servlet redirect/forward/session/cookie 与 HTTP 协议的测试

 本文直接展示servlet的测试结果。

servlet的代码中使用sendRedirect：

public class SessionTest extends HttpServlet {
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
...
response.sendRedirect("http://localhost:8080/web/");
...}

查看浏览器交互过程，先是请求该servlet：

1. Request URL:
   http://localhost:8080/web/SessionTest
2. Request Method:
   GET
3. Status Code:
   
   302 Found
4. Request Headersview source
1. Accept:
   text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
2. Accept-Encoding:
   gzip,deflate,sdch
3. Accept-Language:
   en-US,en;q=0.8,zh;q=0.6,ko;q=0.4,ja;q=0.2
4. Cache-Control:
   max-age=0
5. Connection:
   keep-alive
6. Host:
   localhost:8080
7. User-Agent:
   Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36
5. Response Headersview source
1. Content-Length:
   0
2. Content-Type:
   text/html;charset=UTF-8
3. Date:
   Thu, 06 Jun 2013 07:16:55 GMT
4. Location:
   http://localhost:8080/web/
5. Server:
   Apache-Coyote/1.1
6. Set-Cookie:
   JSESSIONID=8C8DCD7355CC62C75C9BD154B2ADEDD0; Path=/web/; HttpOnly

可以看到response返回了302，并带上了location, 指示浏览器做第二次跳转请求，浏览器得到提示后进行第二次请求。

同样的servlet，将代码改为forward，实现了在servlet容器内部的跳转，对浏览器实际上是不可见得。

request.getRequestDispatcher("/index.jsp").forward(request, response);

看一下tomcat服务器的响应，一个200  OK之后，直接返回了内容，很直接

1. Request URL:
   http://localhost:8080/web/SessionTest
2. Request Method:
   GET
3. Status Code:
   
   200 OK
4. Request Headersview source
1. Accept:
   text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
2. Accept-Encoding:
   gzip,deflate,sdch
3. Accept-Language:
   en-US,en;q=0.8,zh;q=0.6,ko;q=0.4,ja;q=0.2
4. Connection:
   keep-alive
5. Cookie:
   JSESSIONID=4D4C34D45462707E53A475C060E2D2A2; test=test
6. DNT:
   1
7. Host:
   localhost:8080
8. User-Agent:
   Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36
5. Response Headersview source
1. Content-Length:
   218
2. Content-Type:
   text/html;charset=UTF-8
3. Date:
   Thu, 06 Jun 2013 09:12:04 GMT
4. Server:
   Apache-Coyote/1.1
5. Set-Cookie:
   JSESSIONID=0FE64A4D2D1777BD44F08F2F8186384B; Path=/web/; HttpOnly

再看cookie的保存，将以上代码改为将cookie加入response：

        Cookie cookie = new Cookie("test","test");
        response.addCookie(cookie);
        PrintWriter out = response.getWriter();

再看HTTP head：

1. Request URL:
   http://localhost:8080/web/SessionTest
2. Request Method:
   GET
3. Status Code:
   
   200 OK
4. Request Headersview source
1. Accept:
   text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
2. Accept-Encoding:
   gzip,deflate,sdch
3. Accept-Language:
   en-US,en;q=0.8,zh;q=0.6,ko;q=0.4,ja;q=0.2
4. Cache-Control:
   max-age=0
5. Connection:
   keep-alive
6. Cookie:
   JSESSIONID=FB43328EF48C78B7122454F84B57F164
7. DNT:
   1
8. Host:
   localhost:8080
9. User-Agent:
   Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36
5. Response Headersview source
1. Content-Length:
   186
2. Content-Type:
   text/html;charset=UTF-8
3. Date:
   Thu, 06 Jun 2013 07:47:13 GMT
4. Server:
   Apache-Coyote/1.1
5. Set-Cookie:
   JSESSIONID=BC3FDA2D942F2F4B50757D9C436D21A9; Path=/web/; HttpOnly
6. Set-Cookie:
   test=test

Tomcat通过HTTP协议的Set-Cookie将servlet的cookie放入了响应头，查看浏览器的cookie，除了jsessionid，又加了一个test/test的cookie进来。