Added method to check subscribers

Gemfile

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in stomp.gemspec
+gemspec

lib/stomp/client.rb

@@ -281,6 +281,20 @@ def closed?()
       @connection.closed?()
     end
 
+    ##  Checks if subscriber with destination is passed is present or not
+    #   @returns [Boolean]
+    #
+    #   example
+    #     Stomp::Client.new().subscriber?('/topic/topicName')                                     => false
+    #     Stomp::Client.new().subscriber?('/queue/queueName')                                     => true
+    #     Stomp::Client.new().subscriber?('/queue/Consumer.subscriber1.VirtualTopic.topicName')   => true
+    #
+    def subscribed?(destination, headers = {})
+      headers = headers.symbolize_keys
+      headers = headers.merge(:id => build_subscription_id(destination, headers))
+      !@listeners[headers[:id]].nil?
+    end
+
     # jruby? tests if the connection has detcted a JRuby environment
     def jruby?()
       @connection.jruby

lib/stomp/connection.rb

@@ -371,6 +371,13 @@ def subscribe(destination, headers = {}, subId = nil)
       transmit(Stomp::CMD_SUBSCRIBE, headers)
     end
 
+    def subscribed?(destination, subId = nil)
+      return false unless @reliable
+
+      subId = destination if subId.nil?
+      !@subscriptions[subId].nil?
+    end
+
     # Unsubscribe from a destination.   A subscription name is required.
     # For Stomp 1.1+ a session unique subscription ID is also required.
     def unsubscribe(destination, headers = {}, subId = nil)

spec/client_spec.rb

@@ -3,7 +3,6 @@
 require 'spec_helper'
 require 'client_shared_examples'
 
-
 describe Stomp::Client do
   let(:null_logger) { double("mock Stomp::NullLogger") }
 
@@ -192,7 +191,7 @@
     it_should_behave_like "standard Client"
 
   end
-  
+
   describe "(created with authenticating stomp:// URL and non-TLD host)" do
 
     before(:each) do
@@ -283,7 +282,7 @@
     it_should_behave_like "standard Client"
 
   end
-  
+
   describe "(created with failover URL)" do
     before(:each) do
 	  @client = Stomp::Client.new('failover://(stomp://login1:passcode1@localhost:61616,stomp://login2:passcode2@remotehost:61617)')
@@ -312,63 +311,63 @@
 	  client = Stomp::Client.new(url)
       expect(client.parameters).to eq(@parameters)
     end
-    
+
     it "should properly parse a URL with failover:" do
       url = "failover:(stomp://login1:passcode1@localhost:61616,stomp://login2:passcode2@remotehost1:61617,stomp://login3:passcode3@remotehost2:61618)"
-      
+
       @parameters[:hosts] = [
         {:login => "login1", :passcode => "passcode1", :host => "localhost", :port => 61616, :ssl => false},
         {:login => "login2", :passcode => "passcode2", :host => "remotehost1", :port => 61617, :ssl => false},
         {:login => "login3", :passcode => "passcode3", :host => "remotehost2", :port => 61618, :ssl => false}
       ]
-      
+
       @parameters.merge!({:logger => null_logger})
 	  @parameters[:client_main] = @cli_thread
       expect(Stomp::Connection).to receive(:new).with(@parameters)
       client = Stomp::Client.new(url)
       expect(client.parameters).to eq(@parameters)
     end
-    
+
     it "should properly parse a URL without user and password" do
       url = "failover:(stomp://localhost:61616,stomp://remotehost:61617)"
 
       @parameters[:hosts] = [
         {:login => "", :passcode => "", :host => "localhost", :port => 61616, :ssl => false},
         {:login => "", :passcode => "", :host => "remotehost", :port => 61617, :ssl => false}
       ]
-      
+
       @parameters.merge!({:logger => null_logger})
       @parameters[:client_main] = @cli_thread
       expect(Stomp::Connection).to receive(:new).with(@parameters)
-      
+
       client = Stomp::Client.new(url)
 	  @parameters[:client_main] = client.parameters[:client_main]
       expect(client.parameters).to eq(@parameters)
     end
-    
+
     it "should properly parse a URL with user and/or password blank" do
       url = "failover:(stomp://@localhost:61616,stomp://@remotehost:61617)"
-      
+
       @parameters[:hosts] = [
         {:login => "", :passcode => "", :host => "localhost", :port => 61616, :ssl => false},
         {:login => "", :passcode => "", :host => "remotehost", :port => 61617, :ssl => false}
       ]
-      
+
       @parameters.merge!({:logger => null_logger})
       @parameters[:client_main] = @cli_thread
       expect(Stomp::Connection).to receive(:new).with(@parameters)
-      
+
       client = Stomp::Client.new(url)
 	  @parameters[:client_main] = client.parameters[:client_main]
       expect(client.parameters).to eq(@parameters)
     end
-    
+
     it "should properly parse a URL with the options query" do
       query = "initialReconnectDelay=5000&maxReconnectDelay=60000&useExponentialBackOff=false&backOffMultiplier=3"
       query += "&maxReconnectAttempts=4&randomize=true&backup=true&timeout=10000"
-      
+
       url = "failover:(stomp://login1:passcode1@localhost:61616,stomp://login2:passcode2@remotehost:61617)?#{query}"
-      
+
       #
       @parameters = {
         :initial_reconnect_delay => 5.0,
@@ -380,21 +379,21 @@
         :connect_timeout => 0,
         :reliable => true
       }
-      
+
       @parameters[:hosts] = [
         {:login => "login1", :passcode => "passcode1", :host => "localhost", :port => 61616, :ssl => false},
         {:login => "login2", :passcode => "passcode2", :host => "remotehost", :port => 61617, :ssl => false}
       ]
-      
+
       @parameters.merge!({:logger => null_logger})
       @parameters[:client_main] = @cli_thread
       expect(Stomp::Connection).to receive(:new).with(@parameters)
-      
+
       client = Stomp::Client.new(url)
 	  @parameters[:client_main] = client.parameters[:client_main]
       expect(client.parameters).to eq(@parameters)
     end
-    
+
   end
 
 
@@ -407,7 +406,7 @@
         message.command = Stomp::CMD_ERROR
         message
       end
-  
+
       it 'should handle ProducerFlowControlException errors by raising' do
         expect do
           @client = Stomp::Client.new
@@ -472,6 +471,27 @@ def original_headers
       it_behaves_like 'argument-safe method'
     end
 
+    describe '#subscribed?' do
+      subject { @client.subscribed?('/topic/topicName') }
+
+      context 'When subscription is present' do
+        before {
+          allow(@mock_connection).to receive(:subscribe)
+          @client.subscribe('/topic/topicName') { |message| }
+        }
+
+        it 'returns true' do
+          expect(subject).to be true
+        end
+      end
+
+      context 'When subscription is not present' do
+        it 'returns false' do
+          expect(subject).to be false
+        end
+      end
+    end
+
     describe '#unsubscribe' do
       let(:connection_headers) { original_headers.merge({:id => Digest::SHA1.hexdigest('destination')}) }
       before {
@@ -563,6 +583,5 @@ def original_headers
         it_behaves_like 'argument-safe method'
       end
     end
-
   end
 end