Skip objects conditionally when serializing with jackson
I have a class like
interface IHideable {
boolean isHidden();
}
class Address implements IHideable {
private String city;
private String street;
private boolean hidden;
}
class PersonalInfo implements IHideable {
private String name;
private int age;
private boolean hidden;
}
I want to serialize IHideable list in my webservice; but filter out any object that has a hidden field set to true.
Mostly given with a list of objects like
[
{'city 1','street 1',false},
{'city 2','street 2',true},
{'city 3','street 3',false}
]
I want the result to be
[
{
city:'city 1',
street:'street 1'
},
{
city:'city 3',
street:'street 3'
}
]
I tried the following implementation
class ItemSerializer extends JsonSerializer<IHideable> {
@Override
public void serialize(IHideable value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
if (!value.isHidden()) {
jgen.writeStartObject();
jgen.writeString("city", value.city);
jgen.writeString("street", value.street);
jgen.writeEndObject();
}
}
}
But the written methods writeString are specific to the Address class. When I use writeObject it throws stackoverflow exception. Can I use some generic writeObject method that any object that implements IHideable () can write? Is this possible using Jackson's standard / standard serialization?
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You can use BeanSerializerModifier
to register a serializer for types IHideable
and get a reference to the default serializer bean as discussed in this question.
In your serializer, you are checking the flag isHidden
and not setting serialization of the instance with the default serializer. This trick should work for any type that implements your interface IHideable
. Here's an example:
public class JacksonHide {
@JsonIgnoreProperties("hidden")
public static interface IHideable {
boolean isHidden();
}
public static class Address implements IHideable {
public final String city;
public final String street;
public final boolean hidden;
public Address(String city, String street, boolean hidden) {
this.city = city;
this.street = street;
this.hidden = hidden;
}
@Override
public boolean isHidden() {
return hidden;
}
}
public static class PersonalInfo implements IHideable {
public final String name;
public final int age;
public final boolean hidden;
public PersonalInfo(String name, int age, boolean hidden) {
this.name = name;
this.age = age;
this.hidden = hidden;
}
@Override
public boolean isHidden() {
return hidden;
}
}
private static class MyBeanSerializerModifier extends BeanSerializerModifier {
@Override
public JsonSerializer<?> modifySerializer(SerializationConfig config,
BeanDescription beanDesc,
JsonSerializer<?> serializer) {
if (IHideable.class.isAssignableFrom(beanDesc.getBeanClass())) {
return new MyIHideableJsonSerializer((JsonSerializer<IHideable>) serializer);
}
return super.modifySerializer(config, beanDesc, serializer);
}
private static class MyIHideableJsonSerializer extends JsonSerializer<IHideable> {
private final JsonSerializer<IHideable> serializer;
public MyIHideableJsonSerializer(JsonSerializer<IHideable> serializer) {
this.serializer = serializer;
}
@Override
public void serialize(IHideable value,
JsonGenerator jgen,
SerializerProvider provider) throws IOException {
if (!value.isHidden()) {
serializer.serialize(value, jgen, provider);
}
}
}
}
public static void main(String[] args) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.setSerializerModifier(new MyBeanSerializerModifier());
mapper.registerModule(module);
PersonalInfo p1 = new PersonalInfo("John", 30, false);
PersonalInfo p2 = new PersonalInfo("Ivan", 20, true);
Address a1 = new Address("A", "B", false);
Address a2 = new Address("C", "D", true);
System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString
(Arrays.asList(p1, p2, a1, a2)));
}
}
Output:
[ {
"name" : "John",
"age" : 30
}, {
"city" : "A",
"street" : "B"
} ]
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