使用servlet和“setHeader”重定向请求方法不起作用 [英] Redirecting a request using servlets and the "setHeader" method not working
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问题描述
我是servlet开发的新手，并且正在阅读电子书，并发现可以使用
<$ c重定向到其他网页$ c> setHeader（Location，http://www.google.com）
但是，这是行不通的，因为我已经写了这段代码：
import java.io. *;
import javax.servlet。*;
import javax.servlet.http。*;
public class ModHelloWorld extends HttpServlet {$ b $ public void doGet（HttpServletRequest request，HttpServletResponse response）throws IOException {
// response.addHeader（Location，http：// www.google.com）;
response.setHeader（Location，http://www.google.com）;
response.setContentType（text / html）;
PrintWriter pw = response.getWriter（）;
pw.println（< html>< head>< title>修改后的Hello World< / title>< / head>< body>）;
pw.println（< h1>）;
// getInitParameter函数读取init-param元素的内容。
pw.println（getInitParameter（message））;
pw.println（< / h1>）;
pw.println（< / body>< / html>）;
pw.close（）;
}
}
我使用我的程序检查了标题，
import java.net。*;
import java.io. *;
class getHeaders {
public static void main（String args []）{
URL url = null;
URLConnection urc = null;
尝试{
url = new URL（args [0]）;
urc = url.openConnection（）;
for（int i = 0;; i ++）{
String name = urc.getHeaderFieldKey（i）;
字符串值= urc.getHeaderField（i）;
if（name == null&& value == null）//两个null如此结尾的头部
break;
else if（name == null）{//标题的第一行{
System.out.println（Server HTTP version，Response code：）;
System.out.println（value）;
System.out.println（第一个标题字段的ENd）;
} else {
System.out.println（header的名称是：+ name +，其值是：+ value）;
}
}
} catch（MalformedURLException e）{
System.out.println（格式错误的URL+ e.getMessage（））;
} catch（IOException e）{
e.printStackTrace（）;
}
}
}
as：
服务器HTTP版本，响应代码：
HTTP / 1.1 200 OK
第一个标头的ENd字段
header的名称是：Server和它的值是：Apache-Coyote / 1.1
header的名称是：位置和它的值是：http://www.google.com
名称的头是：Content-Type，它的值是：text / html
头的名字是：Content-Length，它的值是：101
头的名字是：Date和它的值是：Sat， 05三月2011 15:27:29 GMT
但我没有从浏览器重定向到Google的页面。
在此先感谢：）
正如你所看到的，响应仍然是 HTTP / 1.1 200 OK 。要指示重定向，您需要发回302状态码： response.setStatus（HttpServletResponse.SC_FOUND）; // SC_FOUND = 302
I am new to servlet development, and I was reading an ebook, and found that I can redirect to a different web page using
setHeader("Location", "http://www.google.com")
But this is not working, as I have written this code as:
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class ModHelloWorld extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{
// response.addHeader("Location", "http://www.google.com");
response.setHeader("Location", "http://www.google.com");
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
pw.println("<html><head><title>Modified Hello World</title></head><body>");
pw.println("<h1>");
//getInitParameter function reads the contents ot init-param elements.
pw.println(getInitParameter("message"));
pw.println("</h1>");
pw.println("</body></html>");
pw.close();
}
}
i have checked the headers using my program to get the headers of the webpage which is as under:
import java.net.*;
import java.io.*;
class getHeaders{
public static void main(String args[]){
URL url = null;
URLConnection urc = null;
try {
url = new URL(args[0]);
urc = url.openConnection();
for(int i=0 ; ; i++) {
String name = urc.getHeaderFieldKey(i);
String value = urc.getHeaderField(i);
if(name == null && value == null)//both null so end of header
break;
else if(name == null){//first line of header{
System.out.println("Server HTTP version, Response code: ");
System.out.println(value);
System.out.println("ENd of first header field");
} else {
System.out.println("name of header is: " + name + " and its value is : " + value);
}
}
} catch(MalformedURLException e){
System.out.println("Malformed URL " + e.getMessage());
} catch(IOException e){
e.printStackTrace();
}
}
}
And i am getting the output as:
Server HTTP version, Response code:
HTTP/1.1 200 OK
ENd of first header field
name of header is: Server and its value is : Apache-Coyote/1.1
name of header is: Location and its value is : http://www.google.com
name of header is: Content-Type and its value is : text/html
name of header is: Content-Length and its value is : 101
name of header is: Date and its value is : Sat, 05 Mar 2011 15:27:29 GMT
But I was not redirected to google's page from my browser.
Thanks in advance:)
解决方案
As you can see, the response is still HTTP/1.1 200 OK. To indicate a redirect, you need to send back a 302 status code:
response.setStatus(HttpServletResponse.SC_FOUND); // SC_FOUND = 302
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