你真的明白RPC 吗？一起来探究 RPC 的实质

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{ /** * service function * * @param name * @return */ String hello (String name) ; }

然后在 provider 模块实现接口，用自定注解 @SimpleProvider 标识，先看下注解内容

package com.glmapper.simple.provider.annotation;

/**
 * 自定义服务注解
 *
 * @author Jerry
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
// 标明可被 Spring 扫描
@Component 
public @interface SimpleProvider {

    Class<?> value();
}

注解使用了 @Component 标识，所以可被 spring 扫描到，接下来看实现类 HelloServiceImpl ：

package com.glmapper.simple.provider.service;

/**
 * service implement class
 *
 * @author: Jerry
 */
@SimpleProvider(HelloService.class)
public class HelloServiceImpl implements HelloService {

    /**
     * service function
     *
     * @param name
     * @return
     */
    @Override
    public String hello(String name) {
        return "Hello! " + name;
    }
}

在定义一个服务配置的类 SimpleProviderProperties ，方便通过 application.yml 文件配置，

package com.glmapper.simple.provider.property;

/**
 * provider properties
 *
 * @author: Jerry
 */
public class SimpleProviderProperties {

    /**
     * 暴露服务的端口
     */
    private Integer port;

    public Integer getPort() {
        return port;
    }

    public void setPort(Integer port) {
        this.port = port;
    }
}

到这里基础的类文件就已经结束了，下面开始服务初始化，入口 ProviderInitializer

package com.glmapper.simple.provider;

/**
 * 启动并注册服务
 *
 * @author Jerry
 */
public class ProviderInitializer implements ApplicationContextAware, InitializingBean {

    private static final Logger LOGGER = LoggerFactory.getLogger(ProviderInitializer.class);

    private SimpleProviderProperties providerProperties;

    /**
     * service registry
     */
    private ServiceRegistry serviceRegistry;

    /**
     * store interface and service implement mapping
     */
    private Map<String, Object> handlerMap = new HashMap<>();

    public ProviderInitializer(SimpleProviderProperties providerProperties, ServiceRegistry serviceRegistry) {
        this.providerProperties = providerProperties;
        this.serviceRegistry = serviceRegistry;
    }

    @Override
    public void setApplicationContext(ApplicationContext ctx) throws BeansException {
        // 获取被 SimpleProvider 注解的 Bean
        Map<String, Object> serviceBeanMap = ctx.getBeansWithAnnotation(SimpleProvider.class);
        if (MapUtils.isNotEmpty(serviceBeanMap)) {
            for (Object serviceBean : serviceBeanMap.values()) {
                String interfaceName = serviceBean.getClass().getAnnotation(SimpleProvider.class).value().getName();
                handlerMap.put(interfaceName, serviceBean);
            }
        }
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            ChannelHandler channelHandler = new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel channel) throws Exception {
                    channel.pipeline()
                            .addLast(new SimpleDecoder(SimpleRequest.class))
                            .addLast(new SimpleEncoder(SimpleResponse.class))
                            .addLast(new SimpleHandler(handlerMap));
                }
            };
            bootstrap.group(bossGroup, workerGroup)
                    .channel(NioServerSocketChannel.class)
                    .childHandler(channelHandler)
                    .option(ChannelOption.SO_BACKLOG, 128)
                    .childOption(ChannelOption.SO_KEEPALIVE, true);

            String host = getLocalHost();
            if (null == host) {
                LOGGER.error("can't get service address,because address is null");
                throw new SimpleException("can't get service address,because address is null");
            }
            int port = providerProperties.getPort();
            ChannelFuture future = bootstrap.bind(host, port).sync();
            LOGGER.debug("server started on port {}"

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