What is the best way to convert a JSON string received from Angular into a Java Object within a Spring

Question

What is the best way to convert a JSON string received from Angular into a Java Object within a Spring

I am currently utilizing WebSocket to create a chat application.

Below is the code from my Angular application that sends a MessageModel object to the backend after converting it into a JSON string:

sendMessage(message: MessageModel){
let data = JSON.stringify({
  message: message
})    
this.ws.send("/messaging/"+message.receiverId, {}, data); }

Here is the Java code responsible for receiving the message:

@MessageMapping("/messaging/{to}")
@SendTo("/inbox/coversation/{to}")
public String processMessageFromClient(@DestinationVariable String to, @Payload String message) throws Exception {
    MessageModel msg = new MessageModel();
    System.out.println(message);

    msg = new Gson().fromJson(message, MessageModel.class);
    System.out.println(msg);

    return message;
}

The output of System.out.println(message) shows:

{"message":{"messageText":"hey","senderId":4,"senderName":"Akash Malhotra","receiverId":1,"senderEmail":"[email protected]","sentTime":"15:19:43 GMT+0530 (India Standard Time)","date":"08/06/2020, 15:19:43"}}

and

The output of System.out.println(msg) displays:

MessageModel [messageText=null, senderName=null, senderId=null, senderEmail=null, profilePicUrl=null, receiverId=null, sentTime=null, date=null]

QUERY: I am seeking help on how to properly set the 'String message' received from Angular into my MessageModel object in Java as it currently shows all null values.

java angular spring-boot websocket stomp

Answer 1

Answer №1

Summary: Success!

public class ProblemSolved
{
    public String analyzeClientMessage( String recipient, String text ) throws Exception
    {
        System.out.println( text );

        final MessagePack pack = new Gson().fromJson( text, MessagePack.class );
        System.out.println( pack.text );

        return text;
    }

    public static void main( String[] args ) throws Exception
    {
        final String jsonData = "{\"text\":{\"messageText\":\"hello\",\"senderId\":4,\"senderName\":\"John Doe\",\"receiverId\":1,\"senderEmail\":\"john.doe@example.com\",\"sentTime\":\"15:19:43 GMT+0530 (India Standard Time)\",\"date\":\"08/06/2020, 15:19:43\"}}";
        new ProblemSolved().analyzeClientMessage( "Me", jsonData );
    }
}

class MessageData
{
    String messageText;
    String senderName;
    Integer senderId;
    String senderEmail;
    String profilePicUrl;
    Integer receiverId;
    String sentTime;
    String date;

    @Override
    public String toString()
    {
        // ... etc.
    }
}

class MessagePack
{
    MessageData text;
}

Detailed Explanation:

The provided JSON string includes an inner layer wrapped as follows:

{
    "text" = { /* properties of MessageData */ }
}

As the MessageData structure lacks a text field, the values are not assigned and end up as null. By encapsulating MessageData inside another class called MessagePack that contains a text field of type MessageData, GSON can effectively parse the contents of the MessageData.

Answer 2

Summary: Success!

public class ProblemSolved
{
    public String analyzeClientMessage( String recipient, String text ) throws Exception
    {
        System.out.println( text );

        final MessagePack pack = new Gson().fromJson( text, MessagePack.class );
        System.out.println( pack.text );

        return text;
    }

    public static void main( String[] args ) throws Exception
    {
        final String jsonData = "{\"text\":{\"messageText\":\"hello\",\"senderId\":4,\"senderName\":\"John Doe\",\"receiverId\":1,\"senderEmail\":\"john.doe@example.com\",\"sentTime\":\"15:19:43 GMT+0530 (India Standard Time)\",\"date\":\"08/06/2020, 15:19:43\"}}";
        new ProblemSolved().analyzeClientMessage( "Me", jsonData );
    }
}

class MessageData
{
    String messageText;
    String senderName;
    Integer senderId;
    String senderEmail;
    String profilePicUrl;
    Integer receiverId;
    String sentTime;
    String date;

    @Override
    public String toString()
    {
        // ... etc.
    }
}

class MessagePack
{
    MessageData text;
}

Detailed Explanation:

The provided JSON string includes an inner layer wrapped as follows:

{
    "text" = { /* properties of MessageData */ }
}

As the MessageData structure lacks a text field, the values are not assigned and end up as null. By encapsulating MessageData inside another class called MessagePack that contains a text field of type MessageData, GSON can effectively parse the contents of the MessageData.

Answer 3

Answer №2

To enhance your method, pass MessageModel instead of a String as an argument. Spring will utilize the underlying jackson (or a specific mapper you have configured for Spring) to convert the payload into a MessageModel object through the designated MessageModel class.

@MessageMapping("/messaging/{to}")
@SendTo("/inbox/conversation/{to}")
public String processMessageFromClient(@DestinationVariable String to, @Payload MessageModel message) throws Exception {
    ...
}

Answer 4

To enhance your method, pass MessageModel instead of a String as an argument. Spring will utilize the underlying jackson (or a specific mapper you have configured for Spring) to convert the payload into a MessageModel object through the designated MessageModel class.

@MessageMapping("/messaging/{to}")
@SendTo("/inbox/conversation/{to}")
public String processMessageFromClient(@DestinationVariable String to, @Payload MessageModel message) throws Exception {
    ...
}

What is the best way to convert a JSON string received from Angular into a Java Object within a Spring

Answer №1

Summary: Success!

Detailed Explanation:

Answer №2

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