Jetty fails to load startup page , throwing null pointer exception

Question

On every hit of an URL it is throwing below null pointer exception. I am using Jetty version jetty-distribution-9.4.18.v20190429

java.lang.NullPointerException
        at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1602)
        at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
        at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
        at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1700)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
        at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
        at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1667)
        at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
        at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
        at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:220)
        at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:152)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
        at org.eclipse.jetty.server.Server.handle(Server.java:505)
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:370)
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:267)
        at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
        at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
        at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:117)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
        at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:698)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:804)
        at java.lang.Thread.run(Unknown Source)

Answer 1

You have a badly defined Filter in your webapp.

Somehow you have a Filter entry, with DispatcherType and url-pattern, but no actual Filter class defined.

Seeing as you don't have ServletContextHandler or WebAppContext in your stacktrace, I'm assuming you are using the raw internal ServletHandler class directly.

The ServletHandler class is very dumb and does very little on it's own, it has to be used from within a ServletContextHandler or the more complex WebAppContext.

A single, raw, ServletHandler can only handle 1 servlet, it has no ServletContext, and cannot participate in a Filter chain.

Would recommend using ServletContextHandler instead of the raw ServletHandler.