netty對多協議進行編解碼-有解無憂

1、netty如何決議多協議

前提：

專案地址：https://gitee.com/q529075990qqcom/NB-IOT.git

我們需要一個創建mavne專案，這個專案是我已經寫好的專案，專案結構圖如下：

創建公共模塊

創建子模塊，準備好依賴Netty4.1版本

<dependencies>
    <dependency>
      <groupId>io.netty</groupId>
      <artifactId>netty-all</artifactId>
      <version>4.1.72.Final</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.28</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-simple</artifactId>
      <version>1.7.28</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>com.esotericsoftware</groupId>
      <artifactId>kryo</artifactId>
      <version>5.3.0</version>
    </dependency>
  </dependencies>

maven依賴

序列化的定義是：將一個物件編碼成一個位元組流（I/O）；而與之相反的操作被稱為反序列化，

package serializer;

/**
 * @description:
 * @author: quliang
 * @create: 2022-10-20 15:16
 **/
public interface Serializer {
    /**
     * 序列化
     *
     * @param obj
     * @return
     * @throws Exception
     */
    byte[] serialize(Object obj) throws Exception;

    /**
     * 反序列化
     *
     * @param bytes
     * @param clazz
     * @param <T>
     * @return
     * @throws Exception
     */
    <T> T deserialize(byte[] bytes, Class<T> clazz) throws Exception;

}

自定義序列化介面

package serializer;

import com.esotericsoftware.kryo.Kryo;
import com.esotericsoftware.kryo.io.Input;
import com.esotericsoftware.kryo.io.Output;
import com.esotericsoftware.kryo.util.DefaultInstantiatorStrategy;
import org.objenesis.strategy.StdInstantiatorStrategy;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

/**
 * @description:
 * @author: quliang
 * @create: 2022-10-20 15:18
 **/

public class KryoSerializer implements Serializer {
    private static final ThreadLocal<Kryo> kryoThreadLocal = ThreadLocal.withInitial(() -> {
        Kryo kryo = new Kryo();
        kryo.setReferences(true);
        kryo.setRegistrationRequired(false);
        ((DefaultInstantiatorStrategy) kryo.getInstantiatorStrategy())
                .setFallbackInstantiatorStrategy(new StdInstantiatorStrategy());
        return kryo;
    });

    @Override
    public byte[] serialize(Object obj) throws Exception {
        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
            Output output = new Output(baos);
            Kryo kryo = kryoThreadLocal.get();
            kryo.writeObject(output, obj);
            kryoThreadLocal.remove();
            return output.toBytes();
        } catch (IOException e) {
            throw new Exception("序列化失敗", e);
        }
    }

    @Override
    public <T> T deserialize(byte[] bytes, Class<T> clazz) throws Exception {
        try (ByteArrayInputStream bais = new ByteArrayInputStream(bytes)) {
            Input input = new Input(bais);
            Kryo kryo = kryoThreadLocal.get();
            Object obj = kryo.readObject(input, clazz);
            kryoThreadLocal.remove();
            return clazz.cast(obj);
        } catch (IOException e) {
            throw new Exception("反序化失敗");
        }
    }
}

Kryo實作序列化介面

我們需要決議兩種協議，那我們就要提前定義好兩種協議，分別是訊息協議、登錄協議

訊息協議相關

package protocol.msg;

import lombok.Data;
import lombok.Getter;

/**
 * @description: 訊息協議： |magic|version|data|
 * @author: quliang
 * @create: 2022-12-10 20:46
 **/
@Data
public class MsgProtocol {
    @Getter
    private byte magic=0;
    @Getter
    private byte version=1;
}

訊息協議基類

package protocol.msg.request;

import lombok.Data;
import protocol.msg.MsgProtocol;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-10 20:58
 **/
@Data
public class MsgRequest extends MsgProtocol {
    private String msg;
}

訊息請求子類

package protocol.msg.response;

import lombok.Data;
import protocol.msg.MsgProtocol;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-10 20:41
 **/
@Data
public class MsgResponse extends MsgProtocol {
    private int statCode;
}

訊息回應子類

package encoder;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import protocol.msg.MsgProtocol;
import serializer.KryoSerializer;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-10 20:53
 **/

public class MsgEncoder extends MessageToByteEncoder<MsgProtocol> {

    @Override
    protected void encode(ChannelHandlerContext ctx, MsgProtocol msgProtocol, ByteBuf in) throws Exception {
        in.writeByte(msgProtocol.getMagic());
//        in.writeByte(msgProtocol.code());
        in.writeByte(msgProtocol.getVersion());
        byte[] data = https://www.cnblogs.com/quliang/p/new KryoSerializer().serialize(msgProtocol);
        in.writeShort(data.length);
        in.writeBytes(data);
    }
}

訊息協議編碼

package decoder;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import lombok.extern.slf4j.Slf4j;
import protocol.msg.MsgProtocol;
import serializer.KryoSerializer;

import java.util.List;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-10 20:52
 **/
@Slf4j
public class MsgDecoder extends ByteToMessageDecoder {

    private Class<MsgProtocol> msgClass;

    public MsgDecoder(Class clazz) {
        this.msgClass = clazz;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        try {
            byte magic = in.readByte();
            byte version = in.readByte();

            short dataSize = in.readShort();
            byte[] data = https://www.cnblogs.com/quliang/p/new byte[dataSize];
            in.readBytes(data);

            MsgProtocol baseProtocol = new KryoSerializer().deserialize(data, msgClass);
            out.add(baseProtocol);
        } catch (Exception e) {
            //如果解碼錯誤，將資料傳遞到下一個解碼器中
            log.error("msg decoder {}",e.getMessage());
            // 重置讀取位元組索引，因為上邊已經讀了（readBytes），不加這個會導致資料為空
            in.resetReaderIndex();
            // 這里是復制流，復制一份，防止skipBytes跳過，導致傳遞的訊息變成空；
            ByteBuf buff = in.retainedDuplicate();
            //原因是netty不允許有位元組內容不讀的情況發生，所以采用下邊的方法解決，
            in.skipBytes(in.readableBytes());
            //繼續傳遞到下一個解碼器中
            out.add(buff);
        }
    }
}

訊息協議解碼

登錄協議相關

package protocol.system;



import lombok.Getter;

/**
 * @description: 登錄協議： |magic|version|code|data|
 * @author: quliang
 * @create: 2022-12-09 18:10
 **/

public class LoginProtocol {
    @Getter
    private byte magic=0;
    @Getter
    private byte version=1;
    @Getter
    public byte code;
}

登錄協議基類

package protocol.system.request;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import protocol.system.LoginProtocol;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-06 18:17
 **/
@Data
@NoArgsConstructor
@AllArgsConstructor
public class LoginRequest extends LoginProtocol {

    private String userId;

    private String userName;
}

登錄請求子類

package protocol.system.response;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import protocol.system.LoginProtocol;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-06 18:22
 **/
@Data
@NoArgsConstructor
@AllArgsConstructor
public class LoginResponse extends LoginProtocol {

    private String msg;

    private String data;

}

登錄回應子類

package encoder;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
import protocol.system.LoginProtocol;
import serializer.KryoSerializer;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-06 22:11
 **/

public class LoginEncoder extends MessageToByteEncoder<LoginProtocol> {

    @Override
    protected void encode(ChannelHandlerContext ctx, LoginProtocol baseProtocol, ByteBuf in) throws Exception {
        in.writeByte(baseProtocol.getMagic());
        in.writeByte(baseProtocol.getCode());
        in.writeByte(baseProtocol.getVersion());
        byte[] data = https://www.cnblogs.com/quliang/p/new KryoSerializer().serialize(baseProtocol);
        in.writeShort(data.length);
        in.writeBytes(data);
    }
}

登錄協議編碼

package decoder;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import lombok.extern.slf4j.Slf4j;
import protocol.system.LoginProtocol;
import serializer.KryoSerializer;
import java.util.List;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-06 17:59
 **/
@Slf4j
public class LoginDecoder extends ByteToMessageDecoder {

    private Class<LoginProtocol> clazz;

    public LoginDecoder(Class clazz) {
        this.clazz = clazz;
    }

    @Override
    protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
        try {
            byte magic = in.readByte();
            byte code = in.readByte();
            byte version = in.readByte();

            short dataSize = in.readShort();
            byte[] data = https://www.cnblogs.com/quliang/p/new byte[dataSize];
            in.readBytes(data);

            LoginProtocol baseProtocol = new KryoSerializer().deserialize(data, clazz);
            out.add(baseProtocol);
        } catch (Exception e) {
            //如果解碼錯誤，將資料傳遞到下一個解碼器中
            log.error("login decoder {}", e.getMessage());
            // 重置讀取位元組索引，因為上邊已經讀了（readBytes），不加這個會導致資料為空
            in.resetReaderIndex();
            // 這里是復制流，復制一份，防止skipBytes跳過，導致傳遞的訊息變成空；
            ByteBuf buff = in.retainedDuplicate();
            //原因是netty不允許有位元組內容不讀的情況發生，所以采用下邊的方法解決，
            in.skipBytes(in.readableBytes());
            //繼續傳遞到下一個解碼器中
            out.add(buff);
        }
    }
}

登錄協議解碼

這樣公共模塊就創建完成了

創建服務端

package com.ql;

import com.ql.handler.MsgHandler;
import decoder.LoginDecoder;
import decoder.MsgDecoder;
import com.ql.handler.LoginHandler;
import encoder.LoginEncoder;
import encoder.MsgEncoder;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;
import protocol.system.request.LoginRequest;
import protocol.msg.request.MsgRequest;

/**
 * @author quliang
 * @description 服務端
 * @date 2022-12-06 17:39:14
 */
@Slf4j
public class IotServer {

    public static void main(String[] args) throws InterruptedException {
        NioEventLoopGroup bossGroup = new NioEventLoopGroup();
        NioEventLoopGroup workGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap().group(
                    bossGroup, workGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel channel) throws Exception {
                            ChannelPipeline pipeline = channel.pipeline();
                            pipeline.addLast(new LoggingHandler(LogLevel.INFO));
                            /**
                             * 心跳機制
                             */
                            //pipeline.addLast(new IdleStateHandler(5, 10, 5, TimeUnit.SECONDS));

                            /**
                             * 訊息、登錄解碼器
                             */
                            pipeline.addLast(new LoginDecoder(LoginRequest.class));
                            pipeline.addLast(new MsgDecoder(MsgRequest.class));

                            /**
                             * 訊息、登錄處理器
                             */
                            pipeline.addLast(new MsgHandler());
                            pipeline.addLast(new LoginHandler());

                            /**
                             * 訊息、登錄編碼器
                             */
                            pipeline.addLast(new MsgEncoder());
                            pipeline.addLast(new LoginEncoder());

                        }
                    })
                    .option(ChannelOption.SO_BACKLOG, 1024);

            ChannelFuture cf = bootstrap.bind(8849).sync();
            log.info("socket服務端啟動成功 {}", cf.channel().localAddress().toString());

            cf.channel().closeFuture().sync();
        } finally {
            bossGroup.shutdownGracefully();
            workGroup.shutdownGracefully();
        }

    }
}

服務端代碼

package com.ql.handler;

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;
import protocol.msg.request.MsgRequest;
import protocol.msg.response.MsgResponse;

/**
 * @description: 訊息處理器
 * @author: quliang
 * @create: 2022-12-10 20:57
 **/
@Slf4j
@ChannelHandler.Sharable
public class MsgHandler extends SimpleChannelInboundHandler<MsgRequest> {
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        log.info("上線{}", ctx.channel().remoteAddress().toString());
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MsgRequest request) throws Exception {
        log.info("服務端讀取訊息體資料為{}", request.toString());
        MsgResponse response = new MsgResponse();
        response.setStatCode(200);
        ctx.channel().writeAndFlush(response);
    }
}

服務端訊息處理器

package com.ql.handler;

import io.netty.channel.*;
import io.netty.handler.timeout.IdleStateEvent;
import lombok.extern.slf4j.Slf4j;
import protocol.system.request.LoginRequest;
import protocol.system.response.LoginResponse;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * @description: 登錄處理器
 * @author: quliang
 * @create: 2022-12-06 18:14
 **/
@Slf4j
@ChannelHandler.Sharable
public class LoginHandler extends SimpleChannelInboundHandler<LoginRequest>{
    private static AtomicInteger READER_COUNT = new AtomicInteger(0);

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        log.info("服務端：{} 通道開啟！", ctx.channel().localAddress().toString());
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        log.info("服務端: {} 通道關閉！", ctx.channel().localAddress().toString());
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoginRequest loginRequest) throws Exception {
        log.info("讀取資料 {} ", loginRequest.toString());
        LoginResponse response= new LoginResponse("success", null);
        ctx.channel().writeAndFlush(response);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        log.info("...............資料接收-完畢...............");
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        ctx.close();
        log.error("...............業務處理例外...............{}", cause);
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        if (evt instanceof IdleStateEvent) {
            IdleStateEvent event = (IdleStateEvent) evt;
            Channel channel = ctx.channel();
            switch (event.state()) {
                case READER_IDLE:
                    log.info("讀空閑");
                    READER_COUNT.addAndGet(1);
                    break;
                case WRITER_IDLE:
                    log.info("寫空閑");
                    break;
                default:
                    break;
            }
            ctx.disconnect();
            if (READER_COUNT.get() > 3) {
                log.info("close this channel {}", channel.remoteAddress().toString());
            }
        }
    }

}

服務端登錄處理器

服務端其實很多都是直接參考公共模塊的，代碼也并不復雜

創建訊息客戶端

package com.ql;

import com.ql.handler.ClientMsgHandler;
import decoder.MsgDecoder;
import encoder.MsgEncoder;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;
import protocol.msg.response.MsgResponse;

import java.net.InetSocketAddress;

/**
 * @author quliang
 * @description 客戶端
 * @date 2022-12-06 17:37:56
 */
@Slf4j
public class IotClientMsg {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup clientGroup = new NioEventLoopGroup();
        try {
            Bootstrap bs = new Bootstrap();
            bs.group(clientGroup)
                    .channel(NioSocketChannel.class)
                    .remoteAddress(new InetSocketAddress("169.254.190.154", 8849))
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new LoggingHandler(LogLevel.INFO));

                            //訊息解碼器
                            pipeline.addLast(new MsgDecoder(MsgResponse.class));
                            //客戶端訊息處理器
                            pipeline.addLast(new ClientMsgHandler());
                            //訊息編碼器
                            pipeline.addLast(new MsgEncoder());
                        }
                    });

            ChannelFuture cf = bs.connect().sync();
            log.info("啟動成功{}", cf.channel().localAddress().toString());

//            Scanner scanner = new Scanner(System.in);

            cf.channel().closeFuture().sync();
        } finally {
            clientGroup.shutdownGracefully().sync();
        }
    }
}

客戶端代碼

package com.ql.handler;

import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import lombok.extern.slf4j.Slf4j;
import protocol.msg.request.MsgRequest;
import protocol.msg.response.MsgResponse;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-10 20:40
 **/
@Slf4j
@ChannelHandler.Sharable
public class ClientMsgHandler extends SimpleChannelInboundHandler<MsgResponse> {

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        MsgRequest request = new MsgRequest();
        request.setMsg("hello");
        ctx.channel().writeAndFlush(request);
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, MsgResponse response) throws Exception {
        int code = response.getStatCode();
        log.info("訊息處理器讀取回應物件資料為{}", code);
    }
}

客戶端訊息處理器

訊息客戶端代碼也并不復雜

創建登錄客戶端

package com.ql;

import com.ql.handler.ClientLoginHandler;
import decoder.LoginDecoder;
import encoder.LoginEncoder;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
import lombok.extern.slf4j.Slf4j;
import protocol.system.response.LoginResponse;

import java.net.InetSocketAddress;

/**
 * @author quliang
 * @description 客戶端
 * @date 2022-12-06 17:37:56
 */
@Slf4j
public class IotClientLogin {
    public static void main(String[] args) throws InterruptedException {
        EventLoopGroup clientGroup = new NioEventLoopGroup();
        try {
            Bootstrap bs = new Bootstrap();
            bs.group(clientGroup)
                    .channel(NioSocketChannel.class)
                    .remoteAddress(new InetSocketAddress("169.254.190.154", 8849))
                    .handler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        protected void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline pipeline = ch.pipeline();
                            pipeline.addLast(new LoggingHandler(LogLevel.INFO));

                            pipeline.addLast(new LoginDecoder(LoginResponse.class));
                            //pipeline.addLast(new MsgDecoder(MsgResponse.class));

                            //pipeline.addLast(new ClientMsgHandler());
                            pipeline.addLast(new ClientLoginHandler());

                            //pipeline.addLast(new MsgEncoder());
                            pipeline.addLast(new LoginEncoder());
                        }
                    });

            ChannelFuture cf = bs.connect().sync();
            log.info("啟動成功{}", cf.channel().localAddress().toString());

//            Scanner scanner = new Scanner(System.in);

            cf.channel().closeFuture().sync();
        } finally {
            clientGroup.shutdownGracefully().sync();
        }
    }
}

客戶端代碼

package com.ql.handler;

import io.netty.channel.*;
import lombok.extern.slf4j.Slf4j;
import protocol.system.request.LoginRequest;
import protocol.system.response.LoginResponse;

import java.util.Scanner;

/**
 * @description:
 * @author: quliang
 * @create: 2022-12-06 22:16
 **/
@Slf4j
@ChannelHandler.Sharable
public class ClientLoginHandler extends SimpleChannelInboundHandler<LoginResponse>  {

    private Scanner scanner = new Scanner(System.in);

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        log.info("客戶端：{} 通道開啟！", ctx.channel().localAddress().toString());
        login(ctx);
    }

    /**
     * 登錄方法
     * @param ctx
     */
    private void login(ChannelHandlerContext ctx) {
        LoginRequest request = new LoginRequest("123", "123");
        ctx.channel().writeAndFlush(request);
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        log.info("客戶端: {} 讀取資料 {}", ctx.channel().localAddress().toString(), msg.toString());
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoginResponse response) throws Exception {
        log.info("客戶端: {} 讀取資料 {}", ctx.channel().localAddress().toString(), response.toString());
        String msg = response.getMsg();
        log.info("========{}", msg);
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        log.info("...............資料接收-完畢...............");
    }
}

客戶端登錄處理器

我們是怎么通過這個專案來實作不同協議編解碼？

其實也不難，我們仔細看MsgDecoder、LoginDecoder兩個類其中一個類的代碼，其中有個巧妙的操作就是使用try-catch，

只要解碼器無法解碼發生例外，就重置讀取位元組索引傳遞到下一個解碼器中，直到傳遞到正確解碼器中，不過為了兼容多種協議，

解碼例外也會讓服務端性能有所下降的，取舍之間必有得失，

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標籤：Java

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