Netty框架 - 引导类Bootstrap

r囧r小猫 2023-07-14 10:57 7阅读 0赞

### Netty框架 - 引导类Bootstrap ###

*  Bootstrap引导类
 *   *  Bootstrap继承结构
 *  Bootstrap常用功能
 *   *  1、设置EventLoopGroup线程池
     *  2、TCP参数设置接口
     *   *  Netty源码分析- AbstractBootstrap类源码
     *  3、添加和设置应用ChannelHandler接口
     *   *  Netty源码分析-ChannelInitializer类源码
         *  ChannelInitializer继承结构
     *  4、调用 Connect连接服务端

# Bootstrap引导类 #

Bootstrap是Socket客户端创建工具类，通过Bootstrap可以创建Netty的客户端，并发起异步TCP连接操作。Bootstrap不是线程安全。

EventLoopGroup group = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(group)
         .channel(NioSocketChannel.class)
         .option(ChannelOption.TCP_NODELAY, true)
         .handler(new ChannelInitializer<SocketChannel>() { 
             @Override
             public void initChannel(SocketChannel ch) throws Exception { 
                 ChannelPipeline p = ch.pipeline();
                 p.addLast(new LoggingHandler(LogLevel.INFO));
             }
         });
        ChannelFuture f = b.connect(HOST, PORT).sync();

## Bootstrap继承结构 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29reHVld2Vp_size_16_color_FFFFFF_t_70]

# Bootstrap常用功能 #

## 1、设置EventLoopGroup线程池 ##

## 2、TCP参数设置接口 ##

[ChannelOption参数][ChannelOption]

### Netty源码分析- AbstractBootstrap类源码 ###

private final Map<ChannelOption<?>, Object> options = new LinkedHashMap();
       
        /** * Channel实例被创建时，指定使用的ChannelOption参数。 * value参数为null，则移除这个ChannelOption参数 * * Allow to specify a {@link ChannelOption} which is used for the {@link Channel} * instances once they got created. * Use a value of {@code null} to remove a previous set {@link ChannelOption}. */
        public <T> B option(ChannelOption<T> option, T value) { 
            //判空
            if (option == null) { 
                throw new NullPointerException("option");
            } else { 
                if (value == null) { 
                    //从map中移除
                    synchronized(this.options) { 
                        this.options.remove(option);
                    }
                } else { 
                    //添加到map
                    synchronized(this.options) { 
                        this.options.put(option, value);
                    }
                }
    
                return this.self();
            }
        }

## 3、添加和设置应用ChannelHandler接口 ##

Bootstrap提供了ChannelInitializer简化ChannelHandler的编排，它继承了ChannelHandlerAdapter.

### Netty源码分析-ChannelInitializer类源码 ###

/** * Channel被注册时，这个方法会被调用。 * 方法返回后，这个实例将，从ChannelPipeline上移除 * * This method will be called once the {@link Channel} was registered. After the method returns this instance * will be removed from the {@link ChannelPipeline} of the {@link Channel}. **/
        protected abstract void initChannel(C var1) throws Exception;
    
        //TCP链路注册成功后，调用initChannel接口，用于设置用户ChannelHandler.
        private boolean initChannel(ChannelHandlerContext ctx) throws Exception { 
            // Guard against re-entrance.
            if (initMap.putIfAbsent(ctx, Boolean.TRUE) == null) {  
                try { 
                    //将应用自定义的ChannelHandler添加到ChannelPipeline中
                    initChannel((C) ctx.channel());
                } catch (Throwable cause) { 
                    // Explicitly call exceptionCaught(...) as we removed the handler before calling initChannel(...).
                    // We do so to prevent multiple calls to initChannel(...).
                    exceptionCaught(ctx, cause);
                } finally { 
                	//从ChannelPipeline中移除
                    remove(ctx);
                }
                return true;
            }
            return false;
        }

### ChannelInitializer继承结构 ###

![ChannelInitializer继承结构][ChannelInitializer]

## 4、调用 Connect连接服务端 ##

--------------------

–思想–  
专心协商大事时，别被琐事烦扰。  
不要被分歧束缚住–要么提交上级裁定，要么投票表决！

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29reHVld2Vp_size_16_color_FFFFFF_t_70]: /images/20230529/605d85c9b0e744df9558cfd069b28565.png
[ChannelOption]: https://blog.csdn.net/okxuewei/article/details/104862067
[ChannelInitializer]: /images/20230529/d2dc44173da149639e2b26f7115f0538.png