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JSP page指令

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09/19
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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);
}
}
}