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PONested Classes that need custom Jackson deserializer
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  1. PONested Classes that need custom Jackson deserializer
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    copied!<p>I have a light wrapper class around a complex class for which I needed to write a custom Jackson JSON deserializer. The wrapper class is simple and only contains a String, a Date, and my complex object as properties. Does Jackson automatically apply a simple deserializer to the wrapper and my custom deserializer to my complex object? The custom deserializer works by itself. But when I try to serialize the wrapper Jackson throws a Nullpointer Exception. I must be missing something conceptual. Do I have to register another serializer with my module in addition to my custom deserializer?</p> <pre><code>java.lang.NullPointerException at org.codehaus.jackson.impl.ReaderBasedParser._skipWSOrEnd(ReaderBasedParser.java:1477) at org.codehaus.jackson.impl.ReaderBasedParser.nextToken(ReaderBasedParser.java:368) at org.codehaus.jackson.map.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:690) at org.codehaus.jackson.map.deser.BeanDeserializer.deserialize(BeanDeserializer.java:580) at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2732) at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1863) at com.newoak.noc.curve.model.tests.ModelParamsTest.deserializeGraph(ModelParamsTest.java:100) at com.newoak.noc.curve.model.tests.ModelParamsTest.testSerializationDeserialization(ModelParamsTest.java:113) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) </code></pre> <p><strong>Trying to deserialize</strong></p> <pre><code>public ModelParamGraph deserializeGraph(String json) throws JsonGenerationException, JsonMappingException, IOException { ObjectMapper mapper = new ObjectMapper(); SimpleModule testModule = new SimpleModule("MyModule", new Version(1, 0, 0, null)); testModule.addSerializer(new SpaceJsonSerializer()); testModule.addDeserializer(Space.class, new SpaceJsonDeserializer()); mapper.registerModule(testModule); ModelParamGraph space = mapper.readValue(json, ModelParamGraph.class); return space; } </code></pre> <p><strong>Wrapper</strong></p> <pre><code>public class ModelParamGraph { public String source; public Date date; @JsonSerialize(using=SpaceJsonSerializer.class) @JsonDeserialize(using=SpaceJsonDeserializer.class) public Space&lt;TModelParam&gt; paramSpace; public ModelParamGraph() { } public ModelParamGraph(String source, Date date) { setSource(source); setDate(date); setParamSpace(new Space&lt;TModelParam&gt;()); } //getters and setters } </code></pre>
 

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