安装配置好jdk。tomcat，我用的版本号是7.0.54，我放在C:serverapache-tomcat-7.0.54下，
CATALINA_BASE：C:serverapache-tomcat-7.0.54
CATALINA_HOME：C:serverapache-tomcat-7.0.54
也能够在Path以下加入配置 ;C:serverapache-tomcat-7.0.54in ，这样就能够在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,文件文件夹例如以下：
web.xml这个文件能够在C:serverapache-tomcat-7.0.54webappsexamplesWEB-INF下找到，加入默认的页面即可了（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>
然后就是写jsp页面了（index.jsp）
<%@ 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，我们能够查看到编译后的代码。详细地址在C:serverapache-tomcat-7.0.54work文件夹下：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("
");
out.write("<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
");
out.write("<html>
");
out.write("<head>
");
out.write("<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
");
out.write("<title>java web</title>
");
out.write("</head>
");
out.write("<body>
");
out.write(" Java Web HelloWorld<br />
");
out.write(" ");
out.println(new java.util.Date());
out.write('
');
out.write('
');
out.write(' ');
out.write('
');
out.write('
');
out.write(' ');
out.println(count++);
out.write('
');
out.write('
');
out.write(' ');
out.print(info() );
out.write("
");
out.write("
");
out.write("</body>
");
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);
}
}
}
能够看到count被转化成了全局变量。所以当我们开启第二个浏览器刷新时，值会在前一个浏览器基础之上不断叠加。
Java类中能够看到有Init，destroy，service这些我们在Servlet里面看到的方法。事实上Jsp本质上也就是一个Servlet，是一个Java类。
而这一个转换过程须要的Web容器Tomcat起到了居功至伟的作用。终于对应的页面会以HTML形式展现给浏览器。
对于Java Web应用而言，WEB-INF是一个特殊的目录，Web容器会包括该目录的内容，client浏览器无法訪问WEB-INF路径下的不论什么内容。
<%%> 标签是JSP差别HTML标签的一个重要标志，里面能够写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，假设没有!号。将编译报错。（等于说把这段代码搁在解析方法里面了，由于不能有方法中的方法啊~）