Java 如何将 http 请求发送到另一个 servlet

How can I send http request to another servlet

提问by Hanumath

In my project folder,We have 2 java files under ContextPath/WEB-INF/Classes/*.classnames are App1.classand App2.class

在我的项目文件夹中，ContextPath/WEB-INF/Classes/*.class名称下有 2 个 java 文件App1.class和App2.class

If I want to Run App1.class,Just i need to trigger URL in browser.

如果我想运行App1.class，只需要在浏览器中触发 URL。

  http://localhost:8080/Mapping/App1

in the same way,if you want to trigger App2.class,use the following link

同样的，如果你想触发App2.class，使用以下链接

 http://localhost:8080/Mapping/App2

I want to trigger App2from App1,means If you trigger App1with corresponding URL in browser,It will be trigger App2.

我想触发App2从App1如果触发，方式App1与在浏览器对应的URL，这将是触发App2。

I don't want to any response also.

我也不想要任何回应。

How can I do this.

我怎样才能做到这一点。

can anyone help me.

谁能帮我。

Thanks.

谢谢。

回答by Robadob

You could send a Get request using Java;

您可以使用 Java 发送 Get 请求；

URL url = new URL("http://localhost:8080/Mapping/App2");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setRequestMethod("GET");
conn.connect();

Alternatively you should probably configure App2 so that it's action is handled by a separate class or a method accessible to both servlets.

或者，您可能应该配置 App2，以便它的操作由单独的类或两个 servlet 均可访问的方法处理。

回答by Ravi Thapliyal

I want to trigger App2 from App1,means If you trigger App1 with corresponding URL in browser,It will be trigger App2.

我想从App1触发App2，意思是如果你在浏览器中用对应的URL触发App1，它会触发App2。

Considering App1and App2are configured as servlets in your Mappingweb-app; you can make use of a RequestDispatcherto forward()the request to App2. This would happen server-side i.e. the browser would receive the response as if its coming from App1.

考虑App1并App2在您的Mappingweb 应用程序中配置为 servlet ；您可以使用 aRequestDispatcher来forward()请求App2。这将发生在服务器端，即浏览器会收到响应，就好像它来自App1.

if (isForwardReqd()) {
    RequestDispatcher rd = request.getRequestDispatcher("App2");
    rd.forward(request, response);
}

Please, note App1must not have committed a response before doing the forward(), otherwise you'd get an IllegalStateException.

请注意，App1在执行 之前一定不要提交响应forward()，否则您会得到IllegalStateException.

Reference:
http://docs.oracle.com/javaee/7/api/javax/servlet/RequestDispatcher.html

参考：http :
//docs.oracle.com/javaee/7/api/javax/servlet/RequestDispatcher.html

Defines an object that receives requests from the client and sends them to any resource (such as a servlet, HTML file, or JSP file) on the server.

定义一个对象，该对象接收来自客户端的请求并将它们发送到服务器上的任何资源（例如 servlet、HTML 文件或 JSP 文件）。

回答by Yash

Possible Ways

可能的方法

HTTP GETrequest with (optionally) query parameters

带有（可选）查询参数的HTTP GET请求

String query = String.format("param1=%s&param2=%s", 
             URLEncoder.encode("param1Value", "UTF-8"), 
             URLEncoder.encode("param1Value", "UTF-8"));

    URL url = new URL(servletURL + "?" + query);
    HttpURLConnection conn = (HttpURLConnection)url.openConnection();
    conn.setRequestMethod("GET");
    Map<String, List<String>> header = conn.getHeaderFields();
    int responseCode = conn.getResponseCode();
    System.out.println("Headers : "+header);
    System.out.println("Response Code "+responseCode);

RequestDispatcher- Dispatch the Request from one resource to other-resource. If they are available in same project & server.

RequestDispatcher- 将请求从一个资源分派到另一个资源。如果它们在同一项目和服务器中可用。

• This interface allows you to do a server side forward/include, executes service(...)/doGet(...) method of requested Servlet.

  RequestDispatcher rd = req.getRequestDispatcher("/servlet2");
  rd.forward(req, resp); // rd.include(req, resp);
  

  Same Server, Different-Project

  RequestDispatcher rd = req.getServletContext().getContext("/Project2").getRequestDispatcher("/ips");
      rd.forward(req,  resp);
  

• 该接口允许您执行服务器端转发/包含，执行请求的 Servlet 的 service(...)/doGet(...) 方法。

  RequestDispatcher rd = req.getRequestDispatcher("/servlet2");
  rd.forward(req, resp); // rd.include(req, resp);
  

  相同的服务器，不同的项目

  RequestDispatcher rd = req.getServletContext().getContext("/Project2").getRequestDispatcher("/ips");
      rd.forward(req,  resp);
  

.sendRedirect()

.sendRedirect()

• Redirects the request from client side[URL get changed in client's browser].
• When server encounters sendRedirect method it Sends a temporary redirect response to the client with 3XX status code, then requests new URL.

• www.sun.com redirects to www.oracle.com/sun/index.html

  response.sendRedirect(servletURL); // Different Server.
  

• 重定向来自客户端的请求 [URL 在客户端浏览器中更改]。
• 当服务器遇到 sendRedirect 方法时，它会向客户端发送一个带有 3XX 状态码的临时重定向响应，然后请求新的 URL。

• www.sun.com 重定向到 www.oracle.com/sun/index.html

  response.sendRedirect(servletURL); // Different Server.
  

Invoking Other Servletusing different ways

Invoking Other Servlet使用不同的方式