I think the problem is here:
On Thu, Dec 20, 2018 at 11:32 AM matt Smith <[email protected]> wrote:
>
> here is the class that I want to serialize.
>
>
> public class ItemRow<T> {
>
> private String id;
> private List<T> items;
> }
>
>
> There are two variations that are allowed.
>
> `ItemRow<String>, ItemRow<ItemRow>`.
>
> In the latter case, it will be nested.
>
> eg:
>
>
> ItemRow item1 = new ItemRow("abc", Arrays.asList("item1", "item2", "item3"));
> String result = mapper.writeValueAsString(item1);
> System.out.println(result);
>
>
>
> should give
>
>
> {"abc":["item1","item2","item3"]}
>
>
>
> Now, the latter case
>
>
> ItemRow item2 = new ItemRow("cde", Arrays.asList("item4, item5"));
> ItemRow item = new ItemRow("combined", Arrays.asList(item1,item2));
> result = mapper.writeValueAsString(item);
> System.out.println(result);
>
>
> should give
>
>
> {
> "combined": {
> "abc": ["item1", "item2", "item3"],
> "cde": ["item4", "item5"]
> }
> }
>
>
> But I get exception while serializing the latter. The first one works as
> expected. so I believe the recursive serialization is failing, but I am
> unable to find out why
>
> Here is exception
>
>
> com.fasterxml.jackson.core.JsonGenerationException: Can not start an object,
> expecting field name (context: Object)
>
> at
> com.fasterxml.jackson.core.JsonGenerator._reportError(JsonGenerator.java:1961)
> at
> com.fasterxml.jackson.core.json.JsonGeneratorImpl._reportCantWriteValueExpectName(JsonGeneratorImpl.java:244)
> at
> com.fasterxml.jackson.core.json.WriterBasedJsonGenerator._verifyValueWrite(WriterBasedJsonGenerator.java:866)
> at
> com.fasterxml.jackson.core.json.WriterBasedJsonGenerator.writeStartObject(WriterBasedJsonGenerator.java:279)
> at hello.ItemRowSerializer.serialize(ItemRow.java:58)
> at hello.ItemRowSerializer.serialize(ItemRow.java:42)
> 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.ObjectMapper.writeValue(ObjectMapper.java:2655)
> at
> com.fasterxml.jackson.core.base.GeneratorBase.writeObject(GeneratorBase.java:381)
> at hello.ItemRowSerializer.serialize(ItemRow.java:67)
> at hello.ItemRowSerializer.serialize(ItemRow.java:42)
>
>
> Serializer implementation
>
>
> class ItemRowSerializer extends JsonSerializer<ItemRow> {
>
> @Override
> public void serialize(ItemRow itemRow, JsonGenerator jgen,
> SerializerProvider serializerProvider) throws IOException {
>
> String id = itemRow.getId();
> List<Object> items = itemRow.getItems();
>
> if (items.isEmpty()) {
> jgen.writeStartObject();
> jgen.writeFieldName(id);
> jgen.writeStartArray();
> jgen.writeEndArray();
> jgen.writeEndObject();
> }
> else {
> jgen.writeStartObject();
> Object item = items.get(0);
> jgen.writeFieldName(id);
> if (item instanceof ItemRow){
> for (Object i : items) {
> //ItemRow temp = (ItemRow) i;
> //jgen.writeObjectField(temp.getId(), temp);
> //jgen.writeObjectField(id, i);
> jgen.writeStartObject();
> jgen.writeObject(i);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
So, `writeStartObject()` will output "{", and then you are trying to
call `writeObject()`
which will end up writing a value of some kind -- but what is expected
at that point is either field name, or closing "}".
So it would seem like you are just missing
jgen.writeFieldName(temp.getId())
or something, or, perhaps you'd want to enclose a sequence of Object
within array,
and need to call
jgen.writeStartArray() / jgen.writeEndArray()
around for loop.
-+ Tatu +-
> jgen.writeEndObject();
> }
> }
> else {
> //jgen.writeFieldName(id);
> jgen.writeStartArray();
> for (Object arg : items) {
> jgen.writeString(arg.toString());
> }
> jgen.writeEndArray();
> }
> }
> jgen.writeEndObject();
> }
> }
>
>
>
>
>
>
>
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