近期发现线上的一个dubbo网关类应用在解析后端接口RpcException时出现了反序列化失败问题，小编花了一些心思最终解决了该问题，同时小编也认为该问题比较具有代表性，有必要拿出来和大家一起分享下解决过程。
后端接口异常信息如下：
{"@type": "com.alibaba.dubbo.rpc.RpcException","biz": false,"cause": {"@type": "com.alibaba.dubbo.remoting.RemotingException","localAddress": {"address": "172.31.6.206","port": 63608},"localizedMessage": "java.lang.NullPointerException\njava.lang.NullPointerException\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize0(PojoUtils.java:368)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:204)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:90)\n\tat com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:65)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)\n\tat com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)\n\tat com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\tat java.lang.Thread.run(Thread.java:748)\n","message": "java.lang.NullPointerException\njava.lang.NullPointerException\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize0(PojoUtils.java:368)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:204)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:90)\n\tat com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:65)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)\n\tat com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)\n\tat com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\tat java.lang.Thread.run(Thread.java:748)\n","remoteAddress": {"address": "10.31.31.181","port": 48242},"stackTrace": [{"className": "com.alibaba.dubbo.remoting.exchange.support.DefaultFuture","fileName": "DefaultFuture.java","lineNumber": 245,"methodName": "returnFromResponse","nativeMethod": false},{"className": "com.alibaba.dubbo.remoting.exchange.support.DefaultFuture","fileName": "DefaultFuture.java","lineNumber": 162,"methodName": "get","nativeMethod": false},{"className": "com.alibaba.dubbo.remoting.exchange.support.DefaultFuture","fileName": "DefaultFuture.java","lineNumber": 135,"methodName": "get","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.dubbo.DubboInvoker","fileName": "DubboInvoker.java","lineNumber": 95,"methodName": "doInvoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.AbstractInvoker","fileName": "AbstractInvoker.java","lineNumber": 155,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.filter.GenericImplFilter","fileName": "GenericImplFilter.java","lineNumber": 172,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.csp.sentinel.adapter.dubbo.SentinelDubboConsumerFilter","fileName": "SentinelDubboConsumerFilter.java","lineNumber": 60,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "cn.gov.zcy.zeye.dubbo.client.EagleyeDubboFilter","fileName": "EagleyeDubboFilter.java","lineNumber": 162,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.monitor.support.MonitorFilter","fileName": "MonitorFilter.java","lineNumber": 75,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.csp.sentinel.adapter.dubbo.DubboAppContextFilter","fileName": "DubboAppContextFilter.java","lineNumber": 41,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.dubbo.filter.FutureFilter","fileName": "FutureFilter.java","lineNumber": 54,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.filter.ConsumerContextFilter","fileName": "ConsumerContextFilter.java","lineNumber": 49,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1","fileName": "ProtocolFilterWrapper.java","lineNumber": 72,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.listener.ListenerInvokerWrapper","fileName": "ListenerInvokerWrapper.java","lineNumber": 77,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.protocol.InvokerWrapper","fileName": "InvokerWrapper.java","lineNumber": 56,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.cluster.support.FailoverClusterInvoker","fileName": "FailoverClusterInvoker.java","lineNumber": 78,"methodName": "doInvoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker","fileName": "AbstractClusterInvoker.java","lineNumber": 244,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker","fileName": "MockClusterInvoker.java","lineNumber": 75,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler","fileName": "InvokerInvocationHandler.java","lineNumber": 52,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.common.bytecode.proxy0","fileName": "proxy0.java","lineNumber": -1,"methodName": "$invoke","nativeMethod": false},{"className": "org.apache.dubbo.proxy.service.GenericInvoke","fileName": "GenericInvoke.java","lineNumber": 58,"methodName": "genericCall","nativeMethod": false},{"className": "org.apache.dubbo.proxy.worker.RequestWorker","fileName": "RequestWorker.java","lineNumber": 85,"methodName": "run","nativeMethod": false},{"className": "java.util.concurrent.ThreadPoolExecutor","fileName": "ThreadPoolExecutor.java","lineNumber": 1142,"methodName": "runWorker","nativeMethod": false},{"className": "java.util.concurrent.ThreadPoolExecutor$Worker","fileName": "ThreadPoolExecutor.java","lineNumber": 617,"methodName": "run","nativeMethod": false},{"className": "java.lang.Thread","fileName": "Thread.java","lineNumber": 745,"methodName": "run","nativeMethod": false}]},"code": 0,"forbidded": false,"localizedMessage": "Failed to invoke the method $invoke in the service com.alibaba.dubbo.rpc.service.GenericService. Tried 3 times of the providers [10.31.31.181:48242, 10.31.16.150:31936] (2/2) from the registry 172.31.2.166:1500 on the consumer 172.31.6.206 using the dubbo version 2.6.5. Last error is: Failed to invoke remote method: $invoke, provider: dubbo://10.31.31.181:48242/cn.gov.zcy.service.brand.service.BrandReadService?anyhost=true&application=dubbo-proxy&check=false&dubbo=2.5.3&generic=true&heartbeat=10000&interface=cn.gov.zcy.service.brand.service.BrandReadService&logger=slf4j&methods=findByFullNameList,pagination,getBrands,paginationByAdmin,findByCategoryCodeSet,findSingleBrand,findBrandList,paginationWithInstitution,getChangeDetail,queryBrandAuditLog,findListByName,findById,findByIds,pageQueryAudit,findByName,getFinalBrandDetail,findByCategoryCode,exist,findByCategoryCodeAndName,getAllBrand,filterBrand,findByFullName,findByNamePrefix,findCachedByName&pid=10978®ister.ip=172.31.6.206&remote.timestamp=1596185263797&retries=2&revision=1.0.0&service.filter=dubboFilter&side=consumer&timeout=10000×tamp=1594202613252&version=1.0.0, cause: java.lang.NullPointerException\njava.lang.NullPointerException\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize0(PojoUtils.java:368)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:204)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:90)\n\tat com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:65)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)\n\tat com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)\n\tat com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\tat java.lang.Thread.run(Thread.java:748)\n","message": "Failed to invoke the method $invoke in the service com.alibaba.dubbo.rpc.service.GenericService. Tried 3 times of the providers [10.31.31.181:48242, 10.31.16.150:31936] (2/2) from the registry 172.31.2.166:1500 on the consumer 172.31.6.206 using the dubbo version 2.6.5. Last error is: Failed to invoke remote method: $invoke, provider: dubbo://10.31.31.181:48242/cn.gov.zcy.service.brand.service.BrandReadService?anyhost=true&application=dubbo-proxy&check=false&dubbo=2.5.3&generic=true&heartbeat=10000&interface=cn.gov.zcy.service.brand.service.BrandReadService&logger=slf4j&methods=findByFullNameList,pagination,getBrands,paginationByAdmin,findByCategoryCodeSet,findSingleBrand,findBrandList,paginationWithInstitution,getChangeDetail,queryBrandAuditLog,findListByName,findById,findByIds,pageQueryAudit,findByName,getFinalBrandDetail,findByCategoryCode,exist,findByCategoryCodeAndName,getAllBrand,filterBrand,findByFullName,findByNamePrefix,findCachedByName&pid=10978®ister.ip=172.31.6.206&remote.timestamp=1596185263797&retries=2&revision=1.0.0&service.filter=dubboFilter&side=consumer&timeout=10000×tamp=1594202613252&version=1.0.0, cause: java.lang.NullPointerException\njava.lang.NullPointerException\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize0(PojoUtils.java:368)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:204)\n\tat com.alibaba.dubbo.common.utils.PojoUtils.realize(PojoUtils.java:90)\n\tat com.alibaba.dubbo.rpc.filter.GenericFilter.invoke(GenericFilter.java:65)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke(ClassLoaderFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.filter.EchoFilter.invoke(EchoFilter.java:38)\n\tat com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:91)\n\tat com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply(DubboProtocol.java:108)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest(HeaderExchangeHandler.java:84)\n\tat com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received(HeaderExchangeHandler.java:170)\n\tat com.alibaba.dubbo.remoting.transport.DecodeHandler.received(DecodeHandler.java:52)\n\tat com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run(ChannelEventRunnable.java:82)\n\tat java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)\n\tat java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)\n\tat java.lang.Thread.run(Thread.java:748)\n","network": true,"serialization": false,"stackTrace": [{"className": "com.alibaba.dubbo.rpc.cluster.support.FailoverClusterInvoker","fileName": "FailoverClusterInvoker.java","lineNumber": 109,"methodName": "doInvoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker","fileName": "AbstractClusterInvoker.java","lineNumber": 244,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker","fileName": "MockClusterInvoker.java","lineNumber": 75,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler","fileName": "InvokerInvocationHandler.java","lineNumber": 52,"methodName": "invoke","nativeMethod": false},{"className": "com.alibaba.dubbo.common.bytecode.proxy0","fileName": "proxy0.java","lineNumber": -1,"methodName": "$invoke","nativeMethod": false},{"className": "org.apache.dubbo.proxy.service.GenericInvoke","fileName": "GenericInvoke.java","lineNumber": 58,"methodName": "genericCall","nativeMethod": false},{"className": "org.apache.dubbo.proxy.worker.RequestWorker","fileName": "RequestWorker.java","lineNumber": 85,"methodName": "run","nativeMethod": false},{"className": "java.util.concurrent.ThreadPoolExecutor","fileName": "ThreadPoolExecutor.java","lineNumber": 1142,"methodName": "runWorker","nativeMethod": false},{"className": "java.util.concurrent.ThreadPoolExecutor$Worker","fileName": "ThreadPoolExecutor.java","lineNumber": 617,"methodName": "run","nativeMethod": false},{"className": "java.lang.Thread","fileName": "Thread.java","lineNumber": 745,"methodName": "run","nativeMethod": false}],"timeout": false}
仔细看异常信息，实际上真实的异常信息应该是"java.lang.NullPointerException\njava.lang.NullPointerException"，但是经过dubbo框架层层包装成了RpcException。
当我们拿到以上异常信息的字符串后，应该如何转换为RpcException，使用Fastjson库代码如下：
RpcException exception = JSON.parseObject(result.getBytes(), RpcException.class, Feature.IgnoreNotMatch);System.out.println(exception);
代码非常的简单，但是很遗憾，以上代码会报错：
Exception in thread "main" com.alibaba.fastjson.JSONException: set property error, com.alibaba.dubbo.remoting.RemotingException#localAddressat com.alibaba.fastjson.parser.deserializer.FieldDeserializer.setValue(FieldDeserializer.java:183)at com.alibaba.fastjson.parser.deserializer.ThrowableDeserializer.deserialze(ThrowableDeserializer.java:149)at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:688)at com.alibaba.fastjson.JSON.parseObject(JSON.java:396)at com.alibaba.fastjson.JSON.parseObject(JSON.java:300)at com.alibaba.fastjson.JSON.parseObject(JSON.java:573)at cn.gov.zcy.dubbotest.controller.TestController.main(TestController.java:520)Caused by: java.lang.IllegalArgumentException: Can not set java.net.InetSocketAddress field com.alibaba.dubbo.remoting.RemotingException.localAddress to java.lang.Exceptionat sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:75)at java.lang.reflect.Field.set(Field.java:764)at com.alibaba.fastjson.parser.deserializer.FieldDeserializer.setValue(FieldDeserializer.java:178)... 6 more
异常信息明确提示了"Can not set java.net.InetSocketAddress field com.alibaba.dubbo.remoting.RemotingException.localAddress to java.lang.Exception"。
接口异常信息中@type字段明确指明了该以上为RpcException，这里为什么还会报上述异常呢？带着这个问题，我们来看看com.alibaba.dubbo.remoting.RemotingException.localAddress属性到底是如何定义的呢。
public class RemotingException extends Exception {private static final long serialVersionUID = -3160452149606778709L;private InetSocketAddress localAddress;private InetSocketAddress remoteAddress;// ...此处省略1w行代码...}
RemotingException的属性localAddress和remoteAddress均为InetSocketAddress类型。而InetSocketAddress是jdk 1.4就已经原生提供的类了。
/**** This class implements an IP Socket Address (IP address + port number)* It can also be a pair (hostname + port number), in which case an attempt* will be made to resolve the hostname. If resolution fails then the address* is said to be <I>unresolved</I> but can still be used on some circumstances* like connecting through a proxy.* <p>* It provides an immutable object used by sockets for binding, connecting, or* as returned values.* <p>* The <i>wildcard</i> is a special local IP address. It usually means "any"* and can only be used for {@code bind} operations.** @see java.net.Socket* @see java.net.ServerSocket* @since 1.4*/public class InetSocketAddressextends SocketAddress{// Private implementation class pointed to by all public methods.private static class InetSocketAddressHolder {// The hostname of the Socket Addressprivate String hostname;// The IP address of the Socket Addressprivate InetAddress addr;// The port number of the Socket Addressprivate int port;private InetSocketAddressHolder(String hostname, InetAddress addr, int port) {this.hostname = hostname;this.addr = addr;this.port = port;}private int getPort() {return port;}private InetAddress getAddress() {return addr;}private String getHostName() {if (hostname != null)return hostname;if (addr != null)return addr.getHostName();return null;}private String getHostString() {if (hostname != null)return hostname;if (addr != null) {if (addr.holder().getHostName() != null)return addr.holder().getHostName();elsereturn addr.getHostAddress();}return null;}private boolean isUnresolved() {return addr == null;}@Overridepublic String toString() {if (isUnresolved()) {return hostname + ":" + port;} else {return addr.toString() + ":" + port;}}@Overridepublic final boolean equals(Object obj) {if (obj == null || !(obj instanceof InetSocketAddressHolder))return false;InetSocketAddressHolder that = (InetSocketAddressHolder)obj;boolean sameIP;if (addr != null)sameIP = addr.equals(that.addr);else if (hostname != null)sameIP = (that.addr == null) &&hostname.equalsIgnoreCase(that.hostname);elsesameIP = (that.addr == null) && (that.hostname == null);return sameIP && (port == that.port);}@Overridepublic final int hashCode() {if (addr != null)return addr.hashCode() + port;if (hostname != null)return hostname.toLowerCase().hashCode() + port;return port;}}private final transient InetSocketAddressHolder holder;private static final long serialVersionUID = 5076001401234631237L;private static int checkPort(int port) {if (port < 0 || port > 0xFFFF)throw new IllegalArgumentException("port out of range:" + port);return port;}private static String checkHost(String hostname) {if (hostname == null)throw new IllegalArgumentException("hostname can't be null");return hostname;}/*** Creates a socket address where the IP address is the wildcard address* and the port number a specified value.* <p>* A valid port value is between 0 and 65535.* A port number of {@code zero} will let the system pick up an* ephemeral port in a {@code bind} operation.* <p>* @param port The port number* @throws IllegalArgumentException if the port parameter is outside the specified* range of valid port values.*/public InetSocketAddress(int port) {this(InetAddress.anyLocalAddress(), port);}/**** Creates a socket address from an IP address and a port number.* <p>* A valid port value is between 0 and 65535.* A port number of {@code zero} will let the system pick up an* ephemeral port in a {@code bind} operation.* <P>* A {@code null} address will assign the <i>wildcard</i> address.* <p>* @param addr The IP address* @param port The port number* @throws IllegalArgumentException if the port parameter is outside the specified* range of valid port values.*/public InetSocketAddress(InetAddress addr, int port) {holder = new InetSocketAddressHolder(null,addr == null ? InetAddress.anyLocalAddress() : addr,checkPort(port));}/**** Creates a socket address from a hostname and a port number.* <p>* An attempt will be made to resolve the hostname into an InetAddress.* If that attempt fails, the address will be flagged as <I>unresolved</I>.* <p>* If there is a security manager, its {@code checkConnect} method* is called with the host name as its argument to check the permission* to resolve it. This could result in a SecurityException.* <P>* A valid port value is between 0 and 65535.* A port number of {@code zero} will let the system pick up an* ephemeral port in a {@code bind} operation.* <P>* @param hostname the Host name* @param port The port number* @throws IllegalArgumentException if the port parameter is outside the range* of valid port values, or if the hostname parameter is <TT>null</TT>.* @throws SecurityException if a security manager is present and* permission to resolve the host name is* denied.* @see #isUnresolved()*/public InetSocketAddress(String hostname, int port) {checkHost(hostname);InetAddress addr = null;String host = null;try {addr = InetAddress.getByName(hostname);} catch(UnknownHostException e) {host = hostname;}holder = new InetSocketAddressHolder(host, addr, checkPort(port));}// private constructor for creating unresolved instancesprivate InetSocketAddress(int port, String hostname) {holder = new InetSocketAddressHolder(hostname, null, port);}/**** Creates an unresolved socket address from a hostname and a port number.* <p>* No attempt will be made to resolve the hostname into an InetAddress.* The address will be flagged as <I>unresolved</I>.* <p>* A valid port value is between 0 and 65535.* A port number of {@code zero} will let the system pick up an* ephemeral port in a {@code bind} operation.* <P>* @param host the Host name* @param port The port number* @throws IllegalArgumentException if the port parameter is outside* the range of valid port values, or if the hostname* parameter is <TT>null</TT>.* @see #isUnresolved()* @return a {@code InetSocketAddress} representing the unresolved* socket address* @since 1.5*/public static InetSocketAddress createUnresolved(String host, int port) {return new InetSocketAddress(checkPort(port), checkHost(host));}/*** @serialField hostname String* @serialField addr InetAddress* @serialField port int*/private static final ObjectStreamField[] serialPersistentFields = {new ObjectStreamField("hostname", String.class),new ObjectStreamField("addr", InetAddress.class),new ObjectStreamField("port", int.class)};private void writeObject(ObjectOutputStream out)throws IOException{// Don't call defaultWriteObject()ObjectOutputStream.PutField pfields = out.putFields();pfields.put("hostname", holder.hostname);pfields.put("addr", holder.addr);pfields.put("port", holder.port);out.writeFields();}private void readObject(ObjectInputStream in)throws IOException, ClassNotFoundException{// Don't call defaultReadObject()ObjectInputStream.GetField oisFields = in.readFields();final String oisHostname = (String)oisFields.get("hostname", null);final InetAddress oisAddr = (InetAddress)oisFields.get("addr", null);final int oisPort = oisFields.get("port", -1);// Check that our invariants are satisfiedcheckPort(oisPort);if (oisHostname == null && oisAddr == null)throw new InvalidObjectException("hostname and addr " +"can't both be null");InetSocketAddressHolder h = new InetSocketAddressHolder(oisHostname,oisAddr,oisPort);UNSAFE.putObject(this, FIELDS_OFFSET, h);}private void readObjectNoData()throws ObjectStreamException{throw new InvalidObjectException("Stream data required");}private static final long FIELDS_OFFSET;private static final sun.misc.Unsafe UNSAFE;static {try {sun.misc.Unsafe unsafe = sun.misc.Unsafe.getUnsafe();FIELDS_OFFSET = unsafe.objectFieldOffset(InetSocketAddress.class.getDeclaredField("holder"));UNSAFE = unsafe;} catch (ReflectiveOperationException e) {throw new Error(e);}}/*** Gets the port number.** @return the port number.*/public final int getPort() {return holder.getPort();}/**** Gets the {@code InetAddress}.** @return the InetAdress or {@code null} if it is unresolved.*/public final InetAddress getAddress() {return holder.getAddress();}/*** Gets the {@code hostname}.* Note: This method may trigger a name service reverse lookup if the* address was created with a literal IP address.** @return the hostname part of the address.*/public final String getHostName() {return holder.getHostName();}/*** Returns the hostname, or the String form of the address if it* doesn't have a hostname (it was created using a literal).* This has the benefit of <b>not</b> attempting a reverse lookup.** @return the hostname, or String representation of the address.* @since 1.7*/public final String getHostString() {return holder.getHostString();}/*** Checks whether the address has been resolved or not.** @return {@code true} if the hostname couldn't be resolved into* an {@code InetAddress}.*/public final boolean isUnresolved() {return holder.isUnresolved();}/*** Constructs a string representation of this InetSocketAddress.* This String is constructed by calling toString() on the InetAddress* and concatenating the port number (with a colon). If the address* is unresolved then the part before the colon will only contain the hostname.** @return a string representation of this object.*/@Overridepublic String toString() {return holder.toString();}/*** Compares this object against the specified object.* The result is {@code true} if and only if the argument is* not {@code null} and it represents the same address as* this object.* <p>* Two instances of {@code InetSocketAddress} represent the same* address if both the InetAddresses (or hostnames if it is unresolved) and port* numbers are equal.* If both addresses are unresolved, then the hostname and the port number* are compared.** Note: Hostnames are case insensitive. e.g. "FooBar" and "foobar" are* considered equal.** @param obj the object to compare against.* @return {@code true} if the objects are the same;* {@code false} otherwise.* @see java.net.InetAddress#equals(java.lang.Object)*/@Overridepublic final boolean equals(Object obj) {if (obj == null || !(obj instanceof InetSocketAddress))return false;return holder.equals(((InetSocketAddress) obj).holder);}/*** Returns a hashcode for this socket address.** @return a hash code value for this socket address.*/@Overridepublic final int hashCode() {return holder.hashCode();}}
仔细阅读InetSocketAddress的代码，我们发现其address和port属性并无set方法。其对象实例是通过constructor传参的方式直接生成的。
小编写了一段测试代码：
RemotingException e = new RemotingException(new InetSocketAddress("127.0.0.1", 11111), new InetSocketAddress("127.0.0.1", 22222), "xxxxx");String s = JSON.toJSONString(e);System.out.println(s);System.out.println("================");RemotingException e1 = JSON.parseObject(s, RemotingException.class);System.out.println(e1);
可以看到，序列化没问题，但是反序列化时输出了跟RpcException反序列化一样的错误信息：
{"@type":"com.alibaba.dubbo.remoting.RemotingException","localAddress":{"address":"127.0.0.1","port":11111},"localizedMessage":"xxxxx","message":"xxxxx","remoteAddress":{"address":"127.0.0.1","port":22222},"stackTrace":[{"className":"cn.gov.zcy.dubbotest.controller.TestController","fileName":"TestController.java","lineNumber":516,"methodName":"main","nativeMethod":false}]}================Exception in thread "main" com.alibaba.fastjson.JSONException: set property error, com.alibaba.dubbo.remoting.RemotingException#localAddressat com.alibaba.fastjson.parser.deserializer.FieldDeserializer.setValue(FieldDeserializer.java:183)at com.alibaba.fastjson.parser.deserializer.ThrowableDeserializer.deserialze(ThrowableDeserializer.java:149)at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:688)at com.alibaba.fastjson.JSON.parseObject(JSON.java:396)at com.alibaba.fastjson.JSON.parseObject(JSON.java:300)at com.alibaba.fastjson.JSON.parseObject(JSON.java:573)at cn.gov.zcy.dubbotest.controller.TestController.main(TestController.java:520)Caused by: java.lang.IllegalArgumentException: Can not set java.net.InetSocketAddress field com.alibaba.dubbo.remoting.RemotingException.localAddress to java.lang.Exceptionat sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)at sun.reflect.UnsafeObjectFieldAccessorImpl.set(UnsafeObjectFieldAccessorImpl.java:75)at java.lang.reflect.Field.set(Field.java:764)at com.alibaba.fastjson.parser.deserializer.FieldDeserializer.setValue(FieldDeserializer.java:178)... 6 more
实际上InetSocketAddress和InetAddress都不能用作Java Bean，也不能进行字符串反序列化。这就是今天这个问题的本质了。那有什么办法可以避免这个问题呢？
第一个想到思路的就是fastjson的反序列化是忽略转换失败的字段，但是很遗憾，目前fastjson并不支持，具体信息小伙伴可以看github issue说明：https://github.com/alibaba/fastjson/issues/854。
第二个想到的思路是忽略不匹配的字段，及当json key找不到映射关系时不进行转换。
RpcException exception = JSON.parseObject(result.getBytes(), RpcException.class, Feature.IgnoreNotMatch);System.out.println(exception);
但是，实际上RpcException的json key是匹配的，怎么进行忽略呢？小编的解决方法很简单，直接使用字符串替换将localAddress替换为localAddress0。同理，将remoteAddress替换为remoteAddress0，人为制造了字段不匹配。
当然了，小编今天讲到的解决方法也只是小编不得已而为之，至于dubbo框架为什么在RemotingException类中使用InetSocketAddress小编暂时还不得而知。也许在将来小编会找到更优的解决方法，到时小编再拿出来分享给小伙伴们。
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