I added as comments beside each line in the else block below. that is what
I expect it to work. is my expectation in any of those lines?
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); //"combined"
if (item instanceof ItemRow){
for (Object i : items) {
jgen.writeStartObject(); // "{"
jgen.writeObject(i); // "abc"
:["item1","item2", "item2"]
jgen.writeEndObject(); // "}"
On Thursday, December 20, 2018 at 11:32:55 AM UTC-8, matt Smith 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);
> jgen.writeEndObject();
> }
> }
> else {
> //jgen.writeFieldName(id);
> jgen.writeStartArray();
> for (Object arg : items) {
> jgen.writeString(arg.toString());
> }
> jgen.writeEndArray();
> }
> }
> jgen.writeEndObject();
> }
> }
>
>
>
>
>
>
>
>
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