Jackson custom deserializer 2018-12-07 01:43
We can use Jackson convert between json and object. But sometimes we need custom deserializer for special json. Let's say you need to handle the json like following.
{
"name": "henryxi",
"age": 30,
"address": "Beijing,Los Angeles"
}
There are two addresses in address node. We can custom deserializer to convert this json to the object like following.
public class User {
public User(String name, int age, List<Address> address) {
this.name = name;
this.age = age;
this.address = address;
}
private String name;
private int age;
private List<Address> address;
//getter and setter
}
The complete code is here.
public class CustomDeserializer extends StdDeserializer<User> {
public CustomDeserializer() {
super(User.class);
}
public CustomDeserializer(Class<?> vc) {
super(vc);
}
public CustomDeserializer(JavaType valueType) {
super(valueType);
}
public CustomDeserializer(StdDeserializer<?> src) {
super(src);
}
@Override
public User deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
JsonNode node = jp.getCodec().readTree(jp);
int age = (Integer) node.get("age").numberValue();
String name = node.get("name").asText();
String addressStr = node.get("address").asText();
List<Address> addressList = new LinkedList<>();
for (String address : addressStr.split(",")) {
addressList.add(new Address(address));
}
return new User(name, age, addressList);
}
}
// you need to add this annotation to tell Jackson to use this deserializer
@JsonDeserialize(using = CustomDeserializer.class)
public class User {
public User(String name, int age, List<Address> address) {
this.name = name;
this.age = age;
this.address = address;
}
private String name;
private int age;
private List<Address> address;
//getter, setter and toString method
}
public class Address {
private String value;
//getter, setter and toString method
}
public class ConverterClient {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper();
String json = "{ \"name\": \"henryxi\", \"age\": 30, \"address\": \"Beijing,Los Angeles\" } ";
User user = objectMapper.readValue(json, User.class);
System.out.println(user);
}
}
The output is here.
User{name='henryxi', age=30, address=[Address{value='Beijing'}, Address{value='Los Angeles'}]}
SUMMARY
For most json we can defined beans and use Jackson to deserialize them. If you want deserialize them in custom way you can use @JsonDeserialize to specify a custom deserializer. You need extends StdDeserializer class and implement deserialize method.
EOF