netty传输java bean对象
在上一篇博客(netty入门实现简单的echo程序)中,我们知道了如何使用netty发送一个简单的消息,但是这远远是不够的。在这篇博客中,我们来使用netty发送一个java bean对象的消息,但是要发送对象类型的消息,必然要将java对象进行序列化,在java中序列化框架有很多中,此处我们使用protostuff来进行序列化,不了解protostuff的可以先看一下这篇博客(protostuff序列化)了解一下简单的用法。
需求:
客户端在连接上服务器端时,向服务器发送100个Person对象。
服务器端接收到消息后在控制台上打印即可。
消息发送的协议:4个字节的长度(长度是后面对象的长度,不包含自身的4个字节),后面是实际的要发送的数据
实现思路:
一、服务器端:
1、服务器端先用LengthFieldBasedFrameDecoder进行解码,获取到一个完整的ByteBuf消息
2、然后编写ProtostuffDecoder解码器将上一步解码出来的消息,转换成一个Person对象
3、编写ProtoStuffServerHandler类用于将上一步解码出来的Person对象输出出来
二、客户端
1、编写ProtostuffClientHandler类用于向服务器端发送Person对象
2、编写ProtostuffEncoder来进行将Person对象转换成字节数组
3、借助netty的LengthFieldPrepender来向上一步的字节数组前增加4个字节的消息长度
半包的处理主要是借助netty提交的LengthFieldBasedFrameDecoder来进行处理
注意:
new LengthFieldPrepender(4) ==> 会在发送的数据前增加4个字节表示消息的长度
new LengthFieldBasedFrameDecoder(10240, 0, 4, 0, 4) ==> 10240表示如果此次读取的字节长度比这个大说明可能是别人伪造socket攻击,将会抛出异常,第一个4表示读取四个字节表示此次 消息的长度,后面一个4表示丢弃四个字节,然后读取业务数据。
实现步骤:
一、引入maven依赖
<strong><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.huan.netty</groupId>
<artifactId>netty-study</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>netty-study</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.6.Final</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.18</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.1.7</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.1.7</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-access</artifactId>
<version>1.1.7</version>
</dependency>
<dependency>
<groupId>io.protostuff</groupId>
<artifactId>protostuff-api</artifactId>
</dependency>
<dependency>
<groupId>io.protostuff</groupId>
<artifactId>protostuff-core</artifactId>
</dependency>
<dependency>
<groupId>io.protostuff</groupId>
<artifactId>protostuff-runtime</artifactId>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>io.protostuff</groupId>
<artifactId>protostuff-bom</artifactId>
<version>1.4.4</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>
</strong>
二、编写实体类Person(客户端将会发送这个对象,服务器端接收这个对象)
<strong>@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Person {
private int id;
private String name;
}</strong>
三、编写ProtostuffDecoder用将ByteBuf中的数据转换成Person对象
<strong>public class ProtostuffDecoder extends ByteToMessageDecoder {
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
Schema<Person> schema = RuntimeSchema.getSchema(Person.class);
Person person = schema.newMessage();
byte[] array = new byte[in.readableBytes()];
in.readBytes(array);
ProtobufIOUtil.mergeFrom(array, person, schema);
out.add(person);
}
}</strong>
四、编写ProtoStuffServerHandler用于将接收到的数据输出到控制台
<strong>@Slf4j
public class ProtoStuffServerHandler extends ChannelInboundHandlerAdapter {
private int counter = 0;
/**
* 接收到数据的时候调用
*/
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
Person person = (Person) msg;
log.info("当前是第[{}]次获取到客户端发送过来的person对象[{}].", ++counter, person);
}
/** 当发生了异常时,次方法调用 */
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
log.error("error:", cause);
ctx.close();
}
}
</strong>
五、编写netty的服务端,用于启动netty的服务
<strong>@Slf4j
public class NettyServer {
public static void main(String[] args) throws Exception {
EventLoopGroup boss = new NioEventLoopGroup(1);
EventLoopGroup worker = new NioEventLoopGroup();
ServerBootstrap bootstrap = new ServerBootstrap();
bootstrap.group(boss, worker)//
.channel(NioServerSocketChannel.class)// 对应的是ServerSocketChannel类
.option(ChannelOption.SO_BACKLOG, 128)//
.handler(new LoggingHandler(LogLevel.TRACE))//
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new LengthFieldBasedFrameDecoder(10240, 0, 4, 0, 4));
ch.pipeline().addLast(new ProtostuffDecoder());
ch.pipeline().addLast(new ProtoStuffServerHandler());
}
});
ChannelFuture future = bootstrap.bind(9090).sync();
log.info("server start in port:[{}]", 9090);
future.channel().closeFuture().sync();
boss.shutdownGracefully();
worker.shutdownGracefully();
}
}</strong>
此处需要注意解码器的顺序:
必须要先是LengthFieldBasedFrameDecoder,然后是ProtostuffDecoder,在是ProtoStuffServerHandler
六、编写客户端的handler处理器,用于向服务器端发送Person对象
<strong>@Slf4j
public class ProtostuffClientHandler extends ChannelInboundHandlerAdapter {
/**
* 客户端和服务器端TCP链路建立成功后,此方法被调用
*/
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
Person person;
for (int i = 0; i < 100; i++) {
person = new Person();
person.setId(i);
person.setName("张三" + i);
ctx.writeAndFlush(person);
}
}
/**
* 发生异常时调用
*/
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
log.error("client error:", cause);
ctx.close();
}
}</strong>
七、编写ProtostuffEncoder编码器,用于将Person对象编码成字节数组
<strong>public class ProtostuffEncoder extends MessageToByteEncoder<Person> {
@Override
protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception {
LinkedBuffer buffer = LinkedBuffer.allocate(1024);
Schema<Person> schema = RuntimeSchema.getSchema(Person.class);
byte[] array = ProtobufIOUtil.toByteArray(msg, schema, buffer);
out.writeBytes(array);
}
}</strong>
八、编写客户端
<strong>@Slf4j
public class NettyClient {
public static void main(String[] args) throws InterruptedException {
EventLoopGroup group = new NioEventLoopGroup();
Bootstrap bootstrap = new Bootstrap();
bootstrap.group(group)//
.channel(NioSocketChannel.class)//
.option(ChannelOption.TCP_NODELAY, true)//
.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel ch) throws Exception {
ch.pipeline().addLast(new LengthFieldPrepender(4));
ch.pipeline().addLast(new ProtostuffEncoder());
ch.pipeline().addLast(new ProtostuffClientHandler());
}
});
ChannelFuture future = bootstrap.connect("127.0.0.1", 9090).sync();
log.info("client connect server.");
future.channel().closeFuture().sync();
group.shutdownGracefully();
}
}
</strong>
注意:此处也需要注意initChannel方法中的编码器加入的顺序
ProtostuffEncoder->将Person对象转换成字节数组
LengthFieldPrepender->在上一步的字节数组前加入4个字节的长度
九、启动服务器端和客户端进行测试
本文来自博客园,作者:huan1993,转载请注明原文链接:https://www.cnblogs.com/huan1993/p/15416201.html