We sent a message via the HTTP gateway listener and received a synchronous response, on the same connection which transferred the request.

Here is the listing of the client code for reference:

public static void main(String[] args) throws Exception {
    String serverURL = "http://localhost:8080/Chapter6/http/Chapter6Sample/Chapter6Service";
    HttpURLConnection connection = (HttpURLConnection)new URL(serverURL).openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.connect();
    PrintWriter out = new PrintWriter(new OutputStreamWriter(connection.getOutputStream()));
    out.println("Hello Http Gateway!");
    out.close();
    BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
    String inputLine;
    while ((inputLine = in.readLine()) != null) {
        System.out.println(inputLine);
    }
    in.close();
}

Go ahead and modify the listener to add asynchronous behavior. Are you able to send a GET request now? What status code does it return by default?

Aspects of the HTTP configuration can be shared between multiple gateways, specified through the <http-provider> or <http-bus> elements.

The <http-provider> element exposes the shared configuration of the HTTP exception mappings. Using the <exception> element specifies the translations from exceptions into the appropriate HTTP response.

The <http-bus> element exposes the shared configuration of the HTTP methods that are supported using the <protected-methods> element, the security roles required to access the endpoint using the <allowed-roles> element, and any requirement to secure the HTTP transport using the transportGuarantee attribute.

A typical HTTP provider configuration would look like this:

<http-provider name="http">
  <http-bus busid="chapter6HttpGateway"
            transportGuarantee="CONFIDENTIAL">
    <allowed-roles>
      <role name="friend">
    </allowed-roles>
    <protected-methods>
      <method name="GET">
      <method name="PUT">
      <method name="POST">
      <method name="DELETE">
    </protected-methods>
  </http-bus>
  <exception mappingsFile="/http-exception-mappings.properties"/>
</http-provider>

Note that the configuration stipulates a requirement to use a CONFIDENTIAL transport, in other words SSL, and requires the user to authenticate using credentials that include the friend role.

The exception element can also be configured directly as shown in the following:

<exception>
  <mapping class="com.acme.AcmeException" status="503"/>
</exception>

Go ahead and secure the http-provider in our sample. Try using exception mapping with HTTP status codes both globally in the http-provider and also in http-gateway.