Add NoopDiscoveryClient and configuration

This is so that @EnableDiscoveryClient can be used (e.g. accidentally
or transitively via @EnableZuulProxy) without any actual discovery
provider on the classpath.

Fixes gh-3

src/main/java/org/springframework/cloud/client/discovery/NoopDiscoveryClient.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2013-2014 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.cloud.client.discovery;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.cloud.client.ServiceInstance;
+
+/**
+ * @author Dave Syer
+ *
+ */
+public class NoopDiscoveryClient implements DiscoveryClient {
+
+	private final ServiceInstance instance;
+	
+	public NoopDiscoveryClient(ServiceInstance instance) {
+		this.instance = instance;
+	}
+
+	@Override
+	public String description() {
+		return "Spring Cloud No-op DiscoveryClient";
+	}
+
+	@Override
+	public ServiceInstance getLocalServiceInstance() {
+		return instance;
+	}
+
+	@Override
+	public List<ServiceInstance> getInstances(String serviceId) {
+		return Collections.emptyList();
+	}
+
+	@Override
+	public List<ServiceInstance> getAllInstances() {
+		return Collections.emptyList();
+	}
+
+	@Override
+	public List<String> getServices() {
+		return Collections.emptyList();
+	}
+
+}

src/main/java/org/springframework/cloud/client/discovery/NoopDiscoveryClientConfiguration.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2013-2014 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.cloud.client.discovery;
+
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+import javax.annotation.PostConstruct;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
+import org.springframework.boot.autoconfigure.web.ServerProperties;
+import org.springframework.boot.context.embedded.EmbeddedServletContainer;
+import org.springframework.boot.context.embedded.EmbeddedWebApplicationContext;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.cloud.client.DefaultServiceInstance;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.core.env.Environment;
+
+/**
+ * @author Dave Syer
+ *
+ */
+@Configuration
+@EnableConfigurationProperties
+@ConditionalOnMissingClass(name = "com.netflix.discovery.EurekaClientConfig")
+@ConditionalOnExpression("!${eureka.client.enabled:false}")
+public class NoopDiscoveryClientConfiguration implements ApplicationListener<ContextRefreshedEvent> {
+
+	private static final Logger logger = LoggerFactory
+			.getLogger(NoopDiscoveryClientConfiguration.class);
+
+	@Autowired(required = false)
+	private ServerProperties server;
+
+	@Autowired
+	private ApplicationContext context;
+
+	@Autowired
+	private Environment environment;
+
+	private DefaultServiceInstance serviceInstance;
+
+	@PostConstruct
+	public void init() {
+		String host = "localhost";
+		try {
+			host = InetAddress.getLocalHost().getHostName();
+		}
+		catch (UnknownHostException e) {
+			logger.error("Cannot get host info", e);
+		}
+		int port = 0;
+		if (server != null && server.getPort() != null) {
+			port = server.getPort();
+		}
+		if (context instanceof EmbeddedWebApplicationContext) {
+			EmbeddedServletContainer container = ((EmbeddedWebApplicationContext) context)
+					.getEmbeddedServletContainer();
+			if (container != null) {
+				// TODO: why is it null
+				port = container.getPort();
+			}
+		}
+		serviceInstance = new DefaultServiceInstance(environment.getProperty(
+				"spring.application.name", "application"), host, port);
+	}
+	
+	@Override
+	public void onApplicationEvent(ContextRefreshedEvent event) {
+		context.publishEvent(new InstanceRegisteredEvent<Environment>(this, environment));
+	}
+
+	@Bean
+	public DiscoveryClient discoveryClient() {
+		return new NoopDiscoveryClient(serviceInstance);
+	}
+
+}

src/main/resources/META-INF/spring.factories

@@ -1,3 +1,4 @@
 # Bootstrap Configuration
 org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
-org.springframework.cloud.client.CommonsClientAutoConfiguration
+org.springframework.cloud.client.CommonsClientAutoConfiguration,\
+org.springframework.cloud.client.discovery.NoopDiscoveryClientConfiguration