使用Jackson将Tree转换为Json，但没有方括号和字段名

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class TreeToJsonExample {
    public static void main(String[] args) throws Exception {
        // 创建JsonFactory和JsonGenerator
        JsonFactory factory = new JsonFactory();
        JsonGenerator generator = factory.createGenerator(System.out);

        // 创建ObjectMapper和JsonNode
        ObjectMapper mapper = new ObjectMapper();
        JsonNode tree = mapper.createObjectNode()
                .put("name", "John")
                .put("age", 30);

        // 将Tree转换为Json
        generator.writeTree(tree);

        // 关闭JsonGenerator
        generator.close();
    }
}

{"name":"John","age":30}