安装配置好jdk，tomcat，我用的版本是7.0.54，我放在C:\server\apache-tomcat-7.0.54下，
CATALINA_BASE：C:\server\apache-tomcat-7.0.54
CATALINA_HOME：C:\server\apache-tomcat-7.0.54
也可以在Path下面添加配置 ;C:\server\apache-tomcat-7.0.54\bin ，这样就可以在cmd下直接输入startup启动服务器了。
背景：运用web容器tomcat和jsp Servlet 技术建立第一个Hello,文件目录如下：
web.xml这个文件可以在C:\server\apache-tomcat-7.0.54\webapps\examples\WEB-INF下找到，添加默认的页面就行了（默认是index.html,index.htm,index.jsp）
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0"
metadata-complete="true">
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>java web</title>
</head>
<body>
Java Web HelloWorld<br />
<% out.println(new java.util.Date());%>
<%!
public int count;
public String info(){
return "hello";
}
%>
<%
out.println(count++);
%>
<%=info() %>
</body>
</html> 通过Tomcat容器，我们可以查看到编译后的代码，具体地址在C:\server\apache-tomcat-7.0.54\work目录下：package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
public int count;
public String info(){
return "hello";
}
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;
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("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\r\n");
out.write("<html>\r\n");
out.write("<head>\r\n");
out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">\r\n");
out.write("<title>java web</title>\r\n");
out.write("</head>\r\n");
out.write("<body>\r\n");
out.write("\tJava Web HelloWorld<br />\r\n");
out.write("\t");
out.println(new java.util.Date());
out.write('\r');
out.write('\n');
out.write(' ');
out.write('\r');
out.write('\n');
out.write(' ');
out.println(count++);
out.write('\r');
out.write('\n');
out.write(' ');
out.print(info() );
out.write("\r\n");
out.write("\r\n");
out.write("</body>\r\n");
out.write("</html>");
} 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);
}
}
}
Java类中可以看到有Init，destroy，service这些我们在Servlet里面看到的方法，其实Jsp本质上也就是一个Servlet，是一个Java类。而这一个转换过程需要的Web容器Tomcat起到了居功至伟的作用。最终相应的页面会以HTML形式展现给浏览器。对于Java Web应用而言，WEB-INF是一个特殊的文件夹，Web容器会包含该文件夹的内容，客户端浏览器无法访问WEB-INF路径下的任何内容。
<%%> 标签是JSP区别HTML标签的一个重要标志，里面可以写Java代码，构成JSP的动态部分。
<%=%>是JSP的输出表达式，输出表达式后不能有分号。
<:%!%>是声明标签，编译过后我们看到他在最外层，如果没有!号，将编译报错。（等于说把这段代码搁在解析方法里面了，因为不能有方法中的方法啊~）
【读书札记】建立第一个Web项目,布布扣,bubuko.com
原文地址：http://blog.csdn.net/pearyangyang/article/details/38373451
