How to Deserialize JSON Arrays of Objects using Jackson?

Deserializing Array of Objects using Jackson

When dealing with JSON data, it is often necessary to parse arrays of objects. Jackson, a popular Java library for data binding, provides support for deserializing such structures.

Jackson's documentation states that it can deserialize "Arrays of all supported types." However, the specific syntax for this process may not be immediately apparent. To clarify the deserialization of arrays using Jackson, let's explore the following scenario:

Deserializing a Single Object

Consider the following JSON input:

{
    "id" : "junk",
    "stuff" : "things"
}

To deserialize this JSON into a Java object named MyClass, we would use the following code:

//json input
{
    "id" : "junk",
    "stuff" : "things"
}

//Java
MyClass instance = objectMapper.readValue(json, MyClass.class);

Deserializing an Array of Objects

For an array of MyClass objects, the JSON input would look like this:

[{
    "id" : "junk",
    "stuff" : "things"
},
{
    "id" : "spam",
    "stuff" : "eggs"
}]

To deserialize this array into a Java List of MyClass objects, we have two options:

As Array:

MyClass[] myObjects = mapper.readValue(json, MyClass[].class);

As List:

List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>() {});

Alternatively, we can specify the List type as:

List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));

By following these methods, you can effectively deserialize arrays of objects using Jackson and conveniently access their contents in your Java code.

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