whisper 有没有java sdk

Whisper Java SDK: A Comprehensive Guide

Introduction

Whisper is a decentralized messaging protocol that allows users to send and receive messages securely and privately. It is built on top of the Ethereum blockchain and utilizes its peer-to-peer network for message transmission.

In this article, we will explore whether Whisper has a Java Software Development Kit (SDK) available and provide a code example to demonstrate its usage.

Whisper Java SDK

Whisper does not have an official Java SDK provided by the Ethereum Foundation. However, there are community-developed libraries and wrappers that can be used to interact with Whisper in a Java environment.

One such library is the web3j library. web3j is a lightweight, highly modular, reactive Java and Android library for working with Ethereum. It provides a convenient way to interact with various Ethereum components, including Whisper.

To use web3j for Whisper messaging, you need to add the following dependency to your pom.xml file:

<dependency>
    <groupId>org.web3j</groupId>
    <artifactId>core</artifactId>
    <version>4.8.6</version>
</dependency>

Once you have added the dependency, you can use the web3j library to send and receive Whisper messages.

Sending a Whisper Message

To send a Whisper message, you need to create an instance of the Whisper class from the web3j library. The Whisper class provides methods to send and subscribe to Whisper messages.

Here is an example code snippet to send a Whisper message using web3j:

import org.web3j.protocol.Web3j;
import org.web3j.protocol.http.HttpService;
import org.web3j.protocol.parity.Parity;
import org.web3j.protocol.parity.methods.response.ShhPost;
import org.web3j.protocol.parity.methods.response.ShhVersion;
import org.web3j.utils.Async;

public class WhisperExample {
    public static void main(String[] args) {
        Web3j web3j = Web3j.build(new HttpService(http://localhost:8545));
        Parity parity = Parity.build(new HttpService(http://localhost:8545));

        try {
            ShhVersion version = web3j.shhVersion().send();
            System.out.println(Whisper version:  + version.getResult());

            ShhPost whisperPost = parity.shhPost(
                    new org.web3j.protocol.parity.methods.request.ShhPost(
                            Hello, Whisper!,
                            0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef,
                            0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
                    )
            ).sendAsync().get();

            String messageHash = whisperPost.getResult();
            System.out.println(Message sent! Hash:  + messageHash);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

In the above code, we first create instances of Web3j and Parity by providing the URL of the Ethereum node. Then, we use the shhVersion() method to retrieve the Whisper version. After that, we use the shhPost() method to send a Whisper message asynchronously.

Receiving a Whisper Message

To receive Whisper messages, you need to subscribe to the Whisper topic you are interested in. Only messages sent to the subscribed topic will be received.

Here is an example code snippet to receive Whisper messages using web3j:

import org.web3j.protocol.Web3j;
import org.web3j.protocol.http.HttpService;
import org.web3j.protocol.parity.Parity;
import org.web3j.protocol.parity.methods.response.ShhMessages;
import org.web3j.protocol.parity.methods.response.ShhNewMessage;
import org.web3j.utils.Async;

public class WhisperExample {
    public static void main(String[] args) {
        Web3j web3j = Web3j.build(new HttpService(http://localhost:8545));
        Parity parity = Parity.build(new HttpService(http://localhost:8545));

        try {
            ShhVersion version = web3j.shhVersion().send();
            System.out.println(Whisper version:  + version.getResult());

            ShhNewMessage newMessage = parity.shhNewMessageFilter(
                    new org.web3j.protocol.parity.methods.request.ShhFilter(
                            0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
                    )
            ).sendAsync().get();

            ShhMessages messages = parity.shhGetFilterMessages(newMessage.getFilterId()).send();

            for (ShhMessages.SshMessage message : messages.getResult()) {
                System.out.println(Received message:  + message.getPayload());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

In the above code, we again create instances of Web3j and Parity. We use the shhVersion() method to retrieve the Whisper version. Then, we use the shhNewMessageFilter() method to create a filter for receiving messages. Finally, we