Deserializing data which can be object or boolean - jaxb

Question

I'm using maven and jersey with the following dependencies
<dependency>
<groupId>org.glassfish.jersey.core</groupId>
<artifactId>jersey-client</artifactId>
<version>2.25</version>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-jackson</artifactId>
<version>2.25</version>
</dependency>
<dependency>
<groupId>org.jvnet.jaxb2_commons</groupId>
<artifactId>jaxb2-basics-annotate</artifactId>
<version>1.0.1</version>
</dependency>
<dependency>
<groupId>org.jvnet.jaxb2_commons</groupId>
<artifactId>jaxb2-basics</artifactId>
<version>0.9.1</version>
</dependency>
I'm using the
maven-jaxb2-plugin
plugin to generate classes from an xsd.
I'm trying to deserialize json which can be received in two ways:
{
"config": {
"field1": 1,
"field2": 2,
"object1": {
.
.
}
}
}
or
{
"config": false
}
For the latter I would expect
{
"config": {}
}
but this is not the case nor do I have influence on that.
When I deserialize this I get an exception
Caused by: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.my.model.ConfigMap out of VALUE_FALSE token
It's clear why I get this exception.
I've been trying to use a custom deserializer to get around this but unsuccessful.
public class ConfigTypeDeserializer extends JsonDeserializer<ConfigType> {
#Override
public ConfigType deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
ObjectCodec cd = jsonParser.getCodec();
JsonNode node = cd.readTree(jsonParser);
ConfigType object = new ObjectFactory().createConfigType();
if (node.isBoolean()) {
return object;
}
// now I know its not a weird response so now I want to deserialize as usual
return object;
}
}
So I check if I see the weird response and if so I return an empty object and if not I want to return the object by deserializing it a usual because the object is too complex to completely build it manually in this deserializer. But I did not find a way to do this. I can e.g. call
cd.readValue(jsonParser,ConfigType.class);
but this does produce a ConfigType object but the contents are not correct. I'm not getting the expected object types.
So I want to know if it is possible to use (or continue) the existing deserialization code from my custom deserializer.
If that is not possible, is there another way to do this?

Answer 1

I found a really neat library
https://github.com/jonpeterson/jackson-module-json-interceptor
With maven:
<dependency>
<groupId>com.github.jonpeterson</groupId>
<artifactId>jackson-module-json-interceptor</artifactId>
<version>1.0.0</version>
</dependency>
which enabled me to intercept the deserialisation process just before it deserialises the object.
You can use this annotation
#JsonInterceptors(beforeDeserialization = {
MyDeserializationInterceptor.class
})
public class MyProblematicObject {
..
}
In my interceptor class I can do this
public class MyDeserializationInterceptor implements JsonInterceptor {
#Override
public JsonNode intercept(JsonNode node, JsonNodeFactory nodeFactory) {
JsonNode config = node.findValue("config");
// convert boolean to object
if (node.isObject() && config.isBoolean()) {
ObjectNode objectNode = nodeFactory.objectNode();
((ObjectNode)node).set("config",objectNode);
}
return node;
}
}
And the deserialisation process happily continues :)
Thank you Jon Peterson !!