一概述
最近由于公司业务减少，开始慢慢裁员了。程序猿们都已经清闲个把月了，不知道是不是过惯了忙碌的日子一下特别不舒服。被裁员可以拿到N+1的赔偿也是不错的哈！不知道下一个会不会是我，嘿嘿！上一节说到了如何自定义标签，今天说说dubbo的服务是如何发布出来的，研究了几天略有眉目。如果客观想看看，需要提前了解以下几个知识点：1.netty的使用，版本是3.x几的, 2. SPI技术的了解, 3.装饰模式（可能还涉及其它一些常见的模式就不提了），4java的反射机制，5.动态代理。
二服务发布
dubbo自定义标签 里面说过启动服务时会首先加载XML文件中的标签，解析出来的标签数据会装配到对应的实体类中，dubbo框架里面也是这样的。我们首先看看com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler类的实现
public class DubboNamespaceHandler extends NamespaceHandlerSupport {
static {
Version.checkDuplicate(DubboNamespaceHandler.class);
}
public void init() {
registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));
}
}这里面的逻辑主要就是解析dubbo的相关标签，并把属性值装配到对应的实体类中。研究服务发布我们重点看service标签的解析也就是15行的代码。因为ServiceBean实现了spring的ApplicationListener接口，所以也是一个监听器。在spring容器加载完成后触发contextrefreshedevent事件，这个事件会被实现了ApplicationListener接口的类监听到，执行对应的onApplicationEvent函数。我们看看ServiceBean类的代码
public void onApplicationEvent(ApplicationEvent event) {
if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
if (isDelay() && ! isExported() && ! isUnexported()) {
if (logger.isInfoEnabled()) {
logger.info("The service ready on spring started. service: " + getInterface());
}
export();
}
}
}这个监听方法最终调用了export方法来实现服务的发布处理。因为ServiceBean继承了ServiceConfig类，所以最终还是调用了ServiceConfig中的export方法：
public synchronized void export() {
if (provider != null) {
if (export == null) {
export = provider.getExport();//是否暴露
}
if (delay == null) {
delay = provider.getDelay();//是否延迟暴露
}
}
if (export != null && ! export.booleanValue()) {
return;
}
//是否延迟发布服务接口
if (delay != null && delay > 0) {
Thread thread = new Thread(new Runnable() {
public void run() {
try {
Thread.sleep(delay);//延迟睡眠后调用doExport发布接口
} catch (Throwable e) {
}
doExport();//直接发布接口
}
});
thread.setDaemon(true);//设置为守护线程
thread.setName("DelayExportServiceThread");
thread.start();
} else {
doExport();//直接发布接口
}
}里面做了很多逻辑判断，但最后还是调用了doExport方法，doExport做了很多配置上检查代码比较长也非重点就不贴出来，大家可以去查看相关源码。里面调用doExportUrls方法，代码如下：
private void doExportUrls() {
List<URL> registryURLs = loadRegistries(true);
for (ProtocolConfig protocolConfig : protocols) {
doExportUrlsFor1Protocol(protocolConfig, registryURLs);
}
}
这里我断点了下loadRegistries方法返回的就是注册地址，也就是服务在发布时需要到zookeeper中注册下。我这里配置两台zookeeper服务器，所以loadRegistries方法返回的是两个URL如下：registry://192.168.14.46:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&pid=524®istry=zookeeper×tamp=1498806201853
registry://192.168.14.47:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&pid=524®istry=zookeeper×tamp=1498806201986
private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
String name = protocolConfig.getName();
if (name == null || name.length() == 0) {
name = "dubbo";
}
String host = protocolConfig.getHost();
if (provider != null && (host == null || host.length() == 0)) {
host = provider.getHost();
}
boolean anyhost = false;
if (NetUtils.isInvalidLocalHost(host)) {
anyhost = true;
try {
host = InetAddress.getLocalHost().getHostAddress();
} catch (UnknownHostException e) {
logger.warn(e.getMessage(), e);
}
if (NetUtils.isInvalidLocalHost(host)) {
if (registryURLs != null && registryURLs.size() > 0) {
for (URL registryURL : registryURLs) {
try {
Socket socket = new Socket();
try {
SocketAddress addr = new InetSocketAddress(registryURL.getHost(), registryURL.getPort());
socket.connect(addr, 1000);
host = socket.getLocalAddress().getHostAddress();
break;
} finally {
try {
socket.close();
} catch (Throwable e) {}
}
} catch (Exception e) {
logger.warn(e.getMessage(), e);
}
}
}
if (NetUtils.isInvalidLocalHost(host)) {
host = NetUtils.getLocalHost();
}
}
}
Integer port = protocolConfig.getPort();
if (provider != null && (port == null || port == 0)) {
port = provider.getPort();
}
//获取协议默认的端口号
final int defaultPort = ExtensionLoader.getExtensionLoader(Protocol.class).getExtension(name).getDefaultPort();
if (port == null || port == 0) {
port = defaultPort;
}
if (port == null || port <= 0) {
port = getRandomPort(name);//随机生成端口
if (port == null || port < 0) {
port = NetUtils.getAvailablePort(defaultPort);
putRandomPort(name, port);
}
logger.warn("Use random available port(" + port + ") for protocol " + name);
}
Map<String, String> map = new HashMap<String, String>();
if (anyhost) {
map.put(Constants.ANYHOST_KEY, "true");
}
map.put(Constants.SIDE_KEY, Constants.PROVIDER_SIDE);
map.put(Constants.DUBBO_VERSION_KEY, Version.getVersion());
map.put(Constants.TIMESTAMP_KEY, String.valueOf(System.currentTimeMillis()));
if (ConfigUtils.getPid() > 0) {
map.put(Constants.PID_KEY, String.valueOf(ConfigUtils.getPid()));
}
appendParameters(map, application);
appendParameters(map, module);
appendParameters(map, provider, Constants.DEFAULT_KEY);
appendParameters(map, protocolConfig);
appendParameters(map, this);
if (methods != null && methods.size() > 0) {
for (MethodConfig method : methods) {
appendParameters(map, method, method.getName());
String retryKey = method.getName() + ".retry";
if (map.containsKey(retryKey)) {
String retryValue = map.remove(retryKey);
if ("false".equals(retryValue)) {
map.put(method.getName() + ".retries", "0");
}
}
List<ArgumentConfig> arguments = method.getArguments();
if (arguments != null && arguments.size() > 0) {
for (ArgumentConfig argument : arguments) {
//类型自动转换.
if(argument.getType() != null && argument.getType().length() >0){
Method[] methods = interfaceClass.getMethods();
//遍历所有方法
if(methods != null && methods.length > 0){
for (int i = 0; i < methods.length; i++) {
String methodName = methods[i].getName();
//匹配方法名称，获取方法签名.
if(methodName.equals(method.getName())){
Class<?>[] argtypes = methods[i].getParameterTypes();
//一个方法中单个callback
if (argument.getIndex() != -1 ){
if (argtypes[argument.getIndex()].getName().equals(argument.getType())){
appendParameters(map, argument, method.getName() + "." + argument.getIndex());
}else {
throw new IllegalArgumentException("argument config error : the index attribute and type attirbute not match :index :"+argument.getIndex() + ", type:" + argument.getType());
}
} else {
//一个方法中多个callback
for (int j = 0 ;j<argtypes.length ;j++) {
Class<?> argclazz = argtypes[j];
if (argclazz.getName().equals(argument.getType())){
appendParameters(map, argument, method.getName() + "." + j);
if (argument.getIndex() != -1 && argument.getIndex() != j){
throw new IllegalArgumentException("argument config error : the index attribute and type attirbute not match :index :"+argument.getIndex() + ", type:" + argument.getType());
}
}
}
}
}
}
}
}else if(argument.getIndex() != -1){
appendParameters(map, argument, method.getName() + "." + argument.getIndex());
}else {
throw new IllegalArgumentException("argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>");
}
}
}
} // end of methods for
}
if (ProtocolUtils.isGeneric(generic)) {
map.put("generic", generic);
map.put("methods", Constants.ANY_VALUE);
} else {
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put("revision", revision);
}
//根据服务实现的接口获取相关服务方法
String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
if(methods.length == 0) {
logger.warn("NO method found in service interface " + interfaceClass.getName());
map.put("methods", Constants.ANY_VALUE);
}
else {
map.put("methods", StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
}
}
if (! ConfigUtils.isEmpty(token)) {
if (ConfigUtils.isDefault(token)) {
map.put("token", UUID.randomUUID().toString());
} else {
map.put("token", token);
}
}
if ("injvm".equals(protocolConfig.getName())) {
protocolConfig.setRegister(false);
map.put("notify", "false");
}
// 导出服务
String contextPath = protocolConfig.getContextpath();
if ((contextPath == null || contextPath.length() == 0) && provider != null) {
contextPath = provider.getContextpath();
}
//根据Map中存储的属性组装URL地址
URL url = new URL(name, host, port, (contextPath == null || contextPath.length() == 0 ? "" : contextPath + "/") + path, map);
if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
.hasExtension(url.getProtocol())) {
url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
.getExtension(url.getProtocol()).getConfigurator(url).configure(url);
}
String scope = url.getParameter(Constants.SCOPE_KEY);
//配置为none不暴露
if (! Constants.SCOPE_NONE.toString().equalsIgnoreCase(scope)) {
//配置不是remote的情况下做本地暴露 (配置为remote，则表示只暴露远程服务)
if (!Constants.SCOPE_REMOTE.toString().equalsIgnoreCase(scope)) {
exportLocal(url);
}
//如果配置不是local则暴露为远程服务.(配置为local，则表示只暴露远程服务)
if (! Constants.SCOPE_LOCAL.toString().equalsIgnoreCase(scope) ){
if (logger.isInfoEnabled()) {
logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
}
if (registryURLs != null && registryURLs.size() > 0
&& url.getParameter("register", true)) {
for (URL registryURL : registryURLs) {
url = url.addParameterIfAbsent("dynamic", registryURL.getParameter("dynamic"));
URL monitorUrl = loadMonitor(registryURL);
if (monitorUrl != null) {
url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());
}
if (logger.isInfoEnabled()) {
logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
}
//通过proxyFactory对象生成接口实现类代理对象Invoker
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
//将Invoker对象封装到protocol协议对象中，同时开启socket服务监听端口，这里socket通信是使用netty框架来处理的
Exporter<?> exporter = protocol.export(invoker);
//添加对象到集合
exporters.add(exporter);
}
} else {
Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url);
Exporter<?> exporter = protocol.export(invoker);
exporters.add(exporter);
}
}
}
this.urls.add(url);
}
private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();//全局的协议对象
private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();//全局的代理工厂对象本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
