Error content:

org.apache.coyote.http11.AbstractHttp11Processor.process Error processing request
 java.lang.NullPointerException
	at org.apache.tomcat.util.buf.CharChunk.append(CharChunk.java:308)
	at org.apache.catalina.mapper.Mapper.map(Mapper.java:683)
	at org.apache.catalina.connector.CoyoteAdapter.postParseRequest(CoyoteAdapter.java:900)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:523)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1100)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:687)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2508)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2497)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

Today, I also had such a problem with Tomcat on the server. I found that it was a null pointer exception reported by the bottom layer of Tomcat. It was said that it was the append method of charchunk class. I was confused for a while. Finally, I looked at the charchunk source code and found that

The error is reported only when the S parameter here is null,

The reason why s is null is that the defaulthostname called from here is null, that is, the method host.Isnull()

The return value is true. If there is no “host” header for an HTTP/1.0 request, host is

Null, and our current Tomcat is basically http/1.1, so this request is unusual and strange. I don’t know when to call it, but it can be solved. It needs to be in server.xml

<Engine name="Catalina" defaultHost="localhost">

Configure one under tab

<Host name="localhost" >
</Host>

In this way, the value of defaulthost will not be ignored and the defaulthostname will have a value, which solves the problem that Tomcat reports a NullPointerException from time to time.