retrofit2中嵌套json数组（多类型对象）的JsonDeserializer

Question

我的json响应

[
     [
        {
          "header_id": 1,
          "name" : "Tom",
          "group" : "A"
        },
        {
          "header_id": 2,
          "name" : "Marry",
          "group" : "B"
         }
    ],

    [
         {
             "object_id" : 1,
             "SerialNo" : 123456
         },
         {
             "object_id" : 2,
             "SerialNo" : 89545
         }
     ],

     [
        {
           "workflow_id" : 1,
           "StatusName" : "start"
         },
         {
            "workflow_id" : 2,
            "StatusName" : "end"
          }

    ]
]

public class Header{
    @SerializedName("header_id")
    private int HeaderID;
    @SerializedName("name")
    private String name;
    @SerializedName("group")
    private String group;
}

public class ObjectWork {
    @SerializedName("object_id")
    private int ObjectID;
    @SerializedName("SerialNo")
    private int SerialNo;
}

public class WorkFlow{
    @SerializedName("workflow_id")
    private int WorkflowID;
    @SerializedName("StatusName")
     private String statusName;
}

谢谢

Answer 1

引入一个通用包装器来让Gson识别您的自Gson禁止java.lang.object重写（注意推荐的fieldNamesCaseThatIsAlwaysCamelCase):

abstract class AbstractCommon {
}

final class Header
        extends AbstractCommon {

    @SerializedName("header_id")
    final int headerId = Integer.valueOf(0);

    @SerializedName("name")
    final String name = null;

    @SerializedName("group")
    final String group = null;

    @Override
    public String toString() {
        return headerId + ": " + name;
    }

}

final class ObjectWork
        extends AbstractCommon {

    @SerializedName("object_id")
    final int objectId = Integer.valueOf(0);

    @SerializedName("SerialNo")
    final int serialNo = Integer.valueOf(0);

    @Override
    public String toString() {
        return objectId + ": " + serialNo;
    }

}

final class WorkFlow
        extends AbstractCommon {

    @SerializedName("workflow_id")
    final int workflowId = Integer.valueOf(0);

    @SerializedName("StatusName")
    final String statusName = null;

    @Override
    public String toString() {
        return workflowId + ": " + statusName;
    }

}

现在引入一个JSONDeserializer，它将尝试识别实际类型：

private static final Gson gson = new GsonBuilder()
        .registerTypeAdapter(AbstractCommon.class, (JsonDeserializer<AbstractCommon>) (jsonElement, type, context) -> {
            final JsonObject jsonObject = jsonElement.getAsJsonObject();
            if ( jsonObject.has("header_id") ) {
                return context.deserialize(jsonElement, Header.class);
            }
            if ( jsonObject.has("object_id") ) {
                return context.deserialize(jsonElement, ObjectWork.class);
            }
            if ( jsonObject.has("workflow_id") ) {
                return context.deserialize(jsonElement, WorkFlow.class);
            }
            throw new IllegalArgumentException("Cannot recognize: " + jsonElement);
        })
        .create();

现在您可以轻松地做到：

private static final Type commonsType = new TypeToken<List<List<AbstractCommon>>>() {
}.getType();

public static void main(final String... args)
        throws IOException {
    try ( final JsonReader jsonReader = getPackageResourceJsonReader(Q44034331.class, "arrays.json") ) {
        final List<List<AbstractCommon>> commons = gson.fromJson(jsonReader, commonsType);
        commons.stream()
                .flatMap(Collection::stream)
                .forEach(abstractCommon -> System.out.println(abstractCommon.getClass().getSimpleName() + ": " + abstractCommon));
    }
}

final class Wrapper {

    final Header header;
    final ObjectWork objectWork;
    final WorkFlow workFlow;

    Wrapper(final Header header, final ObjectWork objectWork, final WorkFlow workFlow) {
        this.header = header;
        this.objectWork = objectWork;
        this.workFlow = workFlow;
    }

}

private static Collection<Wrapper> combine(final List<List<AbstractCommon>> commons) {
    @SuppressWarnings({ "unchecked", "rawtypes" })
    final List<Header> headers = (List) commons.get(0);
    @SuppressWarnings({ "unchecked", "rawtypes" })
    final List<ObjectWork> objectWorks = (List) commons.get(1);
    @SuppressWarnings({ "unchecked", "rawtypes" })
    final List<WorkFlow> workFlows = (List) commons.get(2);
    final Iterator<Header> headerIterator = headers.iterator();
    final Iterator<ObjectWork> objectWorkIterator = objectWorks.iterator();
    final Iterator<WorkFlow> workFlowIterator = workFlows.iterator();
    final Collection<Wrapper> wrappers = new ArrayList<>();
    while ( headerIterator.hasNext() && objectWorkIterator.hasNext() && workFlowIterator.hasNext() ) {
        final Header header = headerIterator.next();
        final ObjectWork objectWork = objectWorkIterator.next();
        final WorkFlow workFlow = workFlowIterator.next();
        final Wrapper wrapper = new Wrapper(header, objectWork, workFlow);
        wrappers.add(wrapper);
    }
    return wrappers;
}

combine(commons)
        .forEach(wrapper -> System.out.println(wrapper.header + ", " + wrapper.objectWork + ", " + wrapper.workFlow));

产出：

1:Tom，1:123456，1:Start
2:Marrid，2:89545，2:end