ObjectMapper：如何在蛇案例中获取根元素

Question

我正在尝试读取对象并转换为字符串。但是根元素正在从payment_token 更改为PaymentToken。

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(Include.NON_NULL);
mapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true);
mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
String requestString = mapper.writeValueAsString(paymentToken); //paymenttoken is valid object

输入对象：

{
    "payment_token": {
        "client_id": "test",
        "currency_code": "USD" 
    }
}

获取输出为：

{
    "PaymentToken": {
        "client_id": "test",
        "currency_code": "USD"
    }
}

帮我获取输入中的根对象？

Answer 1

你可以如下使用

import com.fasterxml.jackson.annotation.JsonRootName;
@JsonRootName(value = "payment_token")
public class PaymentToken {
...
}

参考：JsonRootName

如果你添加上面的注释，让我们看看它是如何工作的
在 ObjectMapper 中添加如下配置

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.SerializationFeature;

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
mapper.configure(SerializationFeature.WRAP_ROOT_VALUE, true);
mapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, true); // additional to your config
mapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
String paymentToken = "{\"payment_token\":{\"client_id\":\"test\",\"currency_code\":\"USD\"}}";

System.out.println(mapper.readValue(paymentToken, PaymentToken.class));
System.out.println(mapper.writeValueAsString(paymentToken));

输出：

PaymentToken(clientId=test, currencyCode=USD)
{"String":"{\"payment_token\":{\"client_id\":\"test\",\"currency_code\":\"USD\"}}"}

如上所见，objectMapper 正确反序列化和序列化。