參考文件：https://github.com/FasterXML/jackson-databind

關於ObjectMapper的執行緒安全

截自官方文件：

組合多個物件的屬性構成JSON（以及新增自定義屬性）

Code：

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;

public class
 
 TestJackson {

    private static final ObjectMapper MAPPER = new ObjectMapper();

    public static void main(String[] args) {
        Foo foo = new Foo("value1", "value2");
        Bar bar = new Bar("value3", "value4");
        ObjectNode root = MAPPER.valueToTree(foo);
        ObjectNode node 
 
= MAPPER.valueToTree(bar);
        root.setAll(node);
        root.put("extraFiled", "value5");
        String jsonString = null;
        try {
            jsonString = MAPPER.writerWithDefaultPrettyPrinter().writeValueAsString(root);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }
        System.out.println(jsonString);
    }
}
 

Output：