Netty提供了应用启动的配置跟启动API，服务端：ServerBootstarp，客户端Bootstarp。

他们用来指定

EventLoopGroup

Channel

ChannelOptions

当Channel注册时，调用ChannelHandler

设置Attributes到指定Chanel。

绑定IP跟端口

ServerBootstarp绑定端口使用bind()。Bootstarp连接使用connect()。

关系：

客户端Bootstarp提供了以下方法：

group(..) ： 设置EventLoopGroup，用于服务Channel中I/O操作

channel(..) 、channelFacotry(..) :  指定使用Channel。 NIO/OIO...

localAddress(...) ：设置本地地址，端口

option(...) ： 设置Channel的配置

attr(..) ： 设置Channel的附加属性

handler(..) ： 设置定义的ChannelHandler到ChannelPipeline中

clone() ： 拷贝。

remoteAddress() : 设置远程连接地址，端口

connect() ： 连接远程服务

bind()    ： 绑定本地服务

Bootstarp，bind()创建Channel后，调用connect()，将会建立连接与Channel()绑定。

若直接调用，则创建Channel 与建立的连接绑定。

Bootstrap bootstrap = new Bootstrap(); #1
bootstrap.group(new NioEventLoopGroup()) #2
.channel(NioSocketChannel.class) #3
.handler(new SimpleChannelInboundHandler<ByteBuf>() { #4
@Override
protected void channeRead0(
ChannelHandlerContext channelHandlerContext,
ByteBuf byteBuf) throws Exception {
System.out.println("Reveived data");
byteBuf.clear();
}
});
ChannelFuture future = bootstrap.connect(
new InetSocketAddress("www.manning.com", 80)); #5
future.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture channelFuture)
throws Exception {
if (channelFuture.isSuccess()) {
System.out.println("Connection established");
} else {
System.err.println("Connection attempt failed");
channelFuture.cause().printStackTrace();
}
}
});

注意：使用NioSocketChannel，则要与NioEventLoopGourp结对绑定，否则报错，OIO同理。

服务端ServerBootstrap
group(..) ： 设置EventLoopGroup，用于服务ServerChannel的I/O操作与接收Channels

channel(..)、channelFacotry ： 设置ServerChannel

localAddress(...) ： 设置ServerChannel绑定地址与端口

option(...) ： 设置ServerChannel的配置

childOption(...) ： 设置ServerChannel accept 并创建的 Channel的配置

attr(...)    ： 设置ServerChannel的额外属性

childAttr(...) ： 设置ServerChannel accept 并创建的  Channel的额外属性

handler(...) ： ServerChannel的ChannelHandler，有默认实现，无特别需求不指定

childHandler(...) ： 设置由ServerChanel accpet到创建的Chanel的ChannelHandler,每个ChannelHandler 对应的处理不同客户端I/O

clone()    ： 拷贝

bind(...) ： 绑定并启动服务。返回ChannelFutrue。

ServerBootstrap bootstrap = new ServerBootstrap(); #1
bootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup()) #2
.channel(NioServerSocketChannel.class) #3
.childHandler(new SimpleChannelInboundHandler<ByteBuf>() { #4
@Override
protected void channelRead0(ChannelHandlerContext ctx,
ByteBuf byteBuf) throws Exception {
System.out.println("Reveived data");
byteBuf.clear();
}
});
ChannelFuture future = bootstrap.bind(new InetSocketAddress(8080)); #5
future.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture channelFuture)
throws Exception {
if (channelFuture.isSuccess()) {
System.out.println("Server bound");
} else {
System.err.println("Bound attempt failed");
channelFuture.cause().printStackTrace();
}
}
});

ServerBootstarp内嵌Bootstarp连接，共同EventLoop例子，使用场景，做代理，或服务端需要连接其他服务来获取数据处理。

ServerBootstrap bootstrap = new ServerBootstrap(); #1
bootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup()) #2
.channel(NioServerSocketChannel.class) #3
.childHandler(new SimpleChannelInboundHandler<ByteBuf>() { #4
ChannelFuture connectFuture;
@Override
public void channelActive(ChannelHandlerContext ctx)
throws Exception {
Bootstrap bootstrap = new Bootstrap(); #5
bootstrap.channel(NioSocketChannel.class) #6
.handler(
new SimpleChannelInboundHandler<ByteBuf>() { #7
@Override
protected void channelRead0(
ChannelHandlerContext ctx,
ByteBuf in) throws Exception {
System.out.println("Reveived data");
in.clear();
}
});
bootstrap.group(ctx.channel().eventLoop()); #8
connectFuture = bootstrap.connect(
new InetSocketAddress("www.manning.com", 80)); #9
}
@Override
protected void channelRead0(ChannelHandlerContext
channelHandlerContext, ByteBuf byteBuf) throws Exception {
if (connectFuture.isDone()) {
// do something with the data #10
}
}
});
ChannelFuture future = bootstrap.bind(new InetSocketAddress(8080)); #11
future.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture channelFuture)
throws Exception {
if (channelFuture.isSuccess()) {
System.out.println("Server bound");
} else {
System.err.println("Bound attempt failed");
channelFuture.cause().printStackTrace();
}
}
});

ServerBootstarp 需要支持多种协议。我们需要加入多个ChannelHandler时候，使用继承ChannelInitializer，并实现initChannel方法，便可以把 Channel加入到ChanelPipeline中，并且与EventLoopGroup关联。例子：

ServerBootstrap bootstrap = new ServerBootstrap(); #1
bootstrap.group(new NioEventLoopGroup(), new NioEventLoopGroup()) #2
.channel(NioServerSocketChannel.class) #3
.childHandler(new ChannelInitializerImpl()); #4
ChannelFuture future = bootstrap.bind(new InetSocketAddress(8080)); #5
future.sync();
final class ChannelInitializerImpl extends ChannelInitializer<Channel> {#6
@Override
protected void initChannel(Channel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline(); #7
pipeline.addLast(new HttpClientCodec());
pipeline.addLast(new HttpObjectAggregator(Integer.MAX_VALUE));
}
}

ChannelOptions and attributes

channelOptions 可以设置 Channel的连接超时，keep-alive等

attributes 可以设置一些用户自定义的值。

final AttributeKey<Integer> id = new AttributeKey<Integer>("ID"); #1
Bootstrap bootstrap = new Bootstrap(); #2
bootstrap.group(new NioEventLoopGroup()) #3
.channel(NioSocketChannel.class) #4
.handler(new SimpleChannelInboundHandler<ByteBuf>() #5
@Override
public void channelRegistered(ChannelHandlerContext ctx)
throws Exception {
Integer idValue = ctx.channel().attr(id).get(); #6
// do something with the idValue
}
@Override
protected void channelRead0(
ChannelHandlerContext channelHandlerContext,
ByteBuf byteBuf) throws Exception {
System.out.println("Reveived data");
byteBuf.clear();
}
});
bootstrap.option(ChannelOption.SO_KEEPALIVE,true)
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 5000); #7
bootstrap.attr(id, 123456); #8
ChannelFuture future = bootstrap.connect(
new InetSocketAddress("www.manning.com", 80)); #9
future.syncUninterruptibly();

使用UDP协议，跟Bootstarp有一点不同的是，不需要bind() 或 connect() 操作

Bootstrap bootstrap = new Bootstrap();
bootstrap.group(new OioEventLoopGroup()).channel(OioDatagramChannel.class)
.handler(new SimpleChannelInboundHandler<DatagramPacket>(){
@Override
public void channelRead0(ChannelHandlerContext ctx,
DatagramPacket msg) throws Exception {
// Do something with the packet
}
});
ChannelFuture future = bootstrap.bind(new InetSocketAddress(0));
future.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture channelFuture)
throws Exception {
if (channelFuture.isSuccess()) {
System.out.println("Channel bound");
} else {
System.err.println("Bound attempt failed");
channelFuture.cause().printStackTrace();
}
}
});