Added check for invalid hostname

The exception class has to be "fixed"

You may register a serviceId with invalid URI characters (e.g.: '_'), but the URI::getHost() fails when such chars are found.

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/ribbon/RibbonClientHttpRequestFactory.java

@@ -48,6 +48,9 @@ public class RibbonClientHttpRequestFactory implements ClientHttpRequestFactory
 	public ClientHttpRequest createRequest(URI originalUri, HttpMethod httpMethod)
 			throws IOException {
         String serviceId = originalUri.getHost();
+        if (serviceId == null) {
+            throw new IOException("Invalid hostname in the URI [" + originalUri.toASCIIString() + "]");
+        }
         ServiceInstance instance = loadBalancer.choose(serviceId);
 		if (instance == null) {
 			throw new IllegalStateException("No instances available for "+serviceId);

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/ribbon/RibbonClientHttpRequestFactoryTests.java

@@ -16,14 +16,11 @@
 
 package org.springframework.cloud.netflix.ribbon;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
 import java.net.URI;
 
-import lombok.SneakyThrows;
-
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
@@ -44,11 +41,17 @@ import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RequestParam;
 import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.client.ResourceAccessException;
 import org.springframework.web.client.RestTemplate;
 
 import com.netflix.loadbalancer.Server;
 import com.netflix.loadbalancer.ServerList;
 
+import lombok.SneakyThrows;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
 /**
  * @author Spencer Gibb
  */
@@ -59,6 +62,9 @@ import com.netflix.loadbalancer.ServerList;
 @DirtiesContext
 public class RibbonClientHttpRequestFactoryTests {
 
+	@Rule
+	public final ExpectedException exceptionRule = ExpectedException.none();
+
 	@Autowired
 	private RestTemplate restTemplate;
 
@@ -123,6 +129,13 @@ public class RibbonClientHttpRequestFactoryTests {
 		assertEquals("wrong response body", "hello world", response.getBody());
 	}
 
+	@Test
+	public void invalidHostNameError() {
+		exceptionRule.expect(ResourceAccessException.class);
+		exceptionRule.expectMessage("Invalid hostname");
+		restTemplate.getForEntity("http://simple_bad", String.class);
+	}
+
 	@Configuration
 	@EnableAutoConfiguration
 	@RestController