Binding DeploymentManager to embedded Jetty server - jetty

Question

I'm reading the following documentation
regarding the deployment architecture of embedded Jetty, and I tried to configure a very simple jetty server that loads initially without any WebApps or handlers deployed. The server should hot deploy WARs which are copied to a static directory.
My Code:
public class JettyServerDeploymentManager implements JettyServer {
private Server server;
private DeploymentManager deployer;
private AppProvider appProvider;
public void start() throws Exception {
server = new Server(8090);
// Setup Connector
ServerConnector connector = new ServerConnector(server);
server.setConnectors(new Connector[] {connector});
// Handler Tree location for all webapps
ContextHandlerCollection contexts = new ContextHandlerCollection();
// Deployment Management
deployer = new DeploymentManager();
deployer.setContexts(contexts);
appProvider = new WebAppProvider();
((WebAppProvider) appProvider).setMonitoredDirName("/mytmpdir");
deployer.addAppProvider(appProvider);
server.addBean(deployer);
// Handler Tree
HandlerCollection handlers = new HandlerCollection();
handlers.addHandler(contexts);
handlers.addHandler(new DefaultHandler());
server.setHandler(handlers);
server.start();
server.join();
}
}
This impl should be equivalent to the code provided in the link above (xml configuration).
The server inits without any errors, but when I copy a war file to the scanned directory, nothing happens.
What am I missing? I'm not even sure if the link between my server to the deployment manager is sufficient.
Update:
It seems to be working, at least the scanning part, I've added
static
{
// Make jetty's own logging use java.util.logging
org.eclipse.jetty.util.log.Log.setLog(new JavaUtilLog());
}
And now I see in the logs that the appProvider loads a new war (it fails on NullPtr now)
Apr 08, 2019 2:51:43 PM org.eclipse.jetty.webapp.WebAppContext doStart
WARNING: Failed startup of context o.e.j.w.WebAppContext#19efba8a{/simple1,jar:file:///mytmpdir/simple1.war!/,null}{/mytmpdir/simple1.war}
java.lang.NullPointerException
at org.eclipse.jetty.webapp.MetaInfConfiguration.preConfigure(MetaInfConfiguration.java:77)
at org.eclipse.jetty.webapp.WebAppContext.preConfigure(WebAppContext.java:501)
at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:539)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:68)
at org.eclipse.jetty.deploy.bindings.StandardStarter.processBinding(StandardStarter.java:41)
at org.eclipse.jetty.deploy.AppLifeCycle.runBindings(AppLifeCycle.java:188)
at org.eclipse.jetty.deploy.DeploymentManager.requestAppGoal(DeploymentManager.java:499)
at org.eclipse.jetty.deploy.DeploymentManager.addApp(DeploymentManager.java:147)
at org.eclipse.jetty.deploy.providers.ScanningAppProvider.fileAdded(ScanningAppProvider.java:180)
at org.eclipse.jetty.deploy.providers.WebAppProvider.fileAdded(WebAppProvider.java:452)
at org.eclipse.jetty.deploy.providers.ScanningAppProvider$1.fileAdded(ScanningAppProvider.java:64)
at org.eclipse.jetty.util.Scanner.reportAddition(Scanner.java:610)
at org.eclipse.jetty.util.Scanner.reportDifferences(Scanner.java:529)
at org.eclipse.jetty.util.Scanner.scan(Scanner.java:392)
at org.eclipse.jetty.util.Scanner$1.run(Scanner.java:329)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)

Answer 1

Working solution:
public class JettyServerDeploymentManager implements JettyServer {
private static final Logger log = Logger.getLogger(JettyServerDeploymentManager.class.getName());
private Server server;
private DeploymentManager deployer;
private AppProvider appProvider;
static
{
// Make jetty's own logging use java.util.logging
org.eclipse.jetty.util.log.Log.setLog(new JavaUtilLog());
}
public void start() throws Exception {
server = new Server(8090);
// Setup Connector
ServerConnector connector = new ServerConnector(server);
server.setConnectors(new Connector[] {connector});
// Handler Tree location for all webapps
ContextHandlerCollection contexts = new ContextHandlerCollection();
// Handler Tree
HandlerCollection handlers = new HandlerCollection();
handlers.addHandler(contexts);
handlers.addHandler(new DefaultHandler());
server.setHandler(handlers);
// Deployment Manager
DeploymentManager deploymentManager = new DeploymentManager();
deploymentManager.setContexts(contexts);
// App provider
WebAppProvider appProvider = new WebAppProvider();
appProvider.setExtractWars(true); // required for a proper deployment of inner jars
appProvider.setMonitoredDirName("/mytmpdir");
appProvider.setScanInterval(2);
deploymentManager.addAppProvider(appProvider);
server.addBean(deploymentManager);
log.info("starting server");
server.start();
server.join();
}
private static URL findWebAppPath() {
ClassLoader classLoader = SparkApp.class.getClassLoader();
return classLoader.getResource("");
}