时候，autoFlush=false是错误的。</p>

    <p>定义一个可以在servlet中通过getServletInfo方法获取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info属性指定的String。</p>

</body>

</html>

JSP转换的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指令可以在页面内随便放置，最好放在页首；</p>\r\n");

      out.write("\t<p>language属性不写可以，写成别的会无法编译，异常为: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属性，写了之后会自动添加到servlet的import语句中，但不进行包存在性的检查；反编译生成的class中就没有无效的包；</p>\r\n");

      out.write("\t<p>isThreadSafe问你的应用是否是线程安全的，缺省为true，表示应用是线程安全的，可以同时响应多个请求；如果设置为false，生成的servlet会实现javax.servlet.SingleThreadModel线程，那么一次只能处理一个用户请求；</p>\r\n");

      out.write("\t<p>${pageScope.pca }</p>\r\n");

      out.write("\t<p>isELIgnored忽略el表达式</p>\r\n");

      out.write("\t<p>errorPage=\"relativeURL\" 设置处理异常事件的JSP文件。 isErrorPage=\"true | false\" 设置此页是否为出错页，如果被设置为true,你就能使用exception对象.</p>\r\n");

      out.write("\t<p>extends=\"package.class\" 标明JSP编译时需要加入的Java Class的全名，但是得慎重的使用它，它会限制JSP的编译能力.写成别的就无法转换了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>\r\n");

      out.write("\t<p>session=\"false\"就没有session对象了；</p>\r\n");

      out.write("\t<p>contentType属性设置发送到客户端文档的响应报头的MIME类型和字符编码。多个使用;号分开。 pageEncodeing属性只用于更改字符编码。</p>\r\n");

      out.write("\t<p>buffer属性指定out对象(JspWriter)使用的缓冲区大小，以kb为单位，默认8kb。 none表示不使用缓冲区。这样要求设置报头或状态代码的jsp元素要出现在文件的顶部，任何HTML内容之前。 autoFlush属性控制当缓冲区满了后，是自动清空输出缓冲区(默认true)，还是在缓冲区溢出后抛出异常(false)。\r\n");

      out.write("\t\t在buffer=none的时候，autoFlush=false是错误的。</p>\r\n");

      out.write("\t<p>定义一个可以在servlet中通过getServletInfo方法获取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info属性指定的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);

    }

  }

}

反编译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指令可以在页面内随便放置，最好放在页首；</p>\r\n");

      out.write("\t<p>language属性不写可以，写成别的会无法编译，异常为: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属性，写了之后会自动添加到servlet的import语句中，但不进行包存在性的检查；反编译生成的class中就没有无效的包；</p>\r\n");

      out.write("\t<p>isThreadSafe问你的应用是否是线程安全的，缺省为true，表示应用是线程安全的，可以同时响应多个请求；如果设置为false，生成的servlet会实现javax.servlet.SingleThreadModel线程，那么一次只能处理一个用户请求；</p>\r\n");

      out.write("\t<p>${pageScope.pca }</p>\r\n");

      out.write("\t<p>isELIgnored忽略el表达式</p>\r\n");

      out.write("\t<p>errorPage=\"relativeURL\" 设置处理异常事件的JSP文件。 isErrorPage=\"true | false\" 设置此页是否为出错页，如果被设置为true,你就能使用exception对象.</p>\r\n");

      out.write("\t<p>extends=\"package.class\" 标明JSP编译时需要加入的Java Class的全名，但是得慎重的使用它，它会限制JSP的编译能力.写成别的就无法转换了。org.apache.jasper.JasperException: Unable to compile class for JSP:</p>\r\n");

      out.write("\t<p>session=\"false\"就没有session对象了；</p>\r\n");

      out.write("\t<p>contentType属性设置发送到客户端文档的响应报头的MIME类型和字符编码。多个使用;号分开。 pageEncodeing属性只用于更改字符编码。</p>\r\n");

      out.write("\t<p>buffer属性指定out对象(JspWriter)使用的缓冲区大小，以kb为单位，默认8kb。 none表示不使用缓冲区。这样要求设置报头或状态代码的jsp元素要出现在文件的顶部，任何HTML内容之前。 autoFlush属性控制当缓冲区满了后，是自动清空输出缓冲区(默认true)，还是在缓冲区溢出后抛出异常(false)。\r\n");

      out.write("\t\t在buffer=none的时候，autoFlush=false是错误的。</p>\r\n");

      out.write("\t<p>定义一个可以在servlet中通过getServletInfo方法获取的字符串。 jsp容器做的是在servlet中生成getServletInfo方法返回info属性指定的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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