Hyperledger Java SDK Client Event Listener to register and listen Blocks

Question

I am using Java SDK based client for the Hyperledger fabric and i am trying to register and listen to BLOCK and CHAINCODE events. I want to create a separate thread for this. 

HFClient client = HFClient.createNewInstance();
Channel channel = client.newChannel("channel01");
EventHub eventHub = client.newEventHub("eh01", "grpc://abc.xyz.us:7053");
channel.addEventHub(eventHub);

Can someone tell me what to do next?

Answer 1

First add the eventhub, and then  register the listener for this event. Something like this.

        BlockListener blockListener = new BlockListener() {         
        @Override
        public void received(BlockEvent arg0) {
            Block block = arg0.getBlock();

            System.out.println("BLock All FIelds :" + block.getAllFields());
            System.out.println("BLock Number :" + arg0.getBlockNumber());               

            System.out.println("THis is buyer Listener..");
        }
    };

    channel.registerBlockListener(blockListener);\

Comments

But is an (explicitly registered) Event Hub  needed in this case?

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Yes, I think it is necessary to listen to the blocks.

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I have running code that does not register Event Hubs and I still get Block & Chain Code events.

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Hello @Curious. I don't think explicitly registered Event Hub is needed. You can listen to blocks even without that.

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How are you running code without register Event Hubs? Because I tried to do that but it did not work.

Answer 2

I got this from the official documentation:

The following example will register a block listener to start receiving new blocks as they are added to the ledger.

// keep the block_reg to unregister with later if needed
block_reg = channel_event_hub.registerBlockEvent((block) => {
    console.log('Successfully received the block event');
    <do something with the block>
}, (error)=> {
    console.log('Failed to receive the block event ::'+error);
    <do something with the error>
});