轉發與重定向的區別
前言：之前寫了幾篇JSP的博客，現在又回過頭來看Servlet，溫故而知新，再回顧回顧，總會有收獲的。以前學習Servlet感覺內容很多，現在看的時候，其實也沒多少東西，只需知道Servlet的生命周期，Servlet的實現方式，ServletContext作用域，接收和響應，轉發和重定向，我覺得差不多夠用了。當然，要是細究的話也不止這些，我針對的是新手。
轉發與重定向簡介
轉發和重定向都是實現頁面跳轉，也就是說，當我們訪問一個Servlet 的時候，Servlet幫我們跳轉到另一個界面。
轉發與重定向的區別
實現轉發調用的是HttpServletRequest對象中的方法
實現重定向調用的是HttpServletResponse對象中的方法
轉發時瀏覽器中的url地址不會發生改變
重定向時瀏覽器中的url地址會發生改變
轉發時瀏覽器只請求一次服務器
重定向時瀏覽器請求兩次服務器
轉發能使用request帶數據到跳轉的頁面
重定向能使用ServletContext帶數據到跳轉的頁面
代碼演示轉發和重定向
package servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/login")
public class ServletDemo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//獲取表單提交過來的數據
//getParameter()方法可以獲取請求的參數信息
String name = req.getParameter("name");
String password = req.getParameter("password");
//打印獲取到的參數信息
System.out.println("name:"+name);
System.out.println("password:"+password);
//如果name=admin,password=123,則跳轉到succee.jsp,否則跳轉到fail.jsp
if("admin".equals(name)&&"123".equals(password)){
//通過轉發實現跳轉
req.getRequestDispatcher("/success.jsp").forward(req,resp);
}else {
//通過重定向實現跳轉
resp.sendRedirect("/fail.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
JSP代碼
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登錄</title>
</head>
<body>
<form action="/login">
<table align="center">
<tr>
<td>賬號:</td>
<td><input type="text" name="name"></td>
</tr>
<tr>
<td>密碼:</td>
<td><input type="text" name="password"></td>
</tr>
<tr>
<td><input type="submit" value="登錄"></td>
<td><input type="reset" value="重置"></td>
</tr>
</table>
</form>
</body>
</html>
轉發和重定向如何帶數據到某個頁面
package servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/login")
public class ServletDemo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//通過轉發帶數據
req.setAttribute("name","張三");
req.getRequestDispatcher("/send.jsp").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
send.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>轉發和重定向傳代數據練習</title>
</head>
<body>
<%
//1、接收轉發傳代的數據
String name = (String) request.getAttribute("name");
out.println("轉發傳代的數據："+name);
%>
</body>
</html>
package servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/login")
public class ServletDemo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//通過重定向帶數據
ServletContext servletContext = this.getServletContext();
servletContext.setAttribute("name","王二麻子");
resp.sendRedirect("/send2.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
send2.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>轉發和重定向傳代數據練習</title>
</head>
<body>
<%
//1、接收重定向傳代的數據
String name1 = (String)application.getAttribute("name");
out.println("重定向傳代的數據："+name1);
%>
</body>
</html>
練習
index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="CountServlet" method="post">
<h3>加法計算器</h3>
加數1：<input type="number" name="one">
加數2：<input type="number" name="two">
<input type="submit" value="計算">
</form>
</body>
</html>
count.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
計算結果：<%=request.getAttribute("count")%>
<!--計算結果：<%=application.getAttribute("count")%>-->
</body>
</html>
Servlet
package servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/CountServlet")
public class CountServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String one=request.getParameter("one");
int o=Integer.parseInt(one);//強制轉換，將String類型的數據轉換成int類型
String two=request.getParameter("two");
int t=Integer.parseInt(two);//強制轉換，將String類型的數據轉換成int類型
System.out.println(one+" "+two);
int c=o+t;
String co=String.valueOf(c);//將int類型的數據轉換成String類型
//轉發，可以攜帶數據
request.setAttribute("count",co);
request.getRequestDispatcher("count.jsp").forward(request,response);
//用於存放數據
// ServletContext s=this.getServletContext();
// s.setAttribute("count",co);
//重定向只能依靠ServletContext獲取數據
// response.sendRedirect("count.jsp");
System.out.println(co);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
結束語
Servlet分享到此結束，想了解更多的朋友可以看之前總結過的博客《Servlet》,和《JSP》 ,更多精彩等你來學習。
*****************************************************************************************************
我的博客園地址：https://www.cnblogs.com/zyx110/
本文已獨家授權給腳本之家(jb51net)公眾號獨家發布