JsonTypeInfo does not serialize when using Jackson with Jersey

问题

I annotated a JAXB class with JsonTypeInfo so that I could serialize polymorphic classes easily. However, the annotation does not show up when serialized by Jersey. To be more specific, it shows up when using ObjectMapper but not as a return type from a resource. I am very confused right now as this seems to be a problem with Jersey => Jackson interaction.

To debug things, I used the jsonfromjaxb example from the jersey-samples to localize my problem. I added the following to the Flights class to have it serialize out to @class.

@JsonTypeInfo(use=JsonTypeInfo.Id.CLASS, include=JsonTypeInfo.As.PROPERTY, property="@class")

I have the following methods available in the resource, one which just returns the JAXB object and one which manually uses ObjectMapper

@GET
@Produces({"application/json"})
public synchronized Flights getFlightList() {
    return myFlights;
}

@GET
@Path("/object_mapper")
@Produces({"application/json"})
public synchronized String getFlights() throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    return mapper.writeValueAsString(myFlights);
}

The result of querying /jsonfromjaxb/flights

{"flight":[{"flightId":"OK123","company":"Czech Airlines","number":123,"aircraft":"B737"},{"flightId":"OK124","company":"Czech Airlines","number":124,"aircraft":"AB115"}]}

The result of querying /jsonfromjaxb/flights/object_mapper

{"@class":"com.sun.jersey.samples.jsonfromjaxb.jaxb.Flights","flight":[{"number":123,"company":"Czech Airlines","aircraft":"B737","flightId":"OK123"},{"number":124,"company":"Czech Airlines","aircraft":"AB115","flightId":"OK124"}]}

Thanks, Ransom

回答1:

I think it looks like you aren't using Jackson-based serialization (that is, one that uses ObjectMapper; low-level jackson generator is used for most JSON output, including ones where binding is done differently). If you were, it definitely should look like what you see from explicit use. So it seems to be matter of changing Jersey JSON configuration.

来源：https://stackoverflow.com/questions/4899397/jsontypeinfo-does-not-serialize-when-using-jackson-with-jersey

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java

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jaxb

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jackson