Using the HttpServlet class to set a handler

You can set a handler by overriding the selected methods of the HttpServlet class.

Cloud Functions will automatically redirect each HTTP request to your handler, depending on the HTTP method that this request was initiated with.For example, a GET request is redirected to your handler's doGet method and a POST request to the doPost method. For a successful redirect, the corresponding handler methods must exist, otherwise the function returns the HTTP method XXX is not supported by this URL message with code 405.

Unsupported methods

When using this model, please note that some methods of the HttpServletRequest and HttpServletResponse classes are not supported by Cloud Functions.

HttpServletRequest:

• getAuthType
• getCookies
• upgrade
• authenticate
• login
• logout
• getContextPath
• getServletPath
• getPathTranslated
• getRealPath
• getRemotePort
• getLocalAddr
• getLocalPort
• getServerPort
• isUserInRole
• getUserPrincipal
• getRequestedSessionId
• getSession
• changeSessionId
• isRequestedSessionIdValid
• isRequestedSessionIdFromCookie
• isRequestedSessionIdFromURL
• isRequestedSessionIdFromUrl

HttpServletResponse:

• encodeURL
• encodeRedirectURL
• encodeUrl
• encodeRedirectUrl

Example of modeling various function behaviors when invoked using different HTTP methods

The Handler.java file:

import java.io.IOException;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Handler extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
    // by setting the Content-Type to text/html, we let the browser render the HTML code
    response.setContentType("text/html");
    // displayed in bold when the function is invoked from the browser
    response.getOutputStream().print("<b>Hello, world. In bold.</b>");
  }

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
    var name = request.getParameter("name");
    response.getWriter().println("Hello, " + name);
    // the printWriter class returned by the getWriter method, make sure it's closed
    response.getWriter().close();
  }
}

Sample requests:

The GET method:

<b>Hello, world. In bold.</b>

The POST method, the name=Anonymous request parameter:

Hello, Anonymous

The PUT method:

HTTP method PUT is not supported by this URL