JSONConversion.md

JSON

Introduction

In our project we use JSON to submit and receive messages. A POJO (plain old java object) can be transformed to a JSON string automatically, and we can also automatically create object instances based on JSON strings. As a simple example, the JSON object {"title": "Some Title", "id": "42"} can be transformed into a Java object instance for the following class:

public class Test {
  public String title;
  public long id;
}

In this object instance the fields are set accordingly.

Technical Aspects

We use the Jackson project to do this conversion. By registering the JacksonJsonProvider bean CXF automatically uses Jackson when a JSON String or POJO needs to be converted. For this to work, the following aspects need to be regarded:

• The Content-Type of incoming requests containing JSON data must be set to application/json
• POJOs are only converted to JSON if the REST controller produces JSON
• Jackson by default uses the default constructor (no arguments) to create a new object instance. If you implement another constructor, make sure to also add the default constructor explicitly.
• In the default configuration, the fields must be public, or you need to provide public setter and getter methods. These methods must follow the setName and getName pattern. For boolean values also isName is accepted.
• Jackson can be configured using annotations, e.g. @JsonIgnoreProperties(ignoreUnknown=true) to ignore additional fields in the JSON string or you can
• configure your own JacksonJsonProvider:

JacksonJsonProvider jsonProvider = new JacksonJsonProvider()
				.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

Further settings are documented here