Use server.port=0 for scanning

This leverages existing capabilities of teh JDK and the OS
to grab a port at random and not have it stolen by another
process. It's very hard to avoid that race condition in
pure Java code, so why bother?

User can set port<0 to disable autoStart of connectors (e.g.
to start a web application context but not have it listen on
any port). In that case the actual socket port will be set to
0 (and therefore if it ever starts up the local port will
be random).

spring-boot/src/main/java/org/springframework/boot/context/embedded/AbstractEmbeddedServletContainerFactory.java

@@ -82,7 +82,6 @@ public abstract class AbstractEmbeddedServletContainerFactory implements
 	 * @param port the port number for the embedded servlet container
 	 */
 	public AbstractEmbeddedServletContainerFactory(int port) {
-		checkPort(port);
 		this.port = port;
 	}
 
@@ -94,7 +93,6 @@ public abstract class AbstractEmbeddedServletContainerFactory implements
 	 */
 	public AbstractEmbeddedServletContainerFactory(String contextPath, int port) {
 		checkContextPath(contextPath);
-		checkPort(port);
 		this.contextPath = contextPath;
 		this.port = port;
 	}
@@ -129,16 +127,9 @@ public abstract class AbstractEmbeddedServletContainerFactory implements
 
 	@Override
 	public void setPort(int port) {
-		checkPort(port);
 		this.port = port;
 	}
 
-	private void checkPort(int port) {
-		if (port < 0 || port > 65535) {
-			throw new IllegalArgumentException("Port must be between 1 and 65535");
-		}
-	}
-
 	/**
 	 * Returns the port that the embedded servlet container should listen on.
 	 */

spring-boot/src/main/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainer.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.context.embedded.jetty;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.eclipse.jetty.server.Connector;
 import org.eclipse.jetty.server.Server;
 import org.springframework.boot.context.embedded.EmbeddedServletContainer;
@@ -28,10 +30,13 @@ import org.springframework.util.Assert;
  * {@link JettyEmbeddedServletContainerFactory} and not directly.
  * 
  * @author Phillip Webb
+ * @author Dave Syer
  * @see JettyEmbeddedServletContainerFactory
  */
 public class JettyEmbeddedServletContainer implements EmbeddedServletContainer {
 
+	private final Log logger = LogFactory.getLog(JettyEmbeddedServletContainer.class);
+
 	private final Server server;
 	private boolean autoStart;
 
@@ -81,6 +86,7 @@ public class JettyEmbeddedServletContainer implements EmbeddedServletContainer {
 			Connector[] connectors = this.server.getConnectors();
 			for (Connector connector : connectors) {
 				connector.start();
+				this.logger.info("Jetty started on port: " + connector.getLocalPort());
 			}
 		}
 		catch (Exception ex) {

spring-boot/src/main/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainerFactory.java

@@ -97,7 +97,8 @@ public class JettyEmbeddedServletContainerFactory extends
 	public EmbeddedServletContainer getEmbeddedServletContainer(
 			ServletContextInitializer... initializers) {
 		WebAppContext context = new WebAppContext();
-		Server server = new Server(new InetSocketAddress(getAddress(), getPort()));
+		int port = getPort() >= 0 ? getPort() : 0;
+		Server server = new Server(new InetSocketAddress(getAddress(), port));
 
 		if (this.resourceLoader != null) {
 			context.setClassLoader(this.resourceLoader.getClassLoader());
@@ -123,7 +124,7 @@ public class JettyEmbeddedServletContainerFactory extends
 		postProcessWebAppContext(context);
 
 		server.setHandler(context);
-		this.logger.info("Server initialized with port: " + getPort());
+		this.logger.info("Server initialized with port: " + port);
 		return getJettyEmbeddedServletContainer(server);
 	}
 
@@ -241,7 +242,7 @@ public class JettyEmbeddedServletContainerFactory extends
 	 * @return a new {@link JettyEmbeddedServletContainer} instance
 	 */
 	protected JettyEmbeddedServletContainer getJettyEmbeddedServletContainer(Server server) {
-		return new JettyEmbeddedServletContainer(server, getPort() > 0);
+		return new JettyEmbeddedServletContainer(server, getPort() >= 0);
 	}
 
 	@Override

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainer.java

@@ -104,6 +104,7 @@ public class TomcatEmbeddedServletContainer implements EmbeddedServletContainer
 		if (connector != null && this.autoStart) {
 			try {
 				connector.getProtocolHandler().start();
+				this.logger.info("Tomcat started on port: " + connector.getLocalPort());
 			}
 			catch (Exception ex) {
 				this.logger.error("Cannot start connector: ", ex);

spring-boot/src/main/java/org/springframework/boot/context/embedded/tomcat/TomcatEmbeddedServletContainerFactory.java

@@ -193,12 +193,8 @@ public class TomcatEmbeddedServletContainerFactory extends
 
 	// Needs to be protected so it can be used by subclasses
 	protected void customizeConnector(Connector connector) {
-		if (getPort() > 0) {
-			connector.setPort(getPort());
-		}
-		else {
-			connector.setPort(8080);
-		}
+		int port = getPort() >= 0 ? getPort() : 0;
+		connector.setPort(port);
 		if (connector.getProtocolHandler() instanceof AbstractProtocol) {
 			if (getAddress() != null) {
 				((AbstractProtocol) connector.getProtocolHandler())
@@ -259,7 +255,7 @@ public class TomcatEmbeddedServletContainerFactory extends
 	 */
 	protected TomcatEmbeddedServletContainer getTomcatEmbeddedServletContainer(
 			Tomcat tomcat) {
-		return new TomcatEmbeddedServletContainer(tomcat, getPort() > 0);
+		return new TomcatEmbeddedServletContainer(tomcat, getPort() >= 0);
 	}
 
 	private File createTempDir(String prefix) {