再谈序列化之rpc调用失败和jackson序列化时不允许Map中的key为null

最近遇到了两个序列化相关的问题，比较典型，备忘特此留笔。

1.rpc调用时未进行序列化而导致的rpc调用失败

使用dubbo框架在进行rpc调用的时候，出现了下面的问题，原因是因为接口参数中的NoSerialReqDto类没有实现Serializable接口，没有进行序列化导致的。

Caused by: java.lang.IllegalStateException: Serialized class com.your.package.domain.NoSerialReqDto must implement java.io.Serializable
    at com.alibaba.com.caucho.hessian.io.SerializerFactory.getDefaultSerializer(SerializerFactory.java:395)
    at com.alibaba.com.caucho.hessian.io.SerializerFactory.getSerializer(SerializerFactory.java:369)
    at com.alibaba.com.caucho.hessian.io.Hessian2Output.writeObject(Hessian2Output.java:389)
    at com.alibaba.dubbo.common.serialize.hessian2.Hessian2ObjectOutput.writeObject(Hessian2ObjectOutput.java:88)
    at com.alibaba.dubbo.rpc.protocol.dubbo.DubboCodec.encodeRequestData(DubboCodec.java:176)
    at com.alibaba.dubbo.remoting.exchange.codec.ExchangeCodec.encodeRequest(ExchangeCodec.java:234)
    at com.alibaba.dubbo.remoting.exchange.codec.ExchangeCodec.encode(ExchangeCodec.java:71)
    at com.alibaba.dubbo.rpc.protocol.dubbo.DubboCountCodec.encode(DubboCountCodec.java:38)
    at com.alibaba.dubbo.remoting.transport.netty.NettyCodecAdapter$InternalEncoder.encode(NettyCodecAdapter.java:80)
    at org.jboss.netty.handler.codec.oneone.OneToOneEncoder.handleDownstream(OneToOneEncoder.java:66)
    at com.alibaba.dubbo.remoting.transport.netty.NettyHandler.writeRequested(NettyHandler.java:98)
    at org.jboss.netty.channel.Channels.write(Channels.java:611)
    at org.jboss.netty.channel.Channels.write(Channels.java:578)
    at org.jboss.netty.channel.AbstractChannel.write(AbstractChannel.java:251)
    at com.alibaba.dubbo.remoting.transport.netty.NettyChannel.send(NettyChannel.java:100)
    ... 127 common frames omitted

2.jackson序列化时Map对象中的key不能为Null

Spring Boot中使用Jackson将对象进行序列化时，如果Map对象中的key为null时，会报下面的错误，找到响应的null key，然后将其过滤掉或者进行处理后便可以了。

Caused by: com.fasterxml.jackson.databind.JsonMappingException: Null key for a Map not allowed in JSON (use a converting NullKeySerializer?) (through reference chain: net.your.package.dto.Result\["data"\]->net.your.package.TestNullKeyDto\["testNullKey"\]->net.your.package.TestNullKeyDto\["quantity"\])
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:284)
    at com.fasterxml.jackson.databind.SerializerProvider.mappingException(SerializerProvider.java:1251)
    at com.fasterxml.jackson.databind.SerializerProvider.reportMappingProblem(SerializerProvider.java:1145)
    at com.fasterxml.jackson.databind.ser.impl.FailingSerializer.serialize(FailingSerializer.java:35)
    at com.fasterxml.jackson.databind.ser.std.MapSerializer.serializeFieldsUsing(MapSerializer.java:803)
    at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:637)
    at com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:33)
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
    at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.\_serialize(DefaultSerializerProvider.java:480)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
    at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396)
    at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:913)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:286)
    ... 91 common frames omitted　　

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