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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