See the polymorphic handling documentation
https://github.com/FasterXML/jackson-annotations?tab=readme-ov-file#handling-polymorphic-types
On Saturday, April 27, 2024 at 3:27:30 PM UTC Mantas Gridinas wrote:
Is @JsonSerialize still around? You could annotate fields with that
annotation and jackson would delegate serializing those fields to that
particular serializer. But your code would remain largely the same - you'd
still need to check what to write depending on the field. I suppose you
could cheat by having that field be some value interface type Foo, and
implementations assigned to that field be FooMap or FooString, where
FooString would have dedicated to string serializer. Deserializing on the
other hand of such structures is painful, but nothing you couldn't handle
with @JsonDeserialize.
On Saturday, April 27, 2024 at 2:08:47 AM UTC Viktor Remennik wrote:
Hi there!
I hope it's a simple question but I cannot find an answer myself. So,
asking for help.
I need to implement custom map serializer when mam mets some condition. the
problem is, that I need to replace the map with a primitive type, e.g.
string. As a simple example - when map conforms to some rule I want to
replace it with, let's say, string value. I understand there could be at
least one case when primitive, like string, cannot be used witout a key.
It's probably if the map is the root node.Maybe I could generate a key for
such a case?
Anyways, I cannot achieve it in any way I tried. Here's the MVE for my
question. I want to make it producing this:
{
"Second" : "Two",
"Third" : "magic string",
"First" : 1
}
instead of default:
{
"Second" : "Two",
"Third" : {
"Eleventh" : 11,
"Twelfth" : "12"
},
"First" : 1
}
Here's the mve itself. Thank you!
public class MapParseTest
{
private final ObjectMapper mapper;
public MapParseTest()
{
mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.setSerializerModifier(new MyMapSerializerModifier());
mapper.registerModule(module);
}
public void doTest() throws JsonProcessingException
{
MyMap map1 = new MyMap();
MyMap map2 = new MyMap();
map1.setName("shtame");
map2.setName("magic name");
map1.put("First", 1);
map1.put("Second", "Two");
map1.put("Third", map2);
map2.put("Eleventh", 11);
map2.put("Twelfth", "12");
String result =
mapper.writerWithDefaultPrettyPrinter().writeValueAsString(map1);
System.*out*.println(result);
}
public static void main(String[] args) throws JsonProcessingException
{
MapParseTest test = new MapParseTest();
test.doTest();
}
@Setter
@Getter
public static class MyMap extends HashMap<String, Object>
{
private String name;
}
public static class MyMapSerializer extends JsonSerializer<MyMap>
{
private final JsonSerializer<Object> defaultSerializer;
public MyMapSerializer(JsonSerializer<Object> defaultSerializer)
{
this.defaultSerializer = defaultSerializer;
}
@Override
public void serialize(MyMap value,
JsonGenerator gen,
SerializerProvider provider) throws
IOException
{
String className = value.getName();
if (className.equalsIgnoreCase("magic name"))
{
gen.writeString("magic string");
} else
{
defaultSerializer.serialize(value, gen, provider);
}
}
}
public static class MyMapSerializerModifier extends
BeanSerializerModifier
{
@Override
public JsonSerializer<?> modifyMapSerializer(SerializationConfig
config,
MapType mapType,
BeanDescription
beanDesc,
JsonSerializer<?>
serializer)
{
Class<?> type = beanDesc.getBeanClass();
if (type.equals(MyMap.class))
{
return new MyMapSerializer((JsonSerializer<Object>)
serializer);
}
return serializer;
}
}
}
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