jspweb里面用到的servlet跳转页面的方法
使用的jar包只有
commons-lang3-3.5.jar
运行时,tomcat会先根据web.xml里面的信息,查找servlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>servlet</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>servlet</servlet-name>
<servlet-class>com.javaweb.action.Servlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>servlet</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>
</web-app>
<servlet> 就是你注册的servlet和他的物理地址
<servlet-mapping>servlet的相对地址,就是在.jsp中怎么用
然后就是根据欢迎页面index.jsp等待用户操作
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();// 获得当前的项目根目录路径
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path;
//完整路径
%>
<!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>这是首页</title>
</head>
<body>
<table border=0 cellpadding=0 cellspacing=0 style="margin:auto;border-collapse:separate; border-spacing:10px;">
<tr>
<td>
servlet根目录路径:<%out.print(path);%>
</td>
</tr>
<tr>
<td>
servlet完整路径:<%out.print(basePath);%>
</td>
</tr>
<tr>
<td>
<!--后缀名是.do的直接根据目录找到first方法-->
<a href="<%=basePath%>/first.do">第一的英文</a>
</td>
</tr>
<tr>
<td>
<!--?的是-->
<a href="<%=basePath%>/.do?op=second">第二的英文</a>
</td>
</tr>
<tr>
<td>
<!--触发?的else选项,常用来放错误信息-->
<a href="<%=basePath%>/.do?op=WOSUIBIANDADE">第三的英文</a>
</td>
</tr>
</table>
</body>
</html>
servlet的具体响应
package com.javaweb.action;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang3.StringUtils;
public class Servlet extends HttpServlet{
/**
* 用于版本控制
*/
private static final long serialVersionUID = -2357925750878300415L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// TODO Auto-generated method stub
//纯碎是用来判断有没有错误
String url=req.getServletPath();
String method=url.substring(1,url.lastIndexOf("."));
try {
Method met=getClass().getDeclaredMethod(method, HttpServletRequest.class,HttpServletResponse.class);
try {
met.invoke(this, req,resp);
} catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
e.printStackTrace();
}
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
}
//使用?跳转页面
req.setCharacterEncoding("UTF-8");
String op=req.getParameter("op");
if(StringUtils.isNotBlank(op)){
if("second".equalsIgnoreCase(op)){
second(req, resp);
}else{
PrintWriter out=resp.getWriter();//调用窗口
out.println("THIRD");
}
}
}
public void first(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("first.jsp");
}
public void second(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("second.jsp");
}
}
显然用?的方法和用.do的方法都能实现同样的功能
但是在大量方法同时存在的时候?方法可以用于区分不同方面的方法
req.getParameter("login");
req.getParameter("logout");....
结果