在Jsp中调用图片、JS脚本等，针对取得的路径有两种调用方式：
1、放入Body中生成绝对路径（不建议）
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>image调用</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<h1>图片访问</h1>
<div>
<img alt="图片" src="<%=basePath%>/image/a.png">
</div>
</body>
</html>
2、在Head中指定，Body中使用相对路径（建议）
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>image调用</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<!-- base需要放到head中 -->
<base href=" <%=basePath%>">
</head>
<body>
<h1>图片访问</h1>
<div>
<img alt="图片" src="data:image/a.png">
</div>
</body>
</html>
转载自：https://www.cnblogs.com/maocs/p/4256302.html
getRequestURI,getRequestURL的区别
test1.jsp=======================
<a href ="test.jsp?p=fuck">跳转到test2</a>
test2.jsp=======================
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
out.println("basePath:"+basePath);
out.println("<br/>");
out.println("getContextPath:"+request.getContextPath());
out.println("<br/>");
out.println("getServletPath:"+request.getServletPath());
out.println("<br/>");
out.println("getRequestURI:"+request.getRequestURI());
out.println("<br/>");
out.println("getRequestURL:"+request.getRequestURL());
out.println("<br/>");
out.println("getRealPath:"+request.getRealPath("/"));
out.println("<br/>");
out.println("getServletContext().getRealPath:"+getServletContext().getRealPath("/"));
out.println("<br/>");
out.println("getQueryString:"+request.getQueryString());
%>
显示结果：
basePath:http://localhost:8080/test/
getContextPath:/test
getServletPath:/test.jsp
getRequestURI:/test/test.jsp
getRequestURL:http://localhost:8080/test/test.jsp
getRealPath:D:\Tomcat 6.0\webapps\test\
getServletContext().getRealPath:D:\Tomcat 6.0\webapps\test\
getQueryString:p=fuck
在一些应用中，未登录用户请求了必须登录的资源时，提示用户登录，此时要记住用户访问的当前页面的URL，当他登录成功后根据记住的URL跳回用户最后访问的页面：
String lastAccessUrl = request.getRequestURL() + "?" + request.getQueryString();
以上转自：http://www.cnblogs.com/JemBai/archive/2010/11/10/1873764.html