将JSON字符串反序列化为自定义Java对象

Question

I have a string that is returned to me that is formatted as a JSON. The string looks as follows

{ "Type" : "Notification". "MessageId" : "9343.....". "TopicArn" : "arn-....." "......" }

I have created a custom object that I would like to parse this string into

public class AmazonSNSMessage 
{
private String Type;
private String Notification;
private String MessageId;
private String TopicArn;
private String Subject;
private String Message;
private String Timestamp;
private String SignatureVersion;
private String Signature;
private String UnsubscribeURL

// And all the appropriate get/set methods
}

Is there a JSON deserializer in Java that will take the string and create an instance of the AmazonSNSMessage?

C# Does this by calling this line

AmazonSNSMessage b = JsonConvert.DeserializeObject<AmazonSNSMessage>(TheString);

and ideally I would like something similar.

Answer 1

Jackson can do that:

final ObjectMapper mapper = new ObjectMapper();

final AmazonSNSMessage message 
    = mapper.readValue(yourInput, AmazonSNSMessage.class);

It will work automatically since your field names are the same as JSON!

If you have more complex scenarios, you can use annotations, custom deserializers etc.

Answer 2

I would suggest to use the next library,

https://code.google.com/p/json-simple/

I have used it, and it is pretty easy.

Answer 3

http://code.google.com/p/google-gson/

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

Answer 4

A mode of comment, as fge says, Jackson is a very powerful library to handle Json serialization and deserialization. Its very nice map json keys to POJO attributes to get a consistent camel cased code using annotations.

public class AmazonSNSMessage 
{
    @JsonProperty("Type");
    private String type;

    @JsonProperty("Notification");
    private String notification;

    @JsonProperty("MessageId");
    private String messageId;

    @JsonProperty("TopicArn");
    private String topicArn;

    @JsonProperty("Subject");
    private String subject;

    @JsonProperty("Message");
    private String message;

    @JsonProperty("Timestamp");
    private Date timestamp;

    @JsonProperty("SignatureVersion");
    private String signatureVersion;

    @JsonProperty("Signature");
    private String signature;

    @JsonProperty("UnsuscribeUrl");
    private String unsubscribeURL

    // And all the appropriate get/set methods
}