How to use Jackson to deserialise an array of objects
Jackson is a powerful Java library for processing JSON data. You can use Jackson to deserialize an array of objects by following these steps:
- Add the Jackson dependency to your project. For example, if you are using Maven, you can add the following dependency to your
pom.xml
file:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.11.0</version>
</dependency>
- Create a Java class that represents the object you want to deserialize. For example:
public class User {
private int id;
private String name;
// add getters and setters
}
- Use the
ObjectMapper
class from the Jackson library to deserialize the JSON array. Here's an example of how you can do this:
ObjectMapper mapper = new ObjectMapper();
User[] users = mapper.readValue(jsonString, User[].class);
The readValue()
method takes the JSON string as input and the target class (in this case, User[].class
) as the second argument, and returns an array of objects of the specified class.
You can also use the readValue()
method to deserialize a JSON array into a List
of objects, like this:
ObjectMapper mapper = new ObjectMapper();
TypeReference<List<User>> typeReference = new TypeReference<List<User>>() {};
List<User> users = mapper.readValue(jsonString, typeReference);
This will create a List
of User
objects from the JSON array. The TypeReference
class is used to specify the type of the resulting List
.
Note that the JSON string must be in the correct format for these methods to work correctly. It should be an array of objects, with each object having the same structure as the User
class. For example:
[ { "id": 1, "name": "John" }, { "id": 2, "name": "Jane" }]