[Solved] Error: exception: java.lang.reflect.InvocationTargetException: null

Error background

Java code occasionally reports an error, but it will not report an error under normal circumstances.

Error

exception: java.lang.reflect.InvocationTargetException: null

2020-05-11 at 15:17:39 CST traceId:[] ERROR io.netty.util.internal.logging.AbstractInternalLogger 91 error-Unexpected exception: java.lang.reflect.InvocationTargetException: null 
    at sun.reflect.GeneratedMethodAccessor214. invoke(Unknown Source) ~[?:? ]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java: 43) ~[?:1.8 .0_192]
    at java.lang.reflect.Method.invoke(Method.java: 498) ~[?:1.8 .0_192]
    at org.yeauty.pojo.PojoEndpointServer.doOnClose(PojoEndpointServer.java: 121) [netty-websocket-spring-boot-starter-0.8.0.jar!/:? ]
    at org.yeauty.standard.WebSocketServerHandler.channelInactive(WebSocketServerHandler.java: 29) [netty-websocket-spring-boot-starter-0.8.0.jar!/:? ]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 257) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 243) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java: 236) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.handler.codec.ByteToMessageDecoder.channelInputClosed(ByteToMessageDecoder.java: 393) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.handler.codec.ByteToMessageDecoder.channelInactive(ByteToMessageDecoder.java: 358) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 257) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 243) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelInactive(AbstractChannelHandlerContext.java: 236) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelInactive(DefaultChannelPipeline.java: 1416) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 257) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelInactive(AbstractChannelHandlerContext.java: 243) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.DefaultChannelPipeline.fireChannelInactive(DefaultChannelPipeline.java: 912) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.AbstractChannel$AbstractUnsafe$ 8.run(AbstractChannel.java:816) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java: 163) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java: 416) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java: 515) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor$ 5.run(SingleThreadEventExecutor.java:918) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.util.internal.ThreadExecutorMap$ 2.run(ThreadExecutorMap.java:74) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java: 30) [netty-all-4.1.38.Final.jar!/:4.1.38 .Final]
    at java.lang.Thread.run(Thread.java: 748) [?:1.8 .0_192]
Caused by: java.util.ConcurrentModificationException
    at java.util.HashMap$HashIterator.nextNode(HashMap.java: 1445) ~[?:1.8 .0_192]
    at java.util.HashMap$EntryIterator.next(HashMap.java: 1479) ~[?:1.8 .0_192]
    at java.util.HashMap$EntryIterator.next(HashMap.java: 1477) ~[?:1.8 .0_192]
    at com.jcdz.hbdservice.websocket.ServerWebSocket1.onClose(ServerWebSocket1.java: 38) ~[coalminehbdservice-1.0.jar!/:1.0 ]
    ... 25 more

Reason for error

There are many reasons for the error, I will only say the reason I came into contact:

(1) If (==) judgment statement is wrong

if( devMap. getOrDefault ( “locationcode”,”” ) == null )

devMap.get( “locationcode” ) : It is possible that a null is passed, and a null pointer will appear at this time

View the source code of getOrDefault()

1  /** 
2       * Returns the value to which the specified key is mapped, or
 3       * { @code defaultValue} if this map contains no mapping for the key.
 4       *
 5       * @implSpec
 6       * The default implementation makes no guarantees about synchronization
 7       * or atomicity properties of this method. Any implementation providing
 8       * atomicity guarantees must override this method and document its
 9       * concurrency properties.
 10       *
 11       * @param key the key whose associated value is to be returned
12       * @param defaultValue the default mapping of the key
 13       * @return the value to which the specified key is mapped, or
 14       * { @code defaultValue} if this map contains no mapping for the key
 15       * @throws ClassCastException if the key AN of inappropriate type for IS
 16       * the this Map
 . 17       * (<a href="{@%20docroot%20}/java/util/Collection.html#optional-restrictions"> optional </a>)
 18 is       * @throws a NullPointerException IF The specified key is null and this map
 19      * does not permit null keys
 20       * (<a href="{@%20docRoot%20}/java/util/Collection.html#optional-restrictions">optional</a>)
 21       * @since 1.8
 22       */ 
23      default V getOrDefault (Object key, V defaultValue) {
 24          V v;
 25          return (((v = get(key)) != null ) || containsKey(key))
 26              ? V
 27              : defaultValue;
 28      }

@throws NullPointerException if the specified key is null and this map does not allow null keys

We can see that there is a get(key) method in the getOrDefault () method. At this time, if the value of key is a null, an error will be reported, such as key:null.

When the value of map is passed in, it is necessary to avoid the phenomenon of passing in map.put(key: null). You can use map.put(key: “”) instead.

(2) if (equals) judgment statement is wrong

if(! time .equals( “1900-01-01 00:00:00” ))

time : it is possible to pass a null, then there will be a null pointer phenomenon

Error resolution

Modify the sequence of judgment statements as follows:

if( null == devMap getOrDefault ( “locationcode”,”” ))

if(! “1900-01-01 00:00:00”.equals(time))


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