- 浏览: 293859 次
文章分类
最新评论
JSP&Servlet学习笔记----第6章
JSP与Servlet是一体两面的关系。
JSP最终还是被编译为Servlet。
<%@page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>测试</title> </head> <body> 测试 </body> </html>上面的jsp文件最终被转译为Servlet:
/* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/9.0.0.M15 * Generated at: 2017-03-02 01:55:32 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.*; public final class one_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent, org.apache.jasper.runtime.JspSourceImports { 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 static final java.util.Set<java.lang.String> _jspx_imports_packages; private static final java.util.Set<java.lang.String> _jspx_imports_classes; static { _jspx_imports_packages = new java.util.HashSet<>(); _jspx_imports_packages.add("javax.servlet"); _jspx_imports_packages.add("javax.servlet.http"); _jspx_imports_packages.add("javax.servlet.jsp"); _jspx_imports_classes = null; } private volatile javax.el.ExpressionFactory _el_expressionfactory; private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> getDependants() { return _jspx_dependants; } public java.util.Set<java.lang.String> getPackageImports() { return _jspx_imports_packages; } public java.util.Set<java.lang.String> getClassImports() { return _jspx_imports_classes; } public javax.el.ExpressionFactory _jsp_getExpressionFactory() { if (_el_expressionfactory == null) { synchronized (this) { if (_el_expressionfactory == null) { _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); } } } return _el_expressionfactory; } public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() { if (_jsp_instancemanager == null) { synchronized (this) { if (_jsp_instancemanager == null) { _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); } } } return _jsp_instancemanager; } public void _jspInit() { } 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 java.lang.String _jspx_method = request.getMethod(); if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) { response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD"); return; } final javax.servlet.jsp.PageContext pageContext; javax.servlet.http.HttpSession session = null; 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, 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("<html>\r\n"); out.write(" <head>\r\n"); out.write(" <title>测试</title>\r\n"); out.write(" </head>\r\n"); out.write("<body>\r\n"); out.write("测试\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 { if (response.isCommitted()) { out.flush(); } else { 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); } } }第一次请求JSP时,容器会进行转译、编译和加载的操作,所以第一次请求jsp,响应会很慢。
如果想做JSP初始化或者收尾操作,则可以定义jspInit()或jspDestroy()方法。
指示元素:
<%@ 指示类型 [属性="值"]* %>
指示类型有:page、include、taglib
在<%!与%>之间声明的代码都将转译为Servlet中的类成员与方法。
在<%与%>之间声明的代码(不能声明方法)转译为_jspService()方法中的代码。
在此记录个bug:
<%@page contentType="text/html;charset=UTF-8" language="java" %> <%@page import="java.util.*"%> <%@page errorPage="errPage.jsp"%> <html> <head> <title>测试</title> </head> <%! int x = 0; int z = Integer.parseInt("123qwe"); %> <body> </body> </html>并没有跳转到errPage.jsp界面?
对应的Servlet
/* * Generated by the Jasper component of Apache Tomcat * Version: Apache Tomcat/9.0.0.M15 * Generated at: 2017-03-02 07:50:01 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.*; public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase implements org.apache.jasper.runtime.JspSourceDependent, org.apache.jasper.runtime.JspSourceImports { int x = 0; int z = Integer.parseInt("123qwe"); 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 static final java.util.Set<java.lang.String> _jspx_imports_packages; private static final java.util.Set<java.lang.String> _jspx_imports_classes; static { _jspx_imports_packages = new java.util.HashSet<>(); _jspx_imports_packages.add("javax.servlet"); _jspx_imports_packages.add("java.util"); _jspx_imports_packages.add("javax.servlet.http"); _jspx_imports_packages.add("javax.servlet.jsp"); _jspx_imports_classes = null; } private volatile javax.el.ExpressionFactory _el_expressionfactory; private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager; public java.util.Map<java.lang.String,java.lang.Long> getDependants() { return _jspx_dependants; } public java.util.Set<java.lang.String> getPackageImports() { return _jspx_imports_packages; } public java.util.Set<java.lang.String> getClassImports() { return _jspx_imports_classes; } public javax.el.ExpressionFactory _jsp_getExpressionFactory() { if (_el_expressionfactory == null) { synchronized (this) { if (_el_expressionfactory == null) { _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory(); } } } return _el_expressionfactory; } public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() { if (_jsp_instancemanager == null) { synchronized (this) { if (_jsp_instancemanager == null) { _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig()); } } } return _jsp_instancemanager; } public void _jspInit() { } 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 java.lang.String _jspx_method = request.getMethod(); if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) { response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD"); return; } final javax.servlet.jsp.PageContext pageContext; javax.servlet.http.HttpSession session = null; 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, "errPage.jsp", true, 8192, true); _jspx_page_context = pageContext; application = pageContext.getServletContext(); config = pageContext.getServletConfig(); session = pageContext.getSession(); out = pageContext.getOut(); _jspx_out = out; out.write("\n"); out.write("\n"); out.write("\n"); out.write("\n"); out.write("<html>\n"); out.write(" <head>\n"); out.write(" <title>测试</title>\n"); out.write(" </head>\n"); out.write(" \n"); out.write(" \n"); out.write("<!--\n"); out.write("HTML注释\n"); out.write("-->\n"); out.write("\n"); out.write("\n"); out.write(" \n"); out.write("\n"); out.write(" \n"); out.write("\n"); out.write(" \n"); out.write("\n"); out.write(" \n"); out.write("<body>\n"); out.write("</body>\n"); out.write("</html>\n"); } catch (java.lang.Throwable t) { if (!(t instanceof javax.servlet.jsp.SkipPageException)){ out = _jspx_out; if (out != null && out.getBufferSize() != 0) try { if (response.isCommitted()) { out.flush(); } else { 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); } } }
z变量初始化就导致异常产生了,大概根本就没有调用_jspService方法?
错误处理:
1、转译过程中
例如:<%@page buffer="16"%>
buffer属性必须指定单位,如16kb
2、编译过程中(unable to comple)
例如:Some some;没有部署Some类到服务器。
此时转译可以完成(生成*.java文件,不会生成*.class文件)。
3、运行时错误(找不到资源,程序逻辑错误等)(an exception occurred processing JSP page)
例如:NullPointerException异常
相关推荐
书 名:JSP & Servlet学习笔记(第2版) 作 者:(台湾)林信良 著 出 版 社:清华大学出版社 出版时间:2012-5-1 ISBN:9787302283669 纸书页数:456页 定 价:¥ 58.00 内容简介: 本书是作者多年来...
JSP-Servlet学习笔记第2版,详细介绍了jsp和servlet,及其原理,包含大量实例
第六篇为“Web应用高级专题”,主要讲述Servlet过滤器、JSP异常处理、JSP日志、认证和安全、部署等内容;第七篇为“Web应用开发实例”,围绕一个电子商务网站,从需求分析、架构选取、数据存储、开发、测试及部署等...
{12.13.6}drop}{177}{subsection.12.13.6} {12.13.7}rename}{177}{subsection.12.13.7} {12.14}SQL脚本}{177}{section.12.14} {12.15}Transaction}{177}{section.12.15} {12.16}char与varchar2}{178}{section....
Servlet学习笔记..............212 Servlet前言.............212 第一章 Servlet Basic ........................214 第二章 Form表单.219 第三章 Servlets生命周期................222 第四章 资源访问 ..............
Servlet学习笔记..............212 Servlet前言.............212 第一章 Servlet Basic ........................214 第二章 Form表单.219 第三章 Servlets生命周期................222 第四章 资源访问 ..............
再看第二本《java核心技术卷1-基础知识》,bruce eckel推荐的入门书籍。 第三本是《java核心技术卷2-高级特性》。 第四本是bruce eckel本人编写的《java编程思想》。...第六本是《head first ejb》。
第六章:J2EE专题学习 167 6.1:EJB 167 6.2:JMS 172 6.3:Socket 182 6.4:WebService 189 6.5:集群分布式应用(以JBOSS为例) 190 6.6:JNLP原理及应用: 190 6.7:Log4原理及应用: 191 6.8:JFreeChat原理及应用: 191 ...
第一章 1.Java 编程语言刚开始 Oak 橡树 办公室外 已被注册 边喝咖啡边讨论名称 2.动态加载类别文档、字符串池(String Pool)等特性为节省内存而设计 3.jdk java development kit java 开发工具集 java se 平台...
以“%”开头,[第几个数值$][flags][宽度][.精确度][格式] printf()的引入是为了照顾c语言程序员的感情需要 格式化输出 Formatter;格式化输入 Scanner;正则表达式 输出格式控制: 转义符: \ddd 1到3位8...