Java JSON Data Binding Example ( jackson processor)

Java JSON data Binding

JSON (JavaScript Object Notation), is a simple and easy to read and write data exchange format. In this tutorial
we focus three opensource java library which process the json data, which are Jackson, Google Gson and JSON.simple.

Jackson

It is a high performance JSON processor. There are some examples given here.

Jackson data binding example-Object & JSON :

In this example we are showing how to convert java object to/from JSON.
before starting with jackson, you have to download the library and include in your java classpath from Here
Create a POJO:
Person object, initialized with some values
package json.test; import java.util.ArrayList; import java.util.List; public class Person { private int age = 29; private String name = "Wakil"; private List<String> messages = new ArrayList<String>() { { add("Message 1"); add("Message 2"); add("Message 3"); } }; public int getAge() { return age; } public void setAge(int age) { this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<String> getMessages() { return messages; } public void setMessages(List<String> messages) { this.messages = messages; } @Override public String toString() { return "Person [age=" + age + ", name=" + name + ", " + "messages=" + messages + "]"; } }
Java Object to JSON:
Convert an Person object into JSON formatted string, and save it into a file person.json.
package json.test; import java.io.File; import java.io.IOException; import org.codehaus.jackson.JsonGenerationException; import org.codehaus.jackson.map.JsonMappingException; import org.codehaus.jackson.map.ObjectMapper; public class JacksonTest { public static void main(String[] args) { ObjectMapper mapper = new ObjectMapper(); Person person =new Person(); try { // convert person object to json string, and save to a file mapper.writeValue(new File("d:\\test\\person.json"), person); // display to console System.out.println(mapper.writeValueAsString(person)); } catch (JsonGenerationException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }
Output will be
{"name":"Wakil","age":29,"messages":["Message 1","Message 2","Message 3"]}

JSON to Java Object:
Read JSON string from file person.json, and convert it back to Java object.
package json.test; import java.io.File; import java.io.IOException; import org.codehaus.jackson.JsonGenerationException; import org.codehaus.jackson.map.JsonMappingException; import org.codehaus.jackson.map.ObjectMapper; public class JacksonToJava { public static void main(String[] args) { ObjectMapper mapper = new ObjectMapper(); try { // read from file, convert it to person class Person user = mapper.readValue(new File("d:\\test\\person.json"), Person.class); // display to console System.out.println(user); } catch (JsonGenerationException e) { e.printStackTrace(); } catch (JsonMappingException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }
Output will be Person [age=29, name=Wakil, messages=[Message 1, Message 2, Message 3]]