netty支持SSL，OpenSSL

import io.netty.channel.Channel;
import io.netty.channel.ChannelInitializer;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslHandler;

import javax.net.ssl.SSLEngine;

public class SslChannelInitializer extends ChannelInitializer<Channel> {
    private final SslContext context;
    private final boolean startTls;
    // context:传入要使用的SslContext
    // startTls:如果设置为true，第一个写入的消息将不会被加密（客户端应该设置为true）
    public SslChannelInitializer(SslContext context,boolean startTls) { 
        this.context = context;
        this.startTls = startTls;
    }

    @Override
    protected void initChannel(Channel ch) throws Exception {
        //对于每个SslHandler 实例，都使用Channel 的ByteBufAllocator 从SslContext 获取一个新的SSLEngine
        SSLEngine engine = context.newEngine(ch.alloc());
        //将SslHandler作为第一个ChannelHandler添加到ChannelPipeline 中
        ch.pipeline().addFirst("ssl",new SslHandler(engine, startTls));   
    }
}