如何将响应从另一个 Servlet 发送回 Servlet

Question

我编写了两个驻留在不同 Web 服务器上的 servlet。使用 java 中的 URL 对象从 Servlet1(Server1) 发送请求。并成功调用 Servlet2(server2)。但我还需要将响应从 Servlet2 发送回 Servlet1 ......我怎样才能做到这一点。请帮帮我。

更新

这是测试的代码......

Servlet1：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("Inside MyServlet.");
    String urlParameters = "param1=a&param2=b&param3=c";
    byte[] postData       = urlParameters.getBytes( StandardCharsets.UTF_8 );
    int    postDataLength = postData.length;
    String requestURL = "http://localhost:8080/Application2/Servlet2";
    URL url = new URL( requestURL );
    HttpURLConnection conn= (HttpURLConnection) url.openConnection();
    conn.setDoOutput( true );
    conn.setInstanceFollowRedirects( false );
    conn.setRequestMethod( "POST" );
    conn.setRequestProperty( "Content-Type","application/x-www-form-urlencoded");
    conn.setRequestProperty( "charset", "UTF-8");
    conn.setRequestProperty( "Content-Length", Integer.toString( postDataLength ));
    conn.setUseCaches( false );
    ObjectOutputStream out = new ObjectOutputStream(conn.getOutputStream());
    out.write( postData );
    conn.connect();
 }

Servlet2：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    System.out.println("Inside CallToAuthorize.Getting Access Token.");
    //do something here and send the response back to Servlet1.
    //Primarily i will be sending String back to Servlet1 for its request.
 }

Answer 1

您的 Servlet2，即请求接收器，应该正常运行：

• 获取请求参数
• 和他们一起做点什么
• 生成响应
• 发回

一个基本的例子：

public class Servlet2 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/plain; charset=UTF-8");
        response.getWriter().append("That is my response");
    }

}

您的客户，即请求发送者，应处理响应：

int responseCode = connection.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) {
    System.out.println("SUCCESS");
}
else {
    System.out.println("Response Code: " +  responseCode);
}

// may be get the headers
Map<String, List<String>> headers = connection.getHeaderFields();
// do something with them

// read the response body (text, html, json,..)
// do something usefull
BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
String line;

while ((line = reader.readLine()) != null) {
    System.out.println(line);
}