Luis Gómez Caballero Software Development

Jackson is a tool that allows, amonth other things, to transform Java object to JSON objects and viceversa. We are going to create a project to demonstrate how this technology works.

Project creation

We create a Maven project.

Jackson libraries import

We have to update the pom.xml file and add the following dependencies:

<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-databind</artifactId>
	<version>2.9.3</version>
</dependency>
<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-annotations</artifactId>
	<version>2.9.3</version>
</dependency>
<dependency>
	<groupId>com.fasterxml.jackson.core</groupId>
	<artifactId>jackson-core</artifactId>
	<version>2.9.3</version>
</dependency>

Mapper object

Jackson gives us a mapper object that we will use to perform the tansformations. This is the ObjectMapper.

ObjectMapper mapper = new ObjectMapper();

Java Bean example

package app;

public class MyObject {
	private String myString;
	private int myInt;

	public MyObject() {
		super();
	}

	public MyObject(String myString, int myInt) {
		super();
		this.myString = myString;
		this.myInt = myInt;
	}

	public String getMyString() {
		return myString;
	}

	public void setMyString(String myString) {
		this.myString = myString;
	}

	public int getMyInt() {
		return myInt;
	}

	public void setMyInt(int myInt) {
		this.myInt = myInt;
	}

	@Override
	public String toString() {
		return "MyObject [myString=" + myString + ", myInt=" + myInt + "]";
	}

}

We are going to use a JSON object that we will transform into a Java object. We will transform this last Java object to a JSON object.

JSON to Java transformation

In our case we are going to use a JSON text string. It is very simple to do so:

String jsonInputString = "{\"myString\":\"abc\", \"myInt\":123}";
MyObject myObject = mapper.readValue(jsonInputString, MyObject.class);

Java to JSON transformation

It is also simple:

String jsonOutputString = mapper.writeValueAsString(myObject);

The code of this project is situated at https://github.com/luisgomezcaballero/jackson-json.

Luis Gómez Caballero