Java Jackson的多态反序列化问题
我有以下几个类,我想使用Jackson反序列化JSON字符串 PushNotificationMessage.javaJava Jackson的多态反序列化问题,java,json,jackson,deserialization,json-deserialization,Java,Json,Jackson,Deserialization,Json Deserialization,我有以下几个类,我想使用Jackson反序列化JSON字符串 PushNotificationMessage.java public class PushNotificationMessage { @JsonProperty("device_info") private DeviceInfo deviceInfo; private String content; //getters & setters } public class DeviceInfo
public class PushNotificationMessage {
@JsonProperty("device_info")
private DeviceInfo deviceInfo;
private String content;
//getters & setters
}
public class DeviceInfo {
@JsonProperty(value = "device_type")
private String deviceType;
//getters & setters
}
public class IOSDeviceInfo extends DeviceInfo {
@JsonProperty(value = "device_id")
private String deviceId;
private String arn;
@JsonProperty(value = "user_data")
private String userData;
//getters & setters
}
public class WebDeviceInfo extends DeviceInfo {
private String endpoint;
private String key;
private String auth;
//getters & setters
}
DeviceInfo.java
public class PushNotificationMessage {
@JsonProperty("device_info")
private DeviceInfo deviceInfo;
private String content;
//getters & setters
}
public class DeviceInfo {
@JsonProperty(value = "device_type")
private String deviceType;
//getters & setters
}
public class IOSDeviceInfo extends DeviceInfo {
@JsonProperty(value = "device_id")
private String deviceId;
private String arn;
@JsonProperty(value = "user_data")
private String userData;
//getters & setters
}
public class WebDeviceInfo extends DeviceInfo {
private String endpoint;
private String key;
private String auth;
//getters & setters
}
IOSDeviceInfo.java
public class PushNotificationMessage {
@JsonProperty("device_info")
private DeviceInfo deviceInfo;
private String content;
//getters & setters
}
public class DeviceInfo {
@JsonProperty(value = "device_type")
private String deviceType;
//getters & setters
}
public class IOSDeviceInfo extends DeviceInfo {
@JsonProperty(value = "device_id")
private String deviceId;
private String arn;
@JsonProperty(value = "user_data")
private String userData;
//getters & setters
}
public class WebDeviceInfo extends DeviceInfo {
private String endpoint;
private String key;
private String auth;
//getters & setters
}
WebDeviceInfo.java
public class PushNotificationMessage {
@JsonProperty("device_info")
private DeviceInfo deviceInfo;
private String content;
//getters & setters
}
public class DeviceInfo {
@JsonProperty(value = "device_type")
private String deviceType;
//getters & setters
}
public class IOSDeviceInfo extends DeviceInfo {
@JsonProperty(value = "device_id")
private String deviceId;
private String arn;
@JsonProperty(value = "user_data")
private String userData;
//getters & setters
}
public class WebDeviceInfo extends DeviceInfo {
private String endpoint;
private String key;
private String auth;
//getters & setters
}
我想反序列化以下JSON内容:
{
"device_info": {
"endpoint": "https://android.googleapis.com/gcm/send/blah",
"key": "blahkey",
"auth": "blahauth",
"device_type": "web"
},
"content": "Notification content"
}
我只是简单地使用ObjectMapper
来尝试执行反序列化
final ObjectMapper objectMapper = new ObjectMapper();
final PushNotificationMessage message = objectMapper.readValue(jsonString, PushNotifictionMessage.class);
当我这样做时,我得到:
com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException:无法识别的字段“endpoint”(class com.blah.DeviceInfo),未标记为可忽略(一个已知属性:“device_type”])
我如何让Jackson认识到它需要映射到WebDeviceInfo
实例,而不是尝试将其映射到没有端点
字段的DeviceInfo
超类
我曾尝试在不同的类中使用@JsonTypeInfo
和@JsonSubTypes
注释,但我找不到如何使用它们的好例子
EDIT:我在我的DeviceInfo
类中添加了@jsondeseserialize(使用=DeviceInfoDeserializer.class)
注释,并创建了以下DeviceInfoDeserializer
public class DeviceInfoDeserializer extends JsonDeserializer<DeviceInfo> {
private static final String DEVICE_TYPE = "device_type";
private static final String WEB = "web";
private static final String IOS = "ios";
@Override
public DeviceInfo deserialize(final JsonParser jsonParser, final DeserializationContext deserializationContext) throws IOException {
final ObjectMapper objectMapper = (ObjectMapper) jsonParser.getCodec();
final ObjectNode root = objectMapper.readTree(jsonParser);
if (root.has(DEVICE_TYPE)) {
final JsonNode jsonNode = root.get(DEVICE_TYPE);
if (jsonNode.asText().equalsIgnoreCase(WEB)) {
return objectMapper.readValue(root.toString(), WebDeviceInfo.class);
} else if (jsonNode.asText().equalsIgnoreCase(IOS)) {
return objectMapper.readValue(root.toString(), IOSDeviceInfo.class);
}
}
throw deserializationContext.mappingException("Failed to de-serialize device info, as device_type was not \"web\" or \"ios\"");
}
}
编辑:只需将
@jsondeservialize(as=WebDeviceInfo.class)
和@jsondeservialize(as=IOSDeviceInfo.class)
添加到我的子类中,现在它可以正常工作了。非常感谢。Jackson没有意识到多态性,它只是尝试创建一个具体DeviceInfo类的实例
但是,您可以实现一个自定义反序列化程序,该程序以编程方式解析设备信息JSON,并知道由于某些字段(如端点
)的唯一性,何时实例化其中一个子类
这里可以找到一个例子:用
@jsondeseligate(as=IOSDeviceInfo.class)
和@jsondeseligate(as=WebDeviceInfo.class)
注释的子类是否与示例中一样?是的,这就是问题所在。谢谢,这正是我想要的。