Java function with Map.Class parameter in Scala

Question

I'm trying to use a Jackson's ObjectMapper() function: convertValue.

It takes 2 parameters (3 overloads):

1. (Object, Call)
2. (Object, TypeReference)
3. (Object, JavaType)

I have the following code:

val m = new ObjectMapper()
val map: Map[String, Object] = m.convertValue(bean, classOf[Map])

which doesn't work with error Type Mismatch. Expected JavaType actual Class[Map].

I tested with classOf[java.util.Map], Map.getClass, etc. but can't make it work.

How should I send that parameter?

Answer 1

Step 1: look at https://fasterxml.github.io/jackson-databind/javadoc/2.8/com/fasterxml/jackson/databind/JavaType.html. See

Instances can (only) be constructed by com.fasterxml.jackson.databind.type.TypeFactory.

Step 2: look at https://fasterxml.github.io/jackson-databind/javadoc/2.8/com/fasterxml/jackson/databind/type/TypeFactory.html.

Then you can see it can be used as e.g.

m.getTypeFactory.constructMapType(classOf[java.util.Map[_, _]], classOf[YourKey], classOf[YourValue])

• Fede E.: This throws me: java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to scala.runtime.Nothing$

Answer 2

You can use the mapper to get the JavaType, for example:

val stringType:JavaType = mapper.constructType(String.class);

You can try the following for your problem:

val m = new ObjectMapper()
val mapType:JavaType = mapper.constructType(java.util.Map.class)
val map: Map[String, Object] = m.convertValue(bean, mapType)