NullPointerException when opening socket to localhost
-----------------------------------------------------
Key: DIRMINA-684
URL: https://issues.apache.org/jira/browse/DIRMINA-684
Project: MINA
Issue Type: Bug
Affects Versions: 2.0.0-M4
Environment: Linux
Reporter: David Rosenstrauch
Priority: Minor
I have a MINA-based server I've written that's up and running and works fine.
I recently added a new bit of functionality to it, however, and it's now
throwing NullPointerExceptions intermittently.
The server uses a text-based protocol (using TextLineCodecFactory). I've added
the capability to give the server a command line parm which is the name of a
text file, containing startup commands that the server should execute after it
starts up. I'm doing this by having the server open a java socket to the
server's port on localhost, read the text file and write (and flush) each
command out to the socket.
This is generally working, and the server is receiving and processing each
command (not always in the order sent, but I'm guessing that's an outgrowth of
my using a thread pool, and that's not a problem anyway). But from time to
time, the server is spitting out this error:
SEVERE: EXCEPTION :
org.apache.mina.filter.codec.ProtocolEncoderException:
java.lang.NullPointerException
at
org.apache.mina.filter.codec.ProtocolCodecFilter.filterWrite(ProtocolCodecFilter.java:312)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain.callPreviousFilterWrite(DefaultIoFilterChain.java:506)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1400(DefaultIoFilterChain.java:48)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.filterWrite(DefaultIoFilterChain.java:814)
at
org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:65)
at org.apache.mina.core.session.IoEvent.run(IoEvent.java:64)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTask(OrderedThreadPoolExecutor.java:552)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTasks(OrderedThreadPoolExecutor.java:544)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.run(OrderedThreadPoolExecutor.java:488)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at
org.apache.mina.filter.codec.ProtocolCodecFilter.filterWrite(ProtocolCodecFilter.java:297)
... 9 more
Or sometimes another similar error as well:
SEVERE: Error occurred during message handling
org.apache.mina.filter.codec.ProtocolDecoderException:
java.lang.NullPointerException (Hexdump: 68 65 6C 70 0A 73 74 61 74 73 0A 71 75
65 72 79 20 31 32 33 34 0A)
at
org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:234)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:434)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1200(DefaultIoFilterChain.java:48)
at
org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:802)
at
org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:59)
at org.apache.mina.core.session.IoEvent.run(IoEvent.java:64)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTask(OrderedThreadPoolExecutor.java:552)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTasks(OrderedThreadPoolExecutor.java:544)
at
org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.run(OrderedThreadPoolExecutor.java:488)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at
org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:224)
... 9 more
Noteworthy aspects of my configuration:
* using the M4 release of MINA
* I'm not pausing between sending commands; i.e., I'm write and flushing them
down the socket as quickly as Java can send them
* I'm using both a read and a write thread pool
* building my filter chain as follows:
protocolAcceptor = new NioSocketAcceptor();
protocolAcceptor.setDefaultLocalAddress(new
InetSocketAddress(protocolPort));
protocolAcceptor.setReuseAddress(true);
DefaultIoFilterChainBuilder filterChainBuilder =
protocolAcceptor.getFilterChain();
filterChainBuilder.addLast("logger", new
LoggingFilter(ProfileCacheServer.class));
readerThreadPool = new OrderedThreadPoolExecutor();
filterChainBuilder.addLast("readExecutor", new
ExecutorFilter(readerThreadPool, IoEventType.MESSAGE_RECEIVED));
filterChainBuilder.addLast("codec", new ProtocolCodecFilter(new
TextLineCodecFactory(ParseConstants.UTF8_CHARSET)));
writerThreadPool = new OrderedThreadPoolExecutor();
filterChainBuilder.addLast("writeExecutor", new
ExecutorFilter(writerThreadPool, IoEventType.WRITE));
protocolAcceptor.setHandler(protocolHandler);
I actually did find a way to "fix" this problem but someone on the mailing list
suggested that MINA shouldn't be throwing NPE's regardless. Fix is as follows:
I was originally just dropping the connection on the client side when I was
finished. But after changing my code to issue a proper "close connection"
command to the server before disconnecting, it looks like the NPE's go away.
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