JarCastinggroovy-beans-with-jackson
Implementations of the Jackson API to support Groovy Beans, particularly @Immutables
Current Status
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Use Cases
Groovy Beans are a particularly attractive way of developing Java Beans. Yet when making the most of what Groovy provides, particularly the @Immutable transform, this presents challenges during deserialization as Jackson will not be able to find a default constructor (or any annotations if your classes are fully Groovy).
Consider the following Groovy Bean.
@Immutable
class BeanBag {
Integer count
String texture
Zipper zipper
}
Without modification, this stacktrace might look familiar:
com.fasterxml.jackson.databind.JsonMappingException:
No suitable constructor found for type
[simple type, class BeanBag]:
can not instantiate from JSON object (need to add/enable type information?)
As a first naive step, one could provide a private constructor:
@Immutable
class BeanBag {
private BeanBag() {}
Integer count
String texture
Zipper zipper
}
And would could expect to receive this message:
Groovyc: Explicit constructors not allowed for @Immutable class: BeanBag
Yet, the @Immutable transform prohibits this, any other constructors are also forbidden.
In Use
In order to deserialize @Immutable GroovyBeans without fuss, simply provide the ObjectMapper with a Jackson Module which provides the necessary ValueInstantiator to allow Jackson to instantiate GroovyBeans by their generated HashMap constructors.
ObjectMapper objectMapper = new ObjectMapper()
objectMapper.registerModule(new GroovyImmutableModule())
// this is now possible.
BeanBag beanBag = objectMapper.readValue('{"count": 100, "texture": "smooth"}', BeanBag)
Coordinates
You may make use of this module with the following coordinates:
Maven
<dependency>
<groupId>com.phasebash.jackson</groupId>
<artifactId>groovy-beans-with-jackson-immutables-module</artifactId>
<version>1.0</version>
</dependency>
Gradle
compile(
[groupId: 'com.phasebash.jackson', name: 'groovy-beans-with-jackson-immutables-module', version: '1.0']
)
Questions, Feedback?
Feel free to submit an issue ticket through github or contact me directly. I will help you.
License
The groovy-beans-with-jackson has been released under Apache 2.0 as per all it's dependencies.