netty 学习 （3）发送对象
Netty中，通讯的双方建立连接后，会把数据按照ByteBuf的方式进行传输，例如http协议中，就是通过HttpRequestDecoder对ByteBuf数据流进行处理，转换成http的对象。基于这个思路，我自定义一种通讯协议：Server和客户端直接传输java对象。
实现的原理是通过Encoder把java对象转换成ByteBuf流进行传输，通过Decoder把ByteBuf转换成java对象进行处理，处理逻辑如下图所示：
使用的jar包：
使用的log4j.xml文件：
<?xml version="1.0"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="[%-5p] [%d] [%t] [%c] %m%n"/>
</layout>
</appender>
<appender name="FILE" class="org.apache.log4j.DailyRollingFileAppender">
<param name="File" value="./log/netty.log"/>
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="[%-5p] [%d] [%t] [%c] %m%n"/>
</layout>
</appender>
<appender name="FILE_ERR" class="org.apache.log4j.DailyRollingFileAppender">
<param name="File" value="./log/netty_err.log"/>
<param name="Threshold" value="ERROR" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="[%-5p] [%d] [%t] [%c] %m%n"/>
</layout>
</appender>
<logger name="io.netty" additivity="false">
<level value="INFO,DEBUG" />
<appender-ref ref="FILE" />
<appender-ref ref="FILE_ERR" />
<appender-ref ref="CONSOLE" />
</logger>
<logger name="com.yao" additivity="false">
<level value="INFO,DEBUG" />
<appender-ref ref="FILE" />
<appender-ref ref="FILE_ERR" />
<appender-ref ref="CONSOLE" />
</logger>
<root>
<level value="debug"/>
<appender-ref ref="FILE"/>
<appender-ref ref="CONSOLE"/>
<appender-ref ref="FILE_ERR" />
</root>
</log4j:configuration>
传输的java bean为Person：
package com.yao.nettyobject;
import java.io.Serializable;
// 必须实现Serializable接口
public class Person implements Serializable{
private static final long serialVersionUID = 1L;
private String name;
private String sex;
private int age;
public String toString() {
return "name:" + name + " sex:" + sex + " age:" + age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
Server端类：Server PersonDecoder BusinessHandler
1、Server：启动netty服务
package com.yao.nettyobject;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
public class Server {
public void start(int port) throws Exception {
EventLoopGroup bossGroup = new NioEventLoopGroup();
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
//解码
ch.pipeline().addLast(new PersonDecoder());
//业务处理
ch.pipeline().addLast(new BusinessHandler());
}
}).option(ChannelOption.SO_BACKLOG, 128)
.childOption(ChannelOption.SO_KEEPALIVE, true);
ChannelFuture f = b.bind(port).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
bossGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
Server server = new Server();
server.start(8000);
}
}
2、PersonDecoder：把ByteBuf流转换成Person对象，其中ByteBufToBytes是读取ButeBuf的工具类，上一篇文章中提到过，在此不在详述。ByteObjConverter是byte和obj的互相转换的工具。
package com.yao.nettyobject;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
import java.util.List;
public class PersonDecoder extends ByteToMessageDecoder {
@Override
protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception {
ByteBufToBytes read = new ByteBufToBytes();
Object obj = ByteObjConverter.byteToObject(read.read(in));
out.add(obj);
}
}
package com.yao.nettyobject;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class BusinessHandler extends ChannelInboundHandlerAdapter {
private Log logger = LogFactory.getLog(BusinessHandler.class);
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
Person person = (Person) msg;
logger.info("BusinessHandler read msg from client :" + person);
}
@Override
public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
ctx.flush();
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
}
}
Client端的类：Client ClientInitHandler PersonEncoder
1、Client 建立与Server的连接
package com.yao.nettyobject;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
public class Client {
public void connect(String host, int port) throws Exception {
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(workerGroup);
b.channel(NioSocketChannel.class);
b.option(ChannelOption.SO_KEEPALIVE, true);
b.handler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
//编码
ch.pipeline().addLast(new PersonEncoder());
//
ch.pipeline().addLast(new ClientInitHandler());
}
});
ChannelFuture f = b.connect(host, port).sync();
f.channel().closeFuture().sync();
} finally {
workerGroup.shutdownGracefully();
}
}
public static void main(String[] args) throws Exception {
Client client = new Client();
client.connect("127.0.0.1", 8000);
}
}
package com.yao.nettyobject;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
public class ClientInitHandler extends ChannelInboundHandlerAdapter {
private static Log logger = LogFactory.getLog(ClientInitHandler.class);
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
logger.info("HelloClientIntHandler.channelActive");
Person person = new Person();
person.setName("yaokj");
person.setSex("man");
person.setAge(30);
ctx.write(person);
ctx.flush();
}
}
package com.yao.nettyobject;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToByteEncoder;
public class PersonEncoder extends MessageToByteEncoder<Person> {
@Override
protected void encode(ChannelHandlerContext ctx, Person msg, ByteBuf out) throws Exception {
byte[] datas = ByteObjConverter.objectToByte(msg);
out.writeBytes(datas);
ctx.flush();
}
}
package com.yao.nettyobject;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
public class ByteObjConverter {
public static Object byteToObject(byte[] bytes) {
Object obj = null;
ByteArrayInputStream bi = new ByteArrayInputStream(bytes);
ObjectInputStream oi = null;
try {
oi = new ObjectInputStream(bi);
obj = oi.readObject();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
bi.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
oi.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return obj;
}
public static byte[] objectToByte(Object obj) {
byte[] bytes = null;
ByteArrayOutputStream bo = new ByteArrayOutputStream();
ObjectOutputStream oo = null;
try {
oo = new ObjectOutputStream(bo);
oo.writeObject(obj);
bytes = bo.toByteArray();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
bo.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
oo.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return bytes;
}
}
package com.yao.nettyobject;
import io.netty.buffer.ByteBuf;
public class ByteBufToBytes {
public byte[] read(ByteBuf datas) {
byte[] bytes = new byte[datas.readableBytes()];
datas.readBytes(bytes);
return bytes;
}
}
通过上述代码，实现了Server端与Client端直接使用person对象进行通信的目的。基于此，可以构建更为复杂的场景：Server端同时支撑多种协议，不同的协议采用不同的Decoder进行解析，解析结果保持统一，这样业务处理类可以保持接口一致。下一节将编写这样一个案例。
本例中需要注意的事项是：
1、Person对象必须实现Serializable接口，否则不能进行序列化。
2、PersonDecoder读取ByteBuf数据的时候，并没有对多次流式数据进行处理，而是简单的一次性接收，如果数据量大的情况下，可能会出现数据不完整，这个问题会在后续的学习中解决。