dubbo-源码阅读之容器启动

dubbo Main

例子

public class Start {
        public static void main(String[] args) throws Exception {

            com.alibaba.dubbo.container.Main.main(args);
        }
}

源码

public class Main {
    //系统变量
    public static final String CONTAINER_KEY = "dubbo.container";
    public static final String SHUTDOWN_HOOK_KEY = "dubbo.shutdown.hook";
    private static final Logger logger = LoggerFactory.getLogger(Main.class);
    //SPI的container Loader容器
    private static final ExtensionLoader<Container> loader = ExtensionLoader.getExtensionLoader(Container.class);
    private static final ReentrantLock LOCK = new ReentrantLock();
    private static final Condition STOP;

    public Main() {
    }

    public static void main(String[] args) {
        try {
            //如果没有启动参数
            if (args == null || args.length == 0) {
                //获得系统变量 如jvm参数配置的-Ddubbo.container=spiKey 如果没有则使用loader.getDefaultExtensionName()的
                String config = ConfigUtils.getProperty("dubbo.container", loader.getDefaultExtensionName());
                //分割
                args = Constants.COMMA_SPLIT_PATTERN.split(config);
            }
            //容器 可以多容器启动
            final List<Container> containers = new ArrayList();

            for(int i = 0; i < args.length; ++i) {
                //spi获取对应容器实现
                containers.add(loader.getExtension(args[i]));
            }

            logger.info("Use container type(" + Arrays.toString(args) + ") to run dubbo serivce.");
            /**
             * 埋点  jvm关闭时 关闭容器
             *kill pid会优雅关闭  则有新的请求拒绝 等没有进行中的请求 才关闭
             *kill -9并不会优雅关闭
             */
            if ("true".equals(System.getProperty("dubbo.shutdown.hook"))) {
                Runtime.getRuntime().addShutdownHook(new Thread() {
                    public void run() {
                        Iterator i$ = containers.iterator();

                        //遍历容器执行stop
                        while(i$.hasNext()) {
                            Container container = (Container)i$.next();

                            try {
                                container.stop();
                                Main.logger.info("Dubbo " + container.getClass().getSimpleName() + " stopped!");
                            } catch (Throwable var8) {
                                Main.logger.error(var8.getMessage(), var8);
                            }

                            try {
                                Main.LOCK.lock();
                                //类型Object的notify
                                Main.STOP.signal();
                            } finally {
                                Main.LOCK.unlock();
                            }
                        }

                    }
                });
            }

            Iterator i$ = containers.iterator();
            //循环启动容器
            while(i$.hasNext()) {
                Container container = (Container)i$.next();
                container.start();
                logger.info("Dubbo " + container.getClass().getSimpleName() + " started!");
            }

            System.out.println((new SimpleDateFormat("[yyyy-MM-dd HH:mm:ss]")).format(new Date()) + " Dubbo service server started!");
        } catch (RuntimeException var10) {
            var10.printStackTrace();
            logger.error(var10.getMessage(), var10);
            System.exit(1);
        }

        try {
            LOCK.lock();
            /**
             * 阻塞 防止应用程序结束
             * 类似object的wait()
             */
            STOP.await();
        } catch (InterruptedException var8) {
            logger.warn("Dubbo service server stopped, interrupted by other thread!", var8);
        } finally {
            LOCK.unlock();
        }

    }

    static {
        //condition可参考资料https://blog.csdn.net/andyzhaojianhui/article/details/79361454
        STOP = LOCK.newCondition();
    }
}

loader.getDefaultExtensionName()

public class ExtensionLoader<T> {

    private final Holder<Map<String, Class<?>>> cachedClasses = new Holder();
    public String getDefaultExtensionName() {
        this.getExtensionClasses();
        return this.cachedDefaultName;
    }
    private Map<String, Class<?>> getExtensionClasses() {
        //默认Holder容器是空的
        Map<String, Class<?>> classes = (Map)this.cachedClasses.get();
        if (classes == null) {
            Holder var2 = this.cachedClasses;
            synchronized(this.cachedClasses) {
                //防止缓存穿透 重复加载 加了一层判断
                classes = (Map)this.cachedClasses.get();
                if (classes == null) {
                    //真正加载的地方
                    classes = this.loadExtensionClasses();
                    this.cachedClasses.set(classes);
                }
            }
        }

        return classes;
    }

    private Map<String, Class<?>> loadExtensionClasses() {
        /**
         * 获得Container上的SPI注解 private static final ExtensionLoader<Container> loader = ExtensionLoader.getExtensionLoader(Container.class);
         * type为Container
         */
        SPI defaultAnnotation = (SPI)this.type.getAnnotation(SPI.class);
        if (defaultAnnotation != null) {
            //获取SPI上面的名字
            String value = defaultAnnotation.value();
            if ((value = value.trim()).length() > 0) {
                String[] names = NAME_SEPARATOR.split(value);
                if (names.length > 1) {
                    throw new IllegalStateException("more than 1 default extension name on extension " + this.type.getName() + ": " + Arrays.toString(names));
                }

                if (names.length == 1) {
                    this.cachedDefaultName = names[0];
                }
            }
        }

        Map<String, Class<?>> extensionClasses = new HashMap();
        //加载这个目录下的spi文件配置 META-INF/dubbo/internal/com.alibaba.dubbo.container.Container
        this.loadDirectory(extensionClasses, "META-INF/dubbo/internal/");
        //加载这个目录下的spi文件配置 META-INF/dubbo/com.alibaba.dubbo.container.Container
        this.loadDirectory(extensionClasses, "META-INF/dubbo/");
        //加载这个目录下的spi文件配置META-INF/dubbo/services/com.alibaba.dubbo.container.Container
        this.loadDirectory(extensionClasses, "META-INF/services/");
        return extensionClasses;
    }

    private void loadDirectory(Map<String, Class<?>> extensionClasses, String dir) {
        //加载这个目录下的spi文件配置 META-INF/dubbo/internal/com.alibaba.dubbo.container.Container
        String fileName = dir + this.type.getName();

        try {
            ClassLoader classLoader = findClassLoader();
            Enumeration urls;
            if (classLoader != null) {
                urls = classLoader.getResources(fileName);
            } else {
                urls = ClassLoader.getSystemResources(fileName);
            }

            if (urls != null) {
                while(urls.hasMoreElements()) {
                    java.net.URL resourceURL = (java.net.URL)urls.nextElement();
                    this.loadResource(extensionClasses, classLoader, resourceURL);
                }
            }
        } catch (Throwable var7) {
            logger.error("Exception when load extension class(interface: " + this.type + ", description file: " + fileName + ").", var7);
        }

    }

}

SpringContainer

例子

源码

public class SpringContainer implements Container {
    //可以系统变量指定spring xml配置
    public static final String SPRING_CONFIG = "dubbo.spring.config";
    //默认的位置
    public static final String DEFAULT_SPRING_CONFIG = "classpath*:META-INF/spring/*.xml";
    private static final Logger logger = LoggerFactory.getLogger(com.alibaba.dubbo.container.spring.SpringContainer.class);
    static ClassPathXmlApplicationContext context;

    public SpringContainer() {
    }

    public static ClassPathXmlApplicationContext getContext() {
        return context;
    }

    public void start() {
        //获取系统变量指定的spring配置文件位置
        String configPath = ConfigUtils.getProperty("dubbo.spring.config");
        if (configPath == null || configPath.length() == 0) {
            //没有指定取默认的
            configPath = "classpath*:META-INF/spring/*.xml";
        }
        //初始化spring容器
        context = new ClassPathXmlApplicationContext(configPath.split("[,\\s]+"));
        //start开始解析spring相关xml 以及dubbo基于spring2.0 schema解析dubbo相关配置以及初始化
        context.start();
    }

    public void stop() {
        try {
            if (context != null) {
                context.stop();
                context.close();
                context = null;
            }
        } catch (Throwable var2) {
            logger.error(var2.getMessage(), var2);
        }

    }
}