Jackson - Deserialising JSON string - TypeReference vs TypeFactory.constructCollectionType

Question

To deserialise JSON string to a list of class, different ways listed at StackOverflow question

Type 1 ( docs link ):

List<SomeClass> someClassList = mapper.readValue(jsonString, typeFactory.constructCollectionType(List.class, SomeClass.class));

Type 2 ( docs link ):

List<SomeClass> list = mapper.readValue(jsonString, new TypeReference<List<SomeClass>>() { });

Though both 2 types above do the job, what is the difference between these implementations ?

Answer 1

After constructing JavaType , both call same deserialization functionality, so the only difference is the way generic type is handled.

Second one is fully static, so type must be known in compile type, and can not vary. So it is similar to using basic Class literal.

First one is dynamic, so it can be used to construct things that vary regarding their parameterization.

Personally I prefer first alternative for all cases (it avoids creation of one more anonymous inner classes), but second one may be more readable.

Answer 2

实现这一目标的另一种方法是：

List<SomeClass> list = Arrays.asList(mapper.readValue(jsonString, SomeClass[].class));