Assuming I have the following JSON:
{
"property": "123:1234"
}
How do I use Jackson annotations to ensure that the string value of "property" is de-serialized to a self-defined class rather than a String object?
I went through their documentation and I was unable to find this particular feature.
Thanks in advance.
You could create custom deserializer for your field. Assuming you want to map it to SomeClass object :
public class SomeClass {
#JsonDeserialize(using = CustomPropertyDeserializer.class)
private Properties property;
public Properties getProperty() {
return property;
}
public void setProperty(Properties property) {
this.property = property;
}
}
You annotate your field that you want to deserialize customly with #JsonDeserialize annotation passing custom deserializer.
Your deserializer could look like this :
public class CustomPropertyDeserializer extends StdDeserializer<Properties> {
public CustomPropertyDeserializer() {
super(Properties.class);
}
#Override
public Properties deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
String valueAsString = p.getValueAsString();
String[] split = valueAsString.split(":");
return new Properties(split[0], split[1]);
}
}
And custom property class :
public class Properties {
private String first;
private String second;
public Properties(String first, String second) {
this.first = first;
this.second = second;
}
public String getFirst() {
return first;
}
public void setFirst(String first) {
this.first = first;
}
public String getSecond() {
return second;
}
public void setSecond(String second) {
this.second = second;
}
}
For testing it :
public static void main(String[] args) throws IOException {
String s = Files.lines(Paths.get("src/main/resources/data.json")).collect(Collectors.joining());
ObjectMapper objectMapper = new ObjectMapper();
SomeClass someClass = objectMapper.readValue(s, SomeClass.class);
System.out.println(someClass.getProperty().getFirst());
System.out.println(someClass.getProperty().getSecond());
}
The output is then :
123
1234
So all the custom logic how to map your String to some class that you define could be placed in deserialize method of your custom deserializer.
First thing first define your class that needs to be used:
#JsonInclude(JsonInclude.Include.NON_NULL)
public class JsonTest{
#JsonProperty("property")
private String property;
//define your getters and setters for the field
Then you can use the ObjectMapper class from jackson:
public static <T> T extractObjectFromJson(String jsonText, Class<T> type) {
try {
return new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false).reader().forType(type)
.readValue(jsonText);
} catch (Exception e) {
//Manage your exception here
}
return null;
}
So you can just call the method extractobjectFromJson(//Your JSON String, JsonTest.class) to get your JSON deserialized.
Related
I want to convert a json into Java class by having custom deserializer.
I'm able to serialize ACC_NUM, NAME and any other fields from json but not sure what can be done to convert MOBILE_NUMBER_1,MOBILE_NUMBER_2 like fields into single JSONArray(See AccountInfo class). There can be many more fields like this and count also is not fixed. Example there can be ADDRESS_1, ADDRESS_2 till ADDRESS_20 and so on and all this fields should go in JSONArray of ADDRESS after deserilization.
I have a Map of Map which holds info like this:
{
"accountInfo": {
"ACC_NUM": "1234567890",
"NAME": "John Cena",
"MOBILE_NUMBER_1": "12376534",
"MOBILE_NUMBER_2": "12376534",
"MOBILE_NUMBER_3": "12376534",
"MOBILE_NUMBER_4": "12376534"
},
"someOther": {
//similer to above
}
}
This info I want to convert to the following class CommonInfo:
public class CommonInfo {
private AccountInfo accountInfo;
//other properties...
}
#JsonIgnoreProperties(ignoreUnknown = true)
public class AccountInfo {
#JsonProperty("ACC_NUM")
private FieldValue<BigInteger> accountNum;
#JsonProperty("NAME")
private FieldValue<String> name;
#JsonProperty("MOBILE_NUMBER")
private FieldValue<JSONArray> mobileNumber;
}
//FieldValue class
public interface FieldValue<T> {
T getInitialValue();
void setInitialValue(T initialValue);
T getValue();
void setValue(T value);
}
#JsonInclude(JsonInclude.Include.ALWAYS)
public class FieldValueImpl<T> implements FieldValue<T> {
protected T initialValue;
protected T value;
//getters, setters, cons..
}
My service code takes json/Map and tries to convert it to CommonInfo class
#Service
public class MyService {
private final ObjectMapper jsonMapper = new ObjectMapper();
#PostConstruct
protected void init() {
SimpleModule simpleModule = new SimpleModule();
simpleModule.addSerializer(FieldValue.class, new FieldValueSerializer());
simpleModule.addDeserializer(FieldValue.class, new FieldValueDeserializer());
jsonMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);
jsonMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
jsonMapper.registerModule(simpleModule);
}
public CommonInfo setPojoResult(Map<String, LinkedHashMap<String, String>> contentAsMap) {
return jsonMapper.convertValue(contentAsMap, CommonInfo.class);
}
}
Serializer and Deserializer looks like this:
public class FieldValueDeserializer extends JsonDeserializer<FieldValue<?>> implements ContextualDeserializer {
private JavaType valueType;
public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property)
throws JsonMappingException {
var deserializer = new FieldValueDeserializer();
if (property == null) {
deserializer.valueType = ctxt.getContextualType().containedType(0);
} else {
var wrapperType = property.getType();
var valueType = wrapperType.containedType(0);
deserializer.valueType = valueType;
}
return deserializer;
}
#Override
public FieldValue<?> deserialize(JsonParser parser, DeserializationContext context) throws IOException {
FieldValueDeserializer deserializer = new FieldValueDeserializer();
deserializer.getKnownPropertyNames();
FieldValue<?> fieldValueImpl = new FieldValueImpl<>();
if (valueType.toString().contains("java.time.LocalDate")) {
JsonNode node = parser.getCodec().readTree(parser);
FieldValue<LocalDate> f1 = new FieldValueImpl<>();
f1.setValue(DateUtils.convertJulianToLocalDate(node.textValue()));
return f1;
} else {
fieldValueImpl.setValue(context.readValue(parser, valueType));
}
return fieldValueImpl;
}
}
//--
public class FieldValueSerializer extends StdSerializer<FieldValue> {
public FieldValueSerializer() {
this(null);
}
public FieldValueSerializer(Class<FieldValue> vc) {
super(vc);
}
#Override
public void serialize(FieldValue value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
jgen.writeString(String.valueOf(value.getCurValue()));
}
}
Context
Say you have:
public class Dto {
private String name;
private String List<Custom> customs;
// getters and setters...
}
and
public class Custom {
private String something;
private String else;
// getters and setters...
}
Your Spring MVC RestController receives a list of Dto:
#PostMapping
public String create(#RequestBody #Valid List<Dto> dtos) {
return myService.process(features);
}
Input
However, you know that the client-side service which will send data to your controller will send something like this:
[
{
"name": "Bob",
"customs": [
"{\n \"something\": \"yes\",\n \"else\": \"no\"\n }"
]
}
]
Notice how the List<Custom> actually ends up being received as a List<String>. Please assume this cannot be changed on the client-side and we have to deal with it on the server-side.
Question
Is there a Jackson annotation which would automagically take the input String and try to serialize it into a Custom class?
Attempts
A few things that didn't work, including:
#JsonSerialize(using = ToStringSerializer.class)
private List<Custom> customs;
along with
public Custom(String json) {
try {
new ObjectMapper().readerFor(Custom.class).readValue(json);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
As it is, we have had to change the customs type to List<String> and add a utility method which converts a String into a Custom using an ObjectMapper. This is rather dissatisfying.
You need to implement custom deserialiser or converter which would be used to convert given payload to required type. One trick, you could use is to create new ObjectMapper and use it for internal deserialisation.
Example usage:
class CustomConverter extends StdConverter<String, Custom> {
private final ObjectMapper mapper = new ObjectMapper();
#Override
public Custom convert(String value) {
try {
return mapper.readValue(value, Custom.class);
} catch (JsonProcessingException e) {
throw new IllegalArgumentException(value);
}
}
}
class Dto {
private String name;
#JsonDeserialize(contentConverter = CustomConverter.class)
private List<Custom> customs;
}
You need to create a custom Deserializer.
public class CustomDeserializer extends StdDeserializer<Custom> {
public CustomDeserializer() {
this(null);
}
public CustomDeserializer(Class<?> vc) {
super(vc);
}
#Override
public Custom deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
JsonNode node = jp.getCodec().readTree(jp);
int id = (Integer) ((IntNode) node.get("id")).numberValue();
String name = node.get("name").asText();
...
return new Custom(id, name, ...);
}
}
and register the deserializer on the Custom class:
#JsonDeserialize(using = CustomDeserializer.class)
public class Custom {
...
}
I need deserialize JSON to class depends on type of one of the property.
I have the following JSON:
{
"type":"text",
"message": "Hello"
}
and I have the following Enum:
public enum MyEnumType {
TEXT("text"),
DATE("date")
private final String type;
MyEnumType(String type) {
this.type = type;
}
}
and I have the Abstract class shown as the following:
public abstract class MyClass {
public MyEnumType type;
}
and I have some of classes which extends MyClass
public class TextMessage extends MyClass {
public String message;
}
public class DateMessage extends MyClass {
...
}
and I need to write some code looks like the following:
ObjectMapper mapper = new ObjectMapper();
MyClass instance = mapper.readValue(json, MyClass.class);
and have to get instance depends on type property, if type is TEXT to deserialize to TextMessage class otherwise to DateMessage class.
How can I do this? Can you give me some ideas or examples?
You approach is a little bit confuse but maybe you could do something similar to this:
public class Test {
public static void main(String[] args) throws JsonParseException, JsonMappingException, IOException {
String json = "{\"type\":\"text\", \"message\": \"Hello\"}";
// create ObjectMapper instance
ObjectMapper objectMapper = new ObjectMapper();
MainObj mo = objectMapper.readValue(json, MainObj.class);
System.out.println("type: " + mo.getType());
MyClass instance = null;
if (mo.getType().equalsIgnoreCase("text")) {
// Do it for the 'text'
} else {
// Do it for the 'date'
}
}
}
class MainObj {
private String type = "";
private Object message = null;
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public Object getMessage() {
return message;
}
public void setMessage(Object message) {
this.message = message;
}
}
class MyClass {
public MyClass() {
}
}
I want to use Jackson JSON to serialize/deserialize a class containing an enum object. My class is:
class Bar {
#JsonProperty("rateType")
#JsonDeserialize(using = ReturnedRateTypeDeserializer.class)
private ReturnedRateType rateType;
public ReturnedRateType getRateType() {
return rateType;
}
public void setRateType(ReturnedRateType rateType) {
this.rateType = rateType;
}
}
The enum class ReturnedRateType is defined as:
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
public enum ReturnedRateType {
AA("AA"),
BB("BB"),
CC("CC");
#JsonProperty("value")
private String value;
ReturnedRateType(String value) {
this.value = value;
}
#JsonCreator
public static ReturnedRateType fromValue(final String value) {
if (value != null) {
for (ReturnedRateType type : ReturnedRateType.values()) {
if (value.equalsIgnoreCase(type.value)) {
return type;
}
}
}
return null;
}
}
As you see, I added #JsonFormat annotation to tell Jackson to serialize this enum as POJO, and added #JsonCreator annotation to get a static factory method from given string to enum object. Since Jackson can only serialize but can't deserialize from object representation to enum, I added the following customized deserializer for the enum ReturnedRateType:
public class ReturnedRateTypeDeserializer extends JsonDeserializer<ReturnedRateType> {
#Override
public ReturnedRateType deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
ReturnedRateType type = ReturnedRateType.fromValue(jp.getValueAsString());
if(type != null)
return type;
throw new JsonMappingException("invalid value for ReturnedRateType");
}
}
But when I tested deserialization from a JSON string to enum, I got the error. The JSON string is:
{"rateType": {"value": "AA"}}
My test code is:
#Test
public void RateTypeToEnum() {
String json = "{\"rateType\": {\"value\": \"AA\"}}";
System.out.println(json);
ObjectMapper mapper = new ObjectMapper();
Bar bar = null;
try {
bar = mapper.readValue(json, Bar.class);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(bar.getRateType());
}
I expect to see the output should be AA. But jp.getValueAsString() in my customized deserializer ReturnedRateTypeDeserializer is null during the execution:
ReturnedRateType type = ReturnedRateType.fromValue(jp.getValueAsString()); //jp.getValueAsString() is null here!
Thus it returns error. So what is wrong here?
According to the Jackson 2.5.X documentation on the JsonFormat annotation the Shape.Object does not work for the enum deserialisation:
Enums: Shapes JsonFormat.Shape.STRING and JsonFormat.Shape.NUMBER can
be used to change between numeric (index) and textual (name or
toString()); but it is also possible to use JsonFormat.Shape.OBJECT
to serialize (but not deserialize).
I'd make the JsonCreator static method accept a JsonNode and read the string value from it.
Note that this would work since 2.5.X. In early versions you would need to write a custom deserialiser. Here is an example:
public class JacksonEnumObjectShape {
#JsonFormat(shape = JsonFormat.Shape.OBJECT)
#JsonDeserialize(using = ReturnedRateTypeDeserializer.class)
public enum ReturnedRateType {
AA("AA"),
BB("BB"),
CC("CC");
#JsonProperty("value")
private String value;
ReturnedRateType(String value) {
this.value = value;
}
#JsonCreator
public static ReturnedRateType fromValue(final JsonNode jsonNode) {
for (ReturnedRateType type : ReturnedRateType.values()) {
if (type.value.equals(jsonNode.get("value").asText())) {
return type;
}
}
return null;
}
}
// can be avoided since 2.5
public static class ReturnedRateTypeDeserializer extends JsonDeserializer<ReturnedRateType> {
#Override
public ReturnedRateType deserialize(
final JsonParser jp,
final DeserializationContext ctxt) throws IOException {
final JsonNode jsonNode = jp.readValueAsTree();
return ReturnedRateType.fromValue(jsonNode);
}
}
public static void main(String[] args) throws IOException {
final ObjectMapper mapper = new ObjectMapper();
final String json = mapper.writeValueAsString(ReturnedRateType.AA);
System.out.println(json);
System.out.println(mapper.readValue(json, ReturnedRateType.class));
}
}
Output:
{"value":"AA"}
AA
I have this POJO :
public class JsonObj {
private String id;
private List<Location> location;
public String getId() {
return id;
}
public List<Location> getLocation() {
return location;
}
#JsonSetter("location")
public void setLocation(){
List<Location> list = new ArrayList<Location>();
if(location instanceof Location){
list.add((Location) location);
location = list;
}
}
}
the "location" object from the json input can be either a simple instance of Location or an Array of Location. When it is just one instance, I get this error :
Could not read JSON: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
I've tried to implement a custom setter but it didn't work. How could I do to map either a Location or a List depending on the json input?
Update: Mher Sarkissian's soulution works fine, it can also be used with annotations as suggested here, like so:.
#JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY)
private List<Item> item;
My deepest sympathies for this most annoying problem, I had just the same problem and found the solution here: https://stackoverflow.com/a/22956168/1020871
With a little modification I come up with this, first the generic class:
public abstract class OptionalArrayDeserializer<T> extends JsonDeserializer<List<T>> {
private final Class<T> clazz;
public OptionalArrayDeserializer(Class<T> clazz) {
this.clazz = clazz;
}
#Override
public List<T> deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException {
ObjectCodec oc = jp.getCodec();
JsonNode node = oc.readTree(jp);
ArrayList<T> list = new ArrayList<>();
if (node.isArray()) {
for (JsonNode elementNode : node) {
list.add(oc.treeToValue(elementNode, clazz));
}
} else {
list.add(oc.treeToValue(node, clazz));
}
return list;
}
}
And then the property and the actual deserializer class (Java generics is not always pretty):
#JsonDeserialize(using = ItemListDeserializer.class)
private List<Item> item;
public static class ItemListDeserializer extends OptionalArrayDeserializer<Item> {
protected ItemListDeserializer() {
super(Item.class);
}
}
This is already supported by jackson
objectMapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true);