Jackson deserialize interface with single implementation

Polymorphism is the ability to have different implementations represented by a single interface or abstract class. This article describes how to serialize and deserialize objects by their interface, as well as Polymorphic Tree Structured object instances. Please note this example is written in Java 8 and uses Lombok. Lombok has numerous benefits like generating getters, toString, equals and hashcode methods. Check Jackson Databind on Maven Central. The Vehicle interface has two implementations: Car and Truck.

In order to do this, Jackson Json must be configured. There are several ways to do so.

Custom Jackson Polymorphic Deserialization without Type Metadata

In the following example, the mapping is directly configured on the Vehicle interface:. This solution works well when the interface and the implementation are placed within the same package. However, it introduces a cyclic dependency between the Vehicle interface and its implementations. The other solution is the configure the type mapping separately on the ObjectMapper. Jackson has added a type attribute to each vehicle json.

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This special attribute is used to identify the type of vehicle being serialized. Jackson then uses this information during deserialization to create the right class instance. Here is an example:.

Java and JSON – Jackson Serialization with ObjectMapper

A CarTransporter is a Vehicle itself! The produced json looks like the following:. I hope you see now that there is nothing difficult here! Jackson can serialize and deserialize polymorphic data structures very easily. Now, you know how to configure Jackson to serialize and deserialize objects being represented by their interface. Thanks for your article, it was helpful. Question: How do you get the vehicles list to print without the list type info, i.Awesome, exactly what I needed Excellent article.

Have you ever run into the situation like Example 5, but you have multiple types pointing to one parent class. I think I found a bug in Jackson, because I tried two types pointing to the same class and it ignores the second one. File; import java. Collection; import org. JsonSubTypes; import org. Type; import org.

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JsonTypeInfo; import org. For the interested, I logged Jackson issue for an enhancement to provide non-annotation-based subtype registration. Don't hesitate to vote for the issue if you want it implemented.

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If you add constructors to example 6 it no longer works. There is a unable to find suitable constructor error. I wish to have immutable classes so making all parameters final is required. I can easily know the class but that doesn't help. How do I deal with classes that are available to me as jar files with no source code provided? Example: if the source code of the Animal class file is not available, how do I annotate the class with Jackson annotations? I'm another new Jackson user, and I'm looking for a way to do this also.

Write your own deserializer and infer the classes to bind to from the json attributes. You may want to use "mix-in annotations" -- these allow associating annotation values without modifying target classes. This is an excellent example, and it's really helped me what I'm trying to do. I've extended example 5 to resolve the JSON coming from a database field into the appropriate object and produced a suite of tests so that I'm satisfied it's reading and writing them correctly.

If I don't use the mapper and allow the Jackson default parsing to serialize the object, then the type element is lost when I examine the output from the feed. I don't want to have to do any post processing in the back end or preprocessing in the front end to overcome this.

Example 6 works great if the base class is abstract. But what happens if the base class itself is not abstract and can be instantiated? You can simply conclude that it is actually the base class because it does NOT have any of the registered attributes.

But the line return mapper. How can I resolve this if adding an additional abstract base class is not possible? Great article! Is that a limitation of Jackson, or a limitation of json-schema. Any idea how to solve this?By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Because the target is an interface I need to specify which implementation should be used. But I want to specify the implementation in source code because it's always the same.

Use a SimpleAbstractTypeResolver :. This question was answered a while ago but I want to give you another option that doesn't require to tune ObjectMapper and also much simpler then JsonTypeInfo annotation. How are we doing? Please help us improve Stack Overflow. Take our short survey. Learn more. Jackson - How to specify a single implementation for interface-referenced deserialization?

Ask Question. Asked 7 years, 6 months ago. Active 2 years, 7 months ago. Viewed 28k times. Is this possible? Ben Barkay 4, 1 1 gold badge 15 15 silver badges 28 28 bronze badges. Max Schmidt Max Schmidt 5, 5 5 gold badges 19 19 silver badges 28 28 bronze badges. The question here is about a single implementation, but one could research about inheritance in general, and we should then see the JsonTypeInfo annotation.

Active Oldest Votes. Marco Altieri 2, 2 2 gold badges 23 23 silver badges 38 38 bronze badges.

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David Grant David Grant Thanks, I just found an alternative if you want to specify the concrete implementation as an annotation wiki. Sounds like a nice compromise! There is another approach that will work if you have just single interface implementation. Ilya Ovesnov Ilya Ovesnov 3, 1 1 gold badge 16 16 silver badges 29 29 bronze badges. This is by far the best answer to the OP question.

Gaurav this answer should help you: stackoverflow. Jason Smiley Jason Smiley 91 1 1 silver badge 3 3 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Cryptocurrency-Based Life Forms. Q2 Community Roadmap. Featured on Meta.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

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Already on GitHub? Sign in to your account. Related question: How to abstractly deserialize different enum types with Jackson based on common field? After trace source code, and I find line in com.

DeserializerCacheit will judge was not enum type first, and ignore my custom deserializer deserializers. First of all, having generic parameter for an Enum should not make any difference: deserializers are matched by default based on type-erased Class.

Similarly, an enum implementing an interface will not have any effect either by default Jackson will only consider enum type or with respect to choosing custom deserializer.

However, your code does not show how you are registering deserializers so it is difficult to say what is going on. One thing to note is, however, that you MUST register ALL deserializers and serializers before any use -- it is not possible to change registrations after calling readValue.

jackson deserialize interface with single implementation

So perhaps this is causing an issue? However, I could not modify TestEnum. That's why I make a custom deserializer. GoldyMark yes, but what does bean. I assume it's defined in Jackson2ObjectMapperFactoryBeanand may try to set deserializer when called. If so, code is broken as it would try to add deserializer after using ObjectMapper : this will not work, and in practice will just use whatever deserializer was in use first time given type was deserialized.

The target will be resolved to first E type enum and will not changed anymore. I'm curious is there a way to get JavaType in deserialize method? There is no point, either, as static information from property can not change.

If you want to retain type, you will need to keep track of it either via constructor when originally createdor through createContextual.

At this point I do not see a problem in Jackson itself: it seems likely that Spring mapping of custom deserializer does not take effect. Jackson does allow registration of deserializer by any type, enum or not. This seems overcomplicated to me. This message could seem a little bit misleading as it says that t1, t2 and n are the Enum names while those are values of our 'id' property, but this is what we marked as actual representation by putting JsonValue annotation on in.

As you see only JsonValue is there and both serialization and deserialization works. I'm using Jackson in version 2. Support for using JsonValue also for deserialization was indeed added at some point to reduce duplication; while I can't find the issue closes I saw was it's been there for a while and definitely in 2. GoldyMarkCould you find any solution for your issue?

I am facing exact same issue. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue. Jump to bottom.

jackson deserialize interface with single implementation

How to deserialize enum which implements generic interface in jackson? Copy link Quote reply. Now, I completed serialize, but fail on deserialize look at below codes.

jackson deserialize interface with single implementation

TYPE1 ; System.First method is simpler in that no registration is needed: when values of types that implement JsonSerializable are encountered, serialize method is called to serialize the instance.

Jackson 1. This is the recommended way to add custom serializers -- all serializers are considered "generic", in that they are used for subtypes unless more specific binding is found. The simplest way is to extend SimpleModule, add serializer sand register module with ObjectMapper:.

For more advanced handling of types to serializers you may need to implement Module interface directly; this will give more control over exact matching logic. This may be necessary when dealing with generic types especially Maps and Collections. Before Jackson 1. Note that starting with 1. If you want to output some other JSON value instead of null mainly because some other processing tools prefer other constant values -- often empty Stringthings are bit trickier as nominal type may be anything; and while you could register serializer for Object.

Skip to content. Jackson How-To: Custom Serializers Alternative Methods There are two general mechanisms for enabling fully customized serialization: Make value class to be serialized implement interface org. JsonSerializableWithType : this is similar to implementing java. Serializable in that a method serialize of value class is called to handle serialization.

NOTE: prior to Jackson 1. JsonSerializable ; but this is now deprecated since it did not support handling of possible additional type information see JacksonPolymorphicDeserialization for details. If choosing to use this method, consider starting with a partial implementation such as org.

JsonSerializer to create an external serializer that can be registered to handle values of certain types or more specifically values of certain properties First method is simpler in that no registration is needed: when values of types that implement JsonSerializable are encountered, serialize method is called to serialize the instance. Registering external serializers There are multiple ways to do register external serializers: By using annotations: Classes and methods can be annotated using JsonSerialize.

With Jackson 1. SerializerFactory Either use or extend existing implementation, org. CustomSerializerFactory or even implement one from scratch if it doesn't work for you Add mappings from serialized Class to JsonSerializer instance by calling addSpecificMapping or addGenericMapping check out JavaDocs for explanation on difference Custom serializer factory needs to be registered with ObjectMapper. Specific use cases Converting null values to something else like empty Strings If you want to output some other JSON value instead of null mainly because some other processing tools prefer other constant values -- often empty Stringthings are bit trickier as nominal type may be anything; and while you could register serializer for Object.

Footer Placeholder. Pages You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window.Our job is to integrate with these APIs, normalize them, and distribute the data in web- and mobile-friendly web services. One of the scenarios we often encounter is a provider supplying multiple resource JSON-based APIs that share a lot of the same data in their responses, but without any particular field dedicated to identying the type of the resource e.

Instead of mapping 1-to-1 with these APIs, we often try to follow DRY principles and model them as implementations of a common polymorphic abstraction. When using Jackson for polmorphic deserialization and not being in control of the API response data, the lack of any kind of type identifier requires a different solution. The deserialize method reads each of the fields in the response and looks up the registry to see if it is present.

Deserializing Interface Properties using Json.Net

If it finds a match, the mapper. If no match is found an exception is thrown. For the unit test, I created an inner static abstract class AbstractTestObject containing shared data with two concrete implementations TestObjectOne and TestObjectTwo that each contain a property unique to that type.Polymorphism is the ability to have different implementations represented by a single interface or abstract class. This article describes how to serialize and deserialize objects by their interface, as well as Polymorphic Tree Structured object instances.

Please note this example is written in Java 8 and uses Lombok. Lombok has numerous benefits like generating getters, toString, equals and hashcode methods. Check Jackson Databind on Maven Central. The Vehicle interface has two implementations: Car and Truck. In order to do this, Jackson Json must be configured. There are several ways to do so.

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In the following example, the mapping is directly configured on the Vehicle interface:. This solution works well when the interface and the implementation are placed within the same package. However, it introduces a cyclic dependency between the Vehicle interface and its implementations. The other solution is the configure the type mapping separately on the ObjectMapper. Jackson has added a type attribute to each vehicle json. This special attribute is used to identify the type of vehicle being serialized.

Jackson then uses this information during deserialization to create the right class instance. Here is an example:. A CarTransporter is a Vehicle itself! The produced json looks like the following:. I hope you see now that there is nothing difficult here! Jackson can serialize and deserialize polymorphic data structures very easily.

Now, you know how to configure Jackson to serialize and deserialize objects being represented by their interface. Thanks for your article, it was helpful.


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