find unused port, write port info to a file

Author: mmhelloworld

jvm-assembler-server/pom.xml

@@ -10,24 +10,6 @@
     <modelVersion>4.0.0</modelVersion>
 
     <artifactId>jvm-assembler-server</artifactId>
-    <packaging>war</packaging>
-
-    <build>
-        <plugins>
-            <plugin>
-                <groupId>org.eclipse.jetty</groupId>
-                <artifactId>jetty-maven-plugin</artifactId>
-            </plugin>
-
-            <plugin>
-                <artifactId>maven-war-plugin</artifactId>
-                <configuration>
-                    <warName>jvm-assembler-core</warName>
-                    <failOnMissingWebXml>false</failOnMissingWebXml>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
 
     <dependencies>
 

jvm-assembler-server/src/main/java/com/mmhelloworld/jvmassembler/server/AssemblerApp.java

@@ -0,0 +1,17 @@
+package com.mmhelloworld.jvmassembler.server;
+
+import javax.ws.rs.core.Application;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * User: marimuthu
+ */
+public class AssemblerApp extends Application {
+    @Override
+    public Set<Class<?>> getClasses() {
+        Set<Class<?>> resources = new HashSet<>();
+        resources.add(AssemblerResource.class);
+        return resources;
+    }
+}

jvm-assembler-server/src/main/java/com/mmhelloworld/jvmassembler/server/AssemblerServer.java

@@ -1,35 +1,101 @@
 package com.mmhelloworld.jvmassembler.server;
 
 import org.eclipse.jetty.server.Server;
+import org.eclipse.jetty.server.ServerConnector;
 import org.eclipse.jetty.servlet.ServletContextHandler;
 import org.eclipse.jetty.servlet.ServletHolder;
+import org.glassfish.jersey.servlet.ServletContainer;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.Scanner;
 
-/**
- *
- */
 public class AssemblerServer {
     public static void main(String[] args) throws Exception {
+        int alreadyRunningPort = readPort();
+        if (alreadyRunningPort >= 0) {
+            System.err.printf("A server may be already running on port %d.\n", alreadyRunningPort);
+            System.out.println("Do you want to force start a new server? (y/n)");
+            final Scanner in = new Scanner(System.in);
+            if (in.hasNext() && !in.nextLine().equalsIgnoreCase("y")) {
+                System.exit(0);
+            }
+        }
+        startServer();
+    }
+
+    private static void startServer() throws Exception {
         ServletContextHandler context = new ServletContextHandler(ServletContextHandler.SESSIONS);
         context.setContextPath("/");
 
-        Server jettyServer = new Server(8080);
-        jettyServer.setHandler(context);
-
-        ServletHolder jerseyServlet = context.addServlet(
-                org.glassfish.jersey.servlet.ServletContainer.class, "/*");
+        ServletHolder jerseyServlet = context.addServlet(ServletContainer.class, "/*");
         jerseyServlet.setInitOrder(0);
+        jerseyServlet.setInitParameter("javax.ws.rs.Application", AssemblerApp.class.getCanonicalName());
 
-        // Tells the Jersey Servlet which REST service/class to load.
-        jerseyServlet.setInitParameter(
-                "jersey.config.server.provider.classnames",
-                AssemblerResource.class.getCanonicalName());
+        Server jettyServer = new Server(0);
+        jettyServer.setHandler(context);
 
         try {
             jettyServer.start();
+            int port = getPort(jettyServer);
+            System.out.printf("Server started successfully and is running on port %s.\n", port);
+            writePort(port);
+            Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+                getInfoFile().delete();
+            }));
             jettyServer.join();
         } finally {
             jettyServer.destroy();
         }
+    }
+
+    private static void writePort(final int port) {
+        final File portInfoFile = getInfoFile();
+        getWorkingDir().mkdir();
+        try (BufferedWriter out = new BufferedWriter(new FileWriter(portInfoFile))) {
+            out.append(Integer.toString(port));
+        } catch (IOException e) {
+            System.err.println("Cannot write port details to " + portInfoFile);
+            e.printStackTrace();
+        }
+    }
+
+    private static int readPort() throws IOException {
+        final File portInfoFile = getInfoFile();
+        if (portInfoFile.exists()) {
+            return Files.lines(portInfoFile.toPath())
+            .findFirst()
+            .map(s -> parseIntWithDefault(s, -1))
+            .orElse(-1);
+        } else {
+            return -1;
+        }
+
+    }
+
+    private static File getInfoFile() {
+        File idrisjvmWorkDir = getWorkingDir();
+        return new File(idrisjvmWorkDir, ".assembler");
+    }
+
+    private static int parseIntWithDefault(String portStr, int dflt) {
+        try {
+            return Integer.parseInt(portStr);
+        } catch (NumberFormatException e) {
+            return dflt;
+        }
+    }
 
+    private static File getWorkingDir() {
+        final String userHome = System.getProperty("user.home");
+        return new File(userHome, ".idrisjvm");
     }
+
+    private static int getPort(final Server jettyServer) {
+        return ((ServerConnector) (jettyServer.getConnectors()[0])).getLocalPort();
+    }
+
 }

pom.xml

@@ -29,16 +29,11 @@
                         <source>1.8</source>
                         <target>1.8</target>
                     </configuration>
-            </plugin>
+                </plugin>
                 <plugin>
                     <groupId>org.eclipse.jetty</groupId>
                     <artifactId>jetty-maven-plugin</artifactId>
-                    <version>9.3.11.v20160721</version>
-                </plugin>
-
-                <plugin>
-                    <artifactId>maven-war-plugin</artifactId>
-                    <version>2.6</version>
+                    <version>${jetty.version}</version>
                 </plugin>
             </plugins>
         </pluginManagement>
@@ -101,7 +96,6 @@
                 <artifactId>asm-all</artifactId>
                 <version>${asm.version}</version>
             </dependency>
-
         </dependencies>
     </dependencyManagement>