With Jackson, it's easy to disable all annotations for a given ObjectMapper.
Is there a way to only disable one given annotation?
// disable all
ObjectMapper mapper = new ObjectMapper()
mapper.disable(MapperFeature.USE_ANNOTATIONS);
// disable one?
ObjectMapper mapper = new ObjectMapper()
mapper.disable(#JsonIgnore);
Using #JacksonAnnotationsInside, I've defined a custom Jackson annotation and I only want it to be used in certain circumstances.
This the best I've come across. I think I saw it on the Jackson user group forums somewhere.
Essentially it makes a custom annotation introspector, which returns null if it sees that it has a specific annotation (in this case JsonTypeInfo)
JacksonAnnotationIntrospector ignoreJsonTypeInfoIntrospector = new JacksonAnnotationIntrospector() {
#Override
protected TypeResolverBuilder<?> _findTypeResolver(
MapperConfig<?> config, Annotated ann, JavaType baseType) {
if (!ann.hasAnnotation(JsonTypeInfo.class)) {
return super._findTypeResolver(config, ann, baseType);
}
return null;
}
};
mapper.setAnnotationIntrospector(ignoreJsonTypeInfoIntrospector);
I think it's a better idea to override findPropertiesToIgnore method like this:
JacksonAnnotationIntrospector ignoreJsonTypeInfoIntrospector = new JacksonAnnotationIntrospector() {
#Override
public String[] findPropertiesToIgnore(AnnotatedClass ac) {
ArrayList<String> ret = new ArrayList<String>();
for (Method m : ac.getRawType().getMethods()) {
if(ReflectionUtils.isGetter(m)){
if(m.getAnnotation(Transient.class) != null)
ret.add(ReflectionUtils.getPropertyName(m));
}
};
return ret.toArray(new String[]{});
}
};
objectMapper = new ObjectMapper();
objectMapper.setAnnotationIntrospector(ignoreJsonTypeInfoIntrospector);
This solution worked for me. Check this for more info
private static final JacksonAnnotationIntrospector IGNORE_ENUM_ALIAS_ANNOTATIONS = new JacksonAnnotationIntrospector() {
#Override
protected <A extends Annotation> A _findAnnotation(final Annotated annotated, final Class<A> annoClass) {
if (!annotated.hasAnnotation(JsonEnumAliasSerializer.class)) {
return super._findAnnotation(annotated, annoClass);
}
return null;
}
};
And my custom annotation:
#Retention(RetentionPolicy.RUNTIME)
#JacksonAnnotationsInside
#JsonSerialize(using = JsonEnumSerializer.class)
public #interface JsonEnumAliasSerializer {
}
And ObjectMapper:
final ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setAnnotationIntrospector(IGNORE_ENUM_ALIAS_ANNOTATIONS);
Here is a simpler way (August 2022) to do it in Kotlin (you can translate to Java if you really want to):
(I use this in a Ktor/KMongo project to prevent Transient attributes from being persisted because KMongo requires #JsonIgnore, which then also prevents my other mappers from serializing those properties!)
#Target(PROPERTY_GETTER)
annotation class Transient
private val TransientIntrospector: JacksonAnnotationIntrospector = object : JacksonAnnotationIntrospector() {
override fun hasIgnoreMarker(m: AnnotatedMember): Boolean =
m.allAnnotations.has(Transient::class.java) || super.hasIgnoreMarker(m)
}
private class IgnoreTransientModule : SimpleModule() {
override fun setupModule(context: SetupContext) {
super.setupModule(context)
context.appendAnnotationIntrospector(TransientIntrospector)
}
}
// Just register the module in your `ObjectMapper` instance:
val ignoreTransientMapper = with(ObjectMapper()) {
registerModule(IgnoreTransientModule())
}
// And here is how to use it:
data class Customer(
val id: String? = null,
val firstName: String,
val lastName: String,
) {
#get:Transient
val fullName: String
get() = "$firstName $lastName"
}
Related
I have the following system:
I am sending MediaType.APPLICATION_JSON_VALUEs from spring controllers to my client and vice versa.
I also have an export/import feature of my to-be-serialized classes. The JSON File is created by using an ObjectMapper and utilizing the writeValueAsString and readValue methods. I am reading from and writing into the json file.
Both of those serialization paths currently utilize the same serializers/deserializers.
I use the #JsonSerialize and #JsonDeserialize annotations to define custom serialization for some of my objects.
I want to serialize those objects differently for export/import.
So I want to swap the serializer / deserializer for the export/import task. Something like this:
If I understand the docs correctly, those two annotations only allow one using class. But I want to register multiple serializers/deserializers and use them based on some conditional logic.
You might want to have two separate ObjectMapper instances configured for Server and Client.
Server module:
ObjectMapper serverMapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(ServerDTO.class, new CustomerFileSerializer());
module.addDeserializer(ServerDTO.class, new CustomerFileDeserializer());
serverMapper.registerModule(module);
ServerDTO serverDto = serverMapper.readValue(jsonInput, ServerDTO.class);
String serialized = serverMapper.writeValueAsString(serverDto);
and
Client module:
ObjectMapper clientMapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(ClientDTO.class, new CustomerClientSerializer());
module.addDeserializer(ClientDTO.class, new CustomerClientDeserializer());
clientMapper.registerModule(module);
ClientDTO clientDTO = clientMapper.readValue(jsonInput, ClientDTO.class);
String serialized = clientMapper.writeValueAsString(clientDTO);
So I was trying to figure this out for the last few days. This is the progress I made so far:
I did two overrides for the default ObjectMapper in Spring and made sure they are configured like the default.
My custom mappers look like this:
#Configuration
public class JacksonConfig {
#Bean
#Primary
public ObjectMapper defaultV7ObjectMapper() {
ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule())
.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false)
.configure(SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS, false);
// emulate the default settings as described here: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-customize-the-jackson-objectmapper
objectMapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);
objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
SimpleModule module = new SimpleModule();
module.addSerializer(Customer.class, new CustomerClientSerializer());
module.addDeserializer(Customer.class, new CustomerClientDeserializer());
objectMapper.registerModule(module);
return objectMapper;
}
#Bean("exportImportMapper")
public ObjectMapper exportImportMapper() {
ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule())
.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false)
.configure(SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS, false);
// emulate the default settings as described here: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-customize-the-jackson-objectmapper
objectMapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);
objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
SimpleModule module = new SimpleModule();
module.addSerializer(Customer.class, new CustomerFileSerializer());
module.addDeserializer(Customer.class, new CustomerFileDeserializer());
objectMapper.registerModule(module);
return objectMapper;
}
}
I also removed the #JsonSerialize and #JsonDeserialize annotations from my entities.
HOWEVER there is one big difference with this change from annotations to adding the serializers via the module.
Let's say I have a class A that has a Customer property with the #JsonSerialize and #JsonDeserialize annotation.
Let's also say I have a class B that has a Customer property without annotations.
By removing the annotations and setting the serializer/deserializer as shown above I have now added theses serializers/deserializers to both Customer properties. So it's not equivalent.
Or am I missing something here?
This is my solution
It's not pretty but does its job.
I left my old jackson config untouched, so the client<->server serialization stays the same.
I then added this custom ObjectMapper to take care of my server<->file.
My custom ObjectMapper does the following things:
It registers a new custom JacksonAnnotationIntrospector, which I configured to ignore certain annotations. I also configured it to use my selfmade annotation #TransferJsonTypeInfo whenever a property has both the #TransferJsonTypeInfo as well as the #JsonTypeInfo annotation.
I registered my CustomerFileSerializer and CustomerFileDeserializer for this ObjectMapper.
#Service
public class ImportExportMapper {
protected final ObjectMapper customObjectMapper;
private static final JacksonAnnotationIntrospector IGNORE_JSON_ANNOTATIONS_AND_USE_TRANSFERJSONTYPEINFO = BuildImportExportJacksonAnnotationIntrospector();
public ImportExportMapper(){
customObjectMapper = new ObjectMapper().registerModule(new JavaTimeModule())
.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false)
.configure(SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS, false);
// emulate the default settings as described here: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto-customize-the-jackson-objectmapper
customObjectMapper.disable(MapperFeature.DEFAULT_VIEW_INCLUSION);
customObjectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
SimpleModule module = new SimpleModule();
module.addSerializer(Customer.class, new CustomerFileSerializer());
module.addDeserializer(Customer.class, new CustomerFileDeserializer());
customObjectMapper.setAnnotationIntrospector(IGNORE_JSON_ANNOTATIONS_AND_USE_TRANSFERJSONTYPEINFO);
customObjectMapper.registerModule(module);
}
public String writeValueAsString(Object data) {
try {
return customObjectMapper.writeValueAsString(data);
} catch (JsonProcessingException e) {
e.printStackTrace();
throw new IllegalArgumentException();
}
}
public ObjectTransferData readValue(String fileContent, Class clazz) throws JsonProcessingException {
return customObjectMapper.readValue(fileContent, clazz);
}
private static JacksonAnnotationIntrospector BuildImportExportJacksonAnnotationIntrospector() {
return new JacksonAnnotationIntrospector() {
#Override
protected <A extends Annotation> A _findAnnotation(final Annotated annotated, final Class<A> annoClass) {
if (annoClass == JsonTypeInfo.class && _hasAnnotation(annotated, FileJsonTypeInfo.class)) {
FileJsonTypeInfo fileJsonTypeInfo = _findAnnotation(annotated, TransferJsonTypeInfo.class);
if(fileJsonTypeInfo != null && fileJsonTypeInfo.jsonTypeInfo() != null) {
return (A) fileJsonTypeInfo.jsonTypeInfo(); // this cast should be safe because we have checked the annotation class
}
}
if (ignoreJsonAnnotations(annoClass)) return null;
return super._findAnnotation(annotated, annoClass);
}
};
}
private static <A extends Annotation> boolean ignoreJsonAnnotations(Class<A> annoClass) {
if (annoClass == JsonSerialize.class) {
return true;
}
if(annoClass == JsonDeserialize.class){
return true;
}
if(annoClass == JsonIdentityReference.class){
return true;
}
return annoClass == JsonIdentityInfo.class;
}
}
My custom annotation is defined and described like this:
/**
* This annotation inside of a annotation solution is a way to tell the importExportMapper how to serialize/deserialize
* objects that already have a wrongly defined #JsonTypeInfo annotation (wrongly defined for the importExportMapper).
*
* Idea is taken from here: https://stackoverflow.com/questions/58495480/how-to-properly-override-jacksonannotationintrospector-findannotation-to-replac
*/
#Target(ElementType.FIELD)
#Retention(RetentionPolicy.RUNTIME)
public #interface FileJsonTypeInfo {
JsonTypeInfo jsonTypeInfo();
}
And it is used like this:
#JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
#JsonTypeInfo(defaultImpl = Customer.class, property = "", use = JsonTypeInfo.Id.NONE)
#TransferJsonTypeInfo(jsonTypeInfo = #JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "customeridentifier"))
#JsonIdentityReference(alwaysAsId = true)
#JsonDeserialize(using = CustomerClientDeserializer.class)
#JsonSerialize(using = CustomerClientSerializer.class)
private Customer customer;
I'm trying to determine how to print out a JSON that looks like this, using Java's Jackson library:
{
"status": {
{
"busStatus" : {
"status" : null,
"transactions" : "0",
"retries" : "0",
"failures" : "0"
}
}
}
}
I'm 95% there, but the outermost object is not currently being printed. This is what I'm currently getting outputted:
{
"busStatus" : {
"status" : null,
"transactions" : "0",
"retries" : "0",
"failures" : "0"
}
}
I have a Java class that looks like this:
public class DataClass {
public StatusData status = new StatusData();
public StatusConfig config = new StatusConfig();
public class StatusData {
public SerialStatus busStatus = new SerialStatus();
}
public class StatusConfig {
}
public class SerialStatus {
public String status = null;
public String transactions = "0";
public String retries = "0";
public String failures = "0";
}
}
I'm printing this class to json using the code below:
private DataClass internalData;
ObjectMapper mapper = new ObjectMapper();
status = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(internalData.status);
Is there a way I can configure Jackson to print out the name of the object its serializing into the JSON?
To achieve what you want, you need to print DataClass instead of StatusData. Something like below:
private DataClass internalData = <initialize>;
ObjectMapper mapper = new ObjectMapper();
String data =
mapper.writerWithDefaultPrettyPrinter().writeValueAsString(internalData);
You can use Jackson Filter to control the serialization process, I think it should work with your use case, at least one way to do it.
Use the filter annotation and then create two different filters for your class, where you can define which field to skip, and use it with the ObjectMapper accordingly to convert the whole internalData object, so when you need to skip the status, use one filter and when you need to skip the config associate the other filter with the mapper, while always serializing the parent object. Which should give you the structure you want.
#JsonFilter("filter_serializer")
class User {
public String v1;
public String v2;
}
String[] fieldsToSkip = new String[] { "v1" };
ObjectMapper mapper = new ObjectMapper();
final SimpleFilterProvider filter = new SimpleFilterProvider();
filter.addFilter("filter_serializer",
SimpleBeanPropertyFilter.serializeAllExcept(fieldsToSkip));
User dtoObject = new User();
dtoObject.v1 = "v1";
dtoObject.v2 = "v2";
String jsonStr = mapper.writer(filter).writeValueAsString(dtoObject);
I was able to find the solution I was looking for, from this website.
I've gotten rid of the DataClass and now only have a StatusData and a StatusConfig class. I've included how the StatusData class would look below:
#JsonRootName(value = "status")
public class StatusData {
String status;
String transactions;
// so on
}
To parse the class, I needed to add the JsonRootName annotation above, and also enable a feature on the mapper, as below:
private DataClass internalData;
ObjectMapper mapper = new ObjectMapper();
mapper.enable(SerializationFeature.WRAP_ROOT_VALUE); // don't forget this!
statusText = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(statusObject);
Separately, if you'd like to deserialize a JSON like the one I had into a class like StatusData, do this:
mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true);
statusObject = mapper.readValue(statusText, StatusData.class);
With this data model...
TestClass.kt
data class TestClass (val bar: Optional<Double>?)
My goal is to deserialize the following json values as such:
{"foo": 3.5} --> foo = 3.5
{"foo": null} --> foo = Optional.empty() // This is currently my problem. foo is null and I can't seem to fix it
{} --> foo = null
I've seen the solution here and tried this, but the breakpoints in my "deserialize" method never seem to hit.
OptionalDeserializer.java
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
import java.io.IOException;
import java.util.Optional;
public class OptionalDeserializer extends JsonDeserializer<Optional<?>> implements ContextualDeserializer {
private JavaType valueType;
#Override
public JsonDeserializer<?> createContextual(DeserializationContext context, BeanProperty property) {
this.valueType = property.getType().containedType(0);
return this;
}
#Override
public Optional<?> deserialize(final JsonParser parser, final DeserializationContext context) throws IOException {
final JsonNode node = parser.getCodec().readTree(parser);
return node.isNull()
? Optional.empty()
: Optional.of(context.readValue(parser, valueType));
}
}
TestDeserialization.kt
fun main(): {
val objectMapper = ObjectMapper().registerModule(KotlinModule())
val module = SimpleModule()
module.addDeserializer(Optional::class.java, OptionalDeserializer())
objectMapper.registerModule(module)
objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL)
objectMapper.configure(JsonGenerator.Feature.WRITE_BIGDECIMAL_AS_PLAIN, true)
objectMapper.configure(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS, true)
objectMapper.nodeFactory = JsonNodeFactory.withExactBigDecimals(true)
val inputJson = """{"foo" : null}"""
val expectedObject = TestClass(foo = Optional.empty())
val actualObject = objectMapper.readValue(inputJson, TestClassBravo::class.java)
assertEquals(expectedObject, actualObject)
}
build.gradle (for version info)
compile 'com.fasterxml.jackson.core:jackson-databind:2.9.8'
compile 'com.fasterxml.jackson.module:jackson-module-kotlin:2.9.8'
There are two ways you can handle this.
It would be easier not to use a custom serializer, but rely on the jackson default Jdk8Module (see here)
If you want your custom Deserializer, you need to specify the null access pattern, else the deserializer will not be called for null values:
Code for 2:
// In OptionalDeserializer
#Override
public AccessPattern getNullAccessPattern() {
return AccessPattern.CONSTANT;
}
I was trying to filter out certain fields from serialization via SimpleBeanPropertyFilter using the following (simplified) code:
public static void main(String[] args) {
ObjectMapper mapper = new ObjectMapper();
SimpleFilterProvider filterProvider = new SimpleFilterProvider().addFilter("test",
SimpleBeanPropertyFilter.filterOutAllExcept("data1"));
try {
String json = mapper.writer(filterProvider).writeValueAsString(new Data());
System.out.println(json); // output: {"data1":"value1","data2":"value2"}
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
private static class Data {
public String data1 = "value1";
public String data2 = "value2";
}
Us I use SimpleBeanPropertyFilter.filterOutAllExcept("data1")); I was expecting that the created serialized Json string contains only {"data1":"value1"}, however I get {"data1":"value1","data2":"value2"}.
How to create a temporary writer that respects the specified filter (the ObjectMapper can not be re-configured in my case).
Note: Because of the usage scenario in my application I can only accept answers that do not use Jackson annotations.
If for some reason MixIns does not suit you. You can try this approach:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.setAnnotationIntrospector(new JacksonAnnotationIntrospector(){
#Override
public boolean hasIgnoreMarker(final AnnotatedMember m) {
List<String> exclusions = Arrays.asList("field1", "field2");
return exclusions.contains(m.getName())|| super.hasIgnoreMarker(m);
}
});
You would normally annotate your Data class to have the filter applied:
#JsonFilter("test")
class Data {
You have specified that you can't use annotations on the class. You could use mix-ins to avoid annotating Data class.
#JsonFilter("test")
class DataMixIn {}
Mixins have to be specified on an ObjectMapper and you specify you don't want to reconfigure that. In such a case, you can always copy the ObjectMapper with its configuration and then modify the configuration of the copy. That will not affect the original ObjectMapper used elsewhere in your code. E.g.
ObjectMapper myMapper = mapper.copy();
myMapper.addMixIn(Data.class, DataMixIn.class);
And then write with the new ObjectMapper
String json = myMapper.writer(filterProvider).writeValueAsString(new Data());
System.out.println(json); // output: {"data1":"value1"}
The example of excluding properties by name:
public Class User {
private String name = "abc";
private Integer age = 1;
//getters
}
#JsonFilter("dynamicFilter")
public class DynamicMixIn {
}
User user = new User();
String[] propertiesToExclude = {"name"};
ObjectMapper mapper = new ObjectMapper()
.addMixIn(Object.class, DynamicMixIn.class);
FilterProvider filterProvider = new SimpleFilterProvider()
.addFilter("dynamicFilter", SimpleBeanPropertyFilter.filterOutAllExcept(propertiesToExclude));
mapper.setFilterProvider(filterProvider);
mapper.writeValueAsString(user); // {"name":"abc"}
You can instead of DynamicMixIn create MixInByPropName
#JsonIgnoreProperties(value = {"age"})
public class MixInByPropName {
}
ObjectMapper mapper = new ObjectMapper()
.addMixIn(Object.class, MixInByPropName.class);
mapper.writeValueAsString(user); // {"name":"abc"}
Note: If you want exclude property only for User you can change parameter Object.class of method addMixIn to User.class
Excluding properties by type you can create MixInByType
#JsonIgnoreType
public class MixInByType {
}
ObjectMapper mapper = new ObjectMapper()
.addMixIn(Integer.class, MixInByType.class);
mapper.writeValueAsString(user); // {"name":"abc"}
It seems you have to add an annotation which indicts which filter to use when doing the serialization to the bean class if you want the filter to work:
#JsonFilter("test")
public class Data {
public String data1 = "value1";
public String data2 = "value2";
}
EDIT
The OP has just added a note that just take the answer that not using a bean animation, then if the field you want to export is very less amount, you can just retrieve that data and build a Map of List yourself, there seems no other way to do that.
Map<String, Object> map = new HashMap<String, Object>();
map.put("data1", obj.getData1());
...
// do the serilization on the map object just created.
If you want to exclude specific field and kept the most field, maybe you could do that with reflect. Following is a method I have written to transfer a bean to a map you could change the code to meet your own needs:
protected Map<String, Object> transBean2Map(Object beanObj){
if(beanObj == null){
return null;
}
Map<String, Object> map = new HashMap<String, Object>();
try {
BeanInfo beanInfo = Introspector.getBeanInfo(beanObj.getClass());
PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
for (PropertyDescriptor property : propertyDescriptors) {
String key = property.getName();
if (!key.equals("class")
&& !key.endsWith("Entity")
&& !key.endsWith("Entities")
&& !key.endsWith("LazyInitializer")
&& !key.equals("handler")) {
Method getter = property.getReadMethod();
if(key.endsWith("List")){
Annotation[] annotations = getter.getAnnotations();
for(Annotation annotation : annotations){
if(annotation instanceof javax.persistence.OneToMany){
if(((javax.persistence.OneToMany)annotation).fetch().equals(FetchType.EAGER)){
List entityList = (List) getter.invoke(beanObj);
List<Map<String, Object>> dataList = new ArrayList<>();
for(Object childEntity: entityList){
dataList.add(transBean2Map(childEntity));
}
map.put(key,dataList);
}
}
}
continue;
}
Object value = getter.invoke(beanObj);
map.put(key, value);
}
}
} catch (Exception e) {
Logger.getAnonymousLogger().log(Level.SEVERE,"transBean2Map Error " + e);
}
return map;
}
But I recommend you to use Google Gson as the JSON deserializer/serializer And the main reason is I hate dealing with exception stuff, it just messed up with the coding style.
And it's pretty easy to satisfy your need with taking advantage of the version control annotation on the bean class like this:
#Since(GifMiaoMacro.GSON_SENSITIVE) //mark the field as sensitive data and will not export to JSON
private boolean firstFrameStored; // won't export this field to JSON.
You can define the Macro whether to export or hide the field like this:
public static final double GSON_SENSITIVE = 2.0f;
public static final double GSON_INSENSITIVE = 1.0f;
By default, Gson will export all field that not annotated by #Since So you don't have to do anything if you do not care about the field and it just exports the field.
And if some field you are not want to export to json, ie sensitive info just add an annotation to the field. And generate json string with this:
private static Gson gsonInsensitive = new GsonBuilder()
.registerTypeAdapter(ObjectId.class,new ObjectIdSerializer()) // you can omit this line and the following line if you are not using mongodb
.registerTypeAdapter(ObjectId.class, new ObjectIdDeserializer()) //you can omit this
.setVersion(GifMiaoMacro.GSON_INSENSITIVE)
.disableHtmlEscaping()
.create();
public static String toInsensitiveJson(Object o){
return gsonInsensitive.toJson(o);
}
Then just use this:
String jsonStr = StringUtils.toInsensitiveJson(yourObj);
Since Gson is stateless, it's fine to use a static method to do your job, I have tried a lot of JSON serialize/deserialize framework with Java, but found Gson to be the sharp one both performance and handily.
We're developing a RESTful API using Java EE 7 (RESTEasy / Hibernate / Jackson).
We want the API to serialize all child entities using their IDs, by default. We're doing this mostly to maintain consistency with our deserialization strategy, where we insist on receiving an ID.
However, we also want our users to be able to choose to get an expanded view of any of our child entities, either through a custom endpoint or a query parameter (undecided). For example:
// http://localhost:8080/rest/operator/1
// =====================================
{
"operatorId": 1,
"organization": 34,
"endUser": 23
}
// http://localhost:8080/rest/operator/1?expand=organization
// =====================================
{
"operatorId": 1,
"organization": {
"organizationId": 34,
"organizationName": "name"
},
"endUser": 23
}
// http://localhost:8080/rest/operator/1?expand=enduser
// =====================================
{
"operatorId": 1,
"organization": 34,
"endUser": {
"endUserId": 23,
"endUserName": "other name"
}
}
// http://localhost:8080/rest/operator/1?expand=organization,enduser
// =====================================
{
"operatorId": 1,
"organization": {
"organizationId": 34,
"organizationName": "name"
},
"endUser": {
"endUserId": 23,
"endUserName": "other name"
}
}
Is there a way to dynamically change the behavior of Jackson to determine whether a specified AbstractEntity field is serialized in full form or as its ID? How might it be done?
Additional Info
We know of a few ways to serialize our child entities using their IDs, including:
public class Operator extends AbstractEntity {
...
#JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="organizationId")
#JsonIdentityReference(alwaysAsId=true)
public getOrganization() { ... }
...
}
and
public class Operator extends AbstractEntity {
...
#JsonSerialize(using=AbstractEntityIdSerializer.class)
public getOrganization() { ... }
...
}
where AbstractEntityIdSerializer serializes the entity using its ID.
The problem is that we don't know of a way for the user to override that default behavior and revert to standard Jackson object serialization. Ideally they'd also be able to choose which child properties to serialize in full form.
It would be awesome to dynamically toggle the alwaysAsId argument of #JsonIdentityReference for any property at runtime, if that's possible, or make the equivalent change to ObjectMapper/ObjectWriter.
Update: Working(?) Solution
We haven't had a chance to fully test this yet, but I've been working on a solution that leverages overriding Jackson's AnnotationIntrospector class. It seems to be working as intended.
public class CustomAnnotationIntrospector extends JacksonAnnotationIntrospector {
private final Set<String> expandFieldNames_;
public CustomAnnotationIntrospector(Set<String> expandFieldNames) {
expandFieldNames_ = expandFieldNames;
}
#Override
public ObjectIdInfo findObjectReferenceInfo(Annotated ann, ObjectIdInfo objectIdInfo) {
JsonIdentityReference ref = _findAnnotation(ann, JsonIdentityReference.class);
if (ref != null) {
for (String expandFieldName : expandFieldNames_) {
String expandFieldGetterName = "get" + expandFieldName;
String propertyName = ann.getName();
boolean fieldNameMatches = expandFieldName.equalsIgnoreCase(propertyName);
boolean fieldGetterNameMatches = expandFieldGetterName.equalsIgnoreCase(propertyName);
if (fieldNameMatches || fieldGetterNameMatches) {
return objectIdInfo.withAlwaysAsId(false);
}
}
objectIdInfo = objectIdInfo.withAlwaysAsId(ref.alwaysAsId());
}
return objectIdInfo;
}
}
At serialization time, we copy our ObjectMapper (so the AnnotationIntrospector runs again) and apply CustomAnnotationIntrospector as follows:
#Context
private HttpRequest httpRequest_;
#Override
writeTo(...) {
// Get our application's ObjectMapper.
ContextResolver<ObjectMapper> objectMapperResolver = provider_.getContextResolver(ObjectMapper.class,
MediaType.WILDCARD_TYPE);
ObjectMapper objectMapper = objectMapperResolver.getContext(Object.class);
// Get Set of fields to be expanded (pre-parsed).
Set<String> fieldNames = (Set<String>)httpRequest_.getAttribute("ExpandFields");
if (!fieldNames.isEmpty()) {
// Pass expand fields to AnnotationIntrospector.
AnnotationIntrospector expansionAnnotationIntrospector = new CustomAnnotationIntrospector(fieldNames);
// Replace ObjectMapper with copy of ObjectMapper and apply custom AnnotationIntrospector.
objectMapper = objectMapper.copy();
objectMapper.setAnnotationIntrospector(expansionAnnotationIntrospector);
}
ObjectWriter objectWriter = objectMapper.writer();
objectWriter.writeValue(...);
}
Any glaring flaws in this approach? It seems relatively straightforward and is fully dynamic.
The answer is Jackson's mixin feature:
You create a simple Java class that has the exact same method signature as the anotated method of the entity. You annotate that method with the modified value. the body of the method is insignificant (it would not be called):
public class OperatorExpanded {
...
#JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="organizationId")
#JsonIdentityReference(alwaysAsId=false)
public Organization getOrganization() { return null; }
...
}
you tie the mixin to the entity-to-be-serialized using Jackson's module system: this can be decided at run time
ObjectMapper mapper = new ObjectMapper();
if ("organization".equals(request.getParameter("exapnd")) {
SimpleModule simpleModule = new SimpleModule();
simpleModule.setMixInAnnotation(Operator.class, OperatorExpanded.class);
mapper.registerModule(simpleModule);
}
now, the mapper will take the annotations from the mixin, but invoke the method of the entity.
If you are looking for a generalized solution that needs to be extended to all of your resources you may try following approach. I tried below solution using Jersey and Jackson. It should also work with RestEasy.
Basically, you need to write a custom jackson provider which set a special serializer for an expand field. Also, you need to pass the expand fields to the serializer so that you can decide how to do the serialization for expand fields.
#Singleton
public class ExpandFieldJacksonProvider extends JacksonJaxbJsonProvider {
#Inject
private Provider<ContainerRequestContext> provider;
#Override
protected JsonEndpointConfig _configForWriting(final ObjectMapper mapper, final Annotation[] annotations, final Class<?> defaultView) {
final AnnotationIntrospector customIntrospector = mapper.getSerializationConfig().getAnnotationIntrospector();
// Set the custom (user) introspector to be the primary one.
final ObjectMapper filteringMapper = mapper.setAnnotationIntrospector(AnnotationIntrospector.pair(customIntrospector, new JacksonAnnotationIntrospector() {
#Override
public Object findSerializer(Annotated a) {
// All expand fields should be annotated with '#ExpandField'.
ExpandField expField = a.getAnnotation(ExpandField.class);
if (expField != null) {
// Use a custom serializer for expand field
return new ExpandSerializer(expField.fieldName(), expField.idProperty());
}
return super.findSerializer(a);
}
}));
return super._configForWriting(filteringMapper, annotations, defaultView);
}
#Override
public void writeTo(final Object value, final Class<?> type, final Type genericType, final Annotation[] annotations, final MediaType mediaType, final MultivaluedMap<String, Object> httpHeaders,
final OutputStream entityStream) throws IOException {
// Set the expand fields to java's ThreadLocal so that it can be accessed in 'ExpandSerializer' class.
ExpandFieldThreadLocal.set(provider.get().getUriInfo().getQueryParameters().get("expand"));
super.writeTo(value, type, genericType, annotations, mediaType, httpHeaders, entityStream);
// Once the serialization is done, clear ThreadLocal
ExpandFieldThreadLocal.remove();
}
ExpandField.java
#Retention(RUNTIME)
public #interface ExpandField {
// name of expand field
String fieldName();
// name of Id property in expand field. For eg: oraganisationId
String idProperty();
}
ExpandFieldThreadLocal.java
public class ExpandFieldThreadLocal {
private static final ThreadLocal<List<String>> _threadLocal = new ThreadLocal<>();
public static List<String> get() {
return _threadLocal.get();
}
public static void set(List<String> expandFields) {
_threadLocal.set(expandFields);
}
public static void remove() {
_threadLocal.remove();
}
}
ExpandFieldSerializer.java
public static class ExpandSerializer extends JsonSerializer<Object> {
private String fieldName;
private String idProperty;
public ExpandSerializer(String fieldName,String idProperty) {
this.fieldName = fieldName;
this.idProperty = idProperty;
}
#Override
public void serialize(Object value, JsonGenerator gen, SerializerProvider serializers) throws IOException, JsonProcessingException {
// Get expand fields in current request which is set in custom jackson provider.
List<String> expandFields = ExpandFieldThreadLocal.get();
if (expandFields == null || !expandFields.contains(fieldName)) {
try {
// If 'expand' is not present in query param OR if the 'expand' field does not contain this field, write only id.
serializers.defaultSerializeValue(value.getClass().getMethod("get"+StringUtils.capitalize(idProperty)).invoke(value),gen);
} catch (Exception e) {
//Handle Exception here
}
} else {
serializers.defaultSerializeValue(value, gen);
}
}
}
Operator.java
public class Operator extends AbstractEntity {
...
#ExpandField(fieldName = "organization",idProperty="organizationId")
private organization;
...
}
The final step is to register the new ExpandFieldJacksonProvider. In Jersey, we register it through an instance of javax.ws.rs.core.Application as shown below. I hope there is something similar in RestEasy. By default, most of the JAX-RS libraries tend to load default JacksonJaxbJsonProvider through auto-discovery. You have to make sure auto-discovery is disabled for Jackson and new ExpandFieldJacksonProvider is registered.
public class JaxRsApplication extends Application{
#Override
public Set<Class<?>> getClasses() {
Set<Class<?>> clazzes=new HashSet<>();
clazzes.add(ExpandFieldJacksonProvider.class);
return clazzes;
}
}