Dubbbo 记录源码疑问
dubbo 版本 2.5.3
1.JVM可以直接配置对应interface的url 或者指定dubbo路径文件，格式参照properties
ReferenceConfig.class line 185
String resolve = System.getProperty(interfaceName);
String resolveFile = null;
if (resolve == null || resolve.length() == 0) {
resolveFile = System.getProperty("dubbo.resolve.file");
if (resolveFile == null || resolveFile.length() == 0) {
File userResolveFile = new File(new File(System.getProperty("user.home")), "dubbo-resolve.properties");
if (userResolveFile.exists()) {
resolveFile = userResolveFile.getAbsolutePath();
}
}
if (resolveFile != null && resolveFile.length() > 0) {
Properties properties = new Properties();
FileInputStream fis = null;
try {
fis = new FileInputStream(new File(resolveFile));
properties.load(fis);
} catch (IOException e) {
throw new IllegalStateException("Unload " + resolveFile + ", cause: " + e.getMessage(), e);
} finally {
try {
if(null != fis) fis.close();
} catch (IOException e) {
logger.warn(e.getMessage(), e);
}
}
resolve = properties.getProperty(interfaceName);
}
}
if (resolve != null && resolve.length() > 0) {
url = resolve;
if (logger.isWarnEnabled()) {
if (resolveFile != null && resolveFile.length() > 0) {
logger.warn("Using default dubbo resolve file " + resolveFile + " replace " + interfaceName + "" + resolve + " to p2p invoke remote service.");
} else {
logger.warn("Using -D" + interfaceName + "=" + resolve + " to p2p invoke remote service.");
}
}
}2.这里是否走本地的相关判断没看懂
ReferenceConfig.class line 338
URL tmpUrl = new URL("temp", "localhost", 0, map);
final boolean isJvmRefer;
if (isInjvm() == null) {
if (url != null && url.length() > 0) { //指定URL的情况下，不做本地引用
isJvmRefer = false;
} else if (InjvmProtocol.getInjvmProtocol().isInjvmRefer(tmpUrl)) {
//默认情况下如果本地有服务暴露，则引用本地服务.
isJvmRefer = true;
} else {
isJvmRefer = false;
}
} else {
isJvmRefer = isInjvm().booleanValue();
}
if (isJvmRefer) {
URL url = new URL(Constants.LOCAL_PROTOCOL, NetUtils.LOCALHOST, 0, interfaceClass.getName()).addParameters(map);
invoker = refprotocol.refer(interfaceClass, url);
if (logger.isInfoEnabled()) {
logger.info("Using injvm service " + interfaceClass.getName());
}
} public boolean isInjvmRefer(URL url) {
final boolean isJvmRefer;
String scope = url.getParameter(Constants.SCOPE_KEY);
//本身已经是jvm协议了，走正常流程就是了.
if (Constants.LOCAL_PROTOCOL.toString().equals(url.getProtocol())) {
isJvmRefer = false;
} else if (Constants.SCOPE_LOCAL.equals(scope) || (url.getParameter("injvm", false))) {
//如果声明为本地引用
//scope=local || injvm=true 等价 injvm标签未来废弃掉.
isJvmRefer = true;
} else if (Constants.SCOPE_REMOTE.equals(scope)){
//声明了是远程引用，则不做本地引用
isJvmRefer = false;
} else if (url.getParameter(Constants.GENERIC_KEY, false)){
//泛化调用不走本地
isJvmRefer = false;
} else if (getExporter(exporterMap, url) != null) {
//默认情况下如果本地有服务暴露，则引用本地服务.
isJvmRefer = true;
} else {
isJvmRefer = false;
}
return isJvmRefer;
}3.异步dubbo调用如何实现值传递有一块看不懂
FutureFilter.class line 123
后来看了这篇文章就清楚了一些
https://blog.csdn.net/u013160932/article/details/81144471
private void fireReturnCallback(final Invoker invoker, final Invocation invocation, final Object result) {
final Method onReturnMethod = (Method)StaticContext.getSystemContext().get(StaticContext.getKey(invoker.getUrl(), invocation.getMethodName(), Constants.ON_RETURN_METHOD_KEY));
final Object onReturnInst = StaticContext.getSystemContext().get(StaticContext.getKey(invoker.getUrl(), invocation.getMethodName(), Constants.ON_RETURN_INSTANCE_KEY));
//not set onreturn callback
if (onReturnMethod == null && onReturnInst == null ){
return ;
}
if (onReturnMethod == null || onReturnInst == null ){
throw new IllegalStateException("service:" + invoker.getUrl().getServiceKey() +" has a onreturn callback config , but no such "+(onReturnMethod == null ? "method" : "instance")+" found. url:"+invoker.getUrl());
}
if (onReturnMethod != null && ! onReturnMethod.isAccessible()) {
onReturnMethod.setAccessible(true);
}
Object[] args = invocation.getArguments();
Object[] params ;
Class[] rParaTypes = onReturnMethod.getParameterTypes() ;
if (rParaTypes.length >1 ) {
if (rParaTypes.length == 2 && rParaTypes[1].isAssignableFrom(Object[].class)){
params = new Object[2];
params[0] = result;
params[1] = args ;
}else {
params = new Object[args.length + 1];
params[0] = result;
System.arraycopy(args, 0, params, 1, args.length);
}
} else {
params = new Object[] { result };
}
try {
onReturnMethod.invoke(onReturnInst, params);
} catch (InvocationTargetException e) {
fireThrowCallback(invoker, invocation, e.getTargetException());
} catch (Throwable e) {
fireThrowCallback(invoker, invocation, e);
}
}4. 一些因引用了外部包（包含自定义dubbo filter）可以使用url里面增加key的方式去掉对应的filter
类似: reference.filter=-xxx.XXXX
ProtocolFilterWrapper.class
public Invoker refer(Class type, URL url) throws RpcException {
return "registry".equals(url.getProtocol())?this.protocol.refer(type, url):buildInvokerChain(this.protocol.refer(type, url), "reference.filter", "consumer");
} ExtensionLoader.class
public List getActivateExtension(URL url, String key, String group) {
String value = url.getParameter(key);
return this.getActivateExtension(url, value != null && value.length() != 0?Constants.COMMA_SPLIT_PATTERN.split(value):null, group);
}
public List getActivateExtension(URL url, String[] values, String group) {
List exts = new ArrayList();
List names = values == null?new ArrayList(0):Arrays.asList(values);
String name;
if(!((List)names).contains("-default")) {
this.getExtensionClasses();
Iterator i$ = this.cachedActivates.entrySet().iterator();
while(i$.hasNext()) {
Entry entry = (Entry)i$.next();
name = (String)entry.getKey();
Activate activate = (Activate)entry.getValue();
if(this.isMatchGroup(group, activate.group())) {
T ext = this.getExtension(name);
if(!((List)names).contains(name) && !((List)names).contains("-" + name) && this.isActive(activate, url)) {
exts.add(ext);
}
}
}
Collections.sort(exts, ActivateComparator.COMPARATOR);
}
List usrs = new ArrayList();
for(int i = 0; i < ((List)names).size(); ++i) {
name = (String)((List)names).get(i);
if(!name.startsWith("-") && !((List)names).contains("-" + name)) {
if("default".equals(name)) {
if(usrs.size() > 0) {
exts.addAll(0, usrs);
usrs.clear();
}
} else {
T ext = this.getExtension(name);
usrs.add(ext);
}
}
}
if(usrs.size() > 0) {
exts.addAll(usrs);
}
return exts;
} 6.dubbo整个架构活用SPI方式，如果需要手动添加filter 直接自定义对应的映射文件即可
对应的类继承Filter类即可
ExtensionLoader.class
public class ExtensionLoader {
private static final Logger logger = LoggerFactory.getLogger(ExtensionLoader.class);
private static final String SERVICES_DIRECTORY = "META-INF/services/";
private static final String DUBBO_DIRECTORY = "META-INF/dubbo/";
private static final String DUBBO_INTERNAL_DIRECTORY = "META-INF/dubbo/internal/";//重点
private static final Pattern NAME_SEPARATOR = Pattern.compile("\\s*[,]+\\s*");
private static final ConcurrentMap, ExtensionLoader> EXTENSION_LOADERS = new ConcurrentHashMap();
private static final ConcurrentMap, Object> EXTENSION_INSTANCES = new ConcurrentHashMap();
private final Class type;
private final ExtensionFactory objectFactory;
private final ConcurrentMap, String> cachedNames = new ConcurrentHashMap();
private final Holder>> cachedClasses = new Holder();
private final Map cachedActivates = new ConcurrentHashMap();
private volatile Class cachedAdaptiveClass = null;
private final ConcurrentMap> cachedInstances = new ConcurrentHashMap();
private String cachedDefaultName;
private final Holder 7.通过SPI方式，如果实现类的构造参数有传入当前接口的构造方法，则默认调用该构造参数进行实例化
ExtensionLoader.class line 498
private T createExtension(String name) {
Class clazz = getExtensionClasses().get(name);
if (clazz == null) {
throw findException(name);
}
try {
T instance = (T) EXTENSION_INSTANCES.get(clazz);
if (instance == null) {
EXTENSION_INSTANCES.putIfAbsent(clazz, (T) clazz.newInstance());
instance = (T) EXTENSION_INSTANCES.get(clazz);
}
injectExtension(instance);
Set> wrapperClasses = cachedWrapperClasses;
if (wrapperClasses != null && wrapperClasses.size() > 0) {
for (Class wrapperClass : wrapperClasses) {
instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));
}
}
return instance;
} catch (Throwable t) {
throw new IllegalStateException("Extension instance(name: " + name + ", class: " +
type + ") could not be instantiated: " + t.getMessage(), t);
}
} ExtensionLoader.class line 597
private void loadFile(Map> extensionClasses, String dir) {
String fileName = dir + type.getName();
try {
Enumeration urls;
ClassLoader classLoader = findClassLoader();
if (classLoader != null) {
urls = classLoader.getResources(fileName);
} else {
urls = ClassLoader.getSystemResources(fileName);
}
if (urls != null) {
while (urls.hasMoreElements()) {
java.net.URL url = urls.nextElement();
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream(), "utf-8"));
try {
String line = null;
while ((line = reader.readLine()) != null) {
final int ci = line.indexOf('#');
if (ci >= 0) line = line.substring(0, ci);
line = line.trim();
if (line.length() > 0) {
try {
String name = null;
int i = line.indexOf('=');
if (i > 0) {
name = line.substring(0, i).trim();
line = line.substring(i + 1).trim();
}
if (line.length() > 0) {
Class clazz = Class.forName(line, true, classLoader);
if (! type.isAssignableFrom(clazz)) {
throw new IllegalStateException("Error when load extension class(interface: " +
type + ", class line: " + clazz.getName() + "), class "
+ clazz.getName() + "is not subtype of interface.");
}
if (clazz.isAnnotationPresent(Adaptive.class)) {
if(cachedAdaptiveClass == null) {
cachedAdaptiveClass = clazz;
} else if (! cachedAdaptiveClass.equals(clazz)) {
throw new IllegalStateException("More than 1 adaptive class found: "
+ cachedAdaptiveClass.getClass().getName()
+ ", " + clazz.getClass().getName());
}
} else {
try {
//这里是关键 如果有传入接口的构造参数则进入到wrapperClasses里面
clazz.getConstructor(type);
Set> wrappers = cachedWrapperClasses;
if (wrappers == null) {
cachedWrapperClasses = new ConcurrentHashSet>();
wrappers = cachedWrapperClasses;
}
wrappers.add(clazz);
} catch (NoSuchMethodException e) {
clazz.getConstructor();
if (name == null || name.length() == 0) {
name = findAnnotationName(clazz);
if (name == null || name.length() == 0) {
if (clazz.getSimpleName().length() > type.getSimpleName().length()
&& clazz.getSimpleName().endsWith(type.getSimpleName())) {
name = clazz.getSimpleName().substring(0, clazz.getSimpleName().length() - type.getSimpleName().length()).toLowerCase();
} else {
throw new IllegalStateException("No such extension name for the class " + clazz.getName() + " in the config " + url);
}
}
}
String[] names = NAME_SEPARATOR.split(name);
if (names != null && names.length > 0) {
Activate activate = clazz.getAnnotation(Activate.class);
if (activate != null) {
cachedActivates.put(names[0], activate);
}
for (String n : names) {
if (! cachedNames.containsKey(clazz)) {
cachedNames.put(clazz, n);
}
Class c = extensionClasses.get(n);
if (c == null) {
extensionClasses.put(n, clazz);
} else if (c != clazz) {
throw new IllegalStateException("Duplicate extension " + type.getName() + " name " + n + " on " + c.getName() + " and " + clazz.getName());
}
}
}
}
}
}
} catch (Throwable t) {
IllegalStateException e = new IllegalStateException("Failed to load extension class(interface: " + type + ", class line: " + line + ") in " + url + ", cause: " + t.getMessage(), t);
exceptions.put(line, e);
}
}
} // end of while read lines
} finally {
reader.close();
}
} catch (Throwable t) {
logger.error("Exception when load extension class(interface: " +
type + ", class file: " + url + ") in " + url, t);
}
} // end of while urls
}
} catch (Throwable t) {
logger.error("Exception when load extension class(interface: " +
type + ", description file: " + fileName + ").", t);
}
}
8.创建SPI接口的实现类的时候，dubbo实现了类似spring自动注入的行为
这里dubbo保证所有SPI的接口，只有一个实例，多个类型的接口子类通过入参进行调用子类方法
ExtensionLoader line 498
private T createExtension(String name) {
Class clazz = getExtensionClasses().get(name);
if (clazz == null) {
throw findException(name);
}
try {
T instance = (T) EXTENSION_INSTANCES.get(clazz);
if (instance == null) {
EXTENSION_INSTANCES.putIfAbsent(clazz, (T) clazz.newInstance());
instance = (T) EXTENSION_INSTANCES.get(clazz);
}
//进行自动注入
injectExtension(instance);
Set> wrapperClasses = cachedWrapperClasses;
if (wrapperClasses != null && wrapperClasses.size() > 0) {
for (Class wrapperClass : wrapperClasses) {
instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));
}
}
return instance;
} catch (Throwable t) {
throw new IllegalStateException("Extension instance(name: " + name + ", class: " +
type + ") could not be instantiated: " + t.getMessage(), t);
}
} ExtensionLoader line 523
private T injectExtension(T instance) {
try {
if (objectFactory != null) {
for (Method method : instance.getClass().getMethods()) {
if (method.getName().startsWith("set")
&& method.getParameterTypes().length == 1
&& Modifier.isPublic(method.getModifiers())) {
Class pt = method.getParameterTypes()[0];
try {
//根据setXXX的方法名截取bean的id进行注入
String property = method.getName().length() > 3 ? method.getName().substring(3, 4).toLowerCase() + method.getName().substring(4) : "";
Object object = objectFactory.getExtension(pt, property);
if (object != null) {
method.invoke(instance, object);
}
} catch (Exception e) {
logger.error("fail to inject via method " + method.getName()
+ " of interface " + type.getName() + ": " + e.getMessage(), e);
}
}
}
}
} catch (Exception e) {
logger.error(e.getMessage(), e);
}
return instance;
}9.ExtensionFactory如何初始化实例？
10.ExtensionLoader 懒加载SPI接口的代理类
private String createAdaptiveExtensionClassCode() {
StringBuilder codeBuidler = new StringBuilder();
Method[] methods = type.getMethods();
boolean hasAdaptiveAnnotation = false;
for(Method m : methods) {
if(m.isAnnotationPresent(Adaptive.class)) {
hasAdaptiveAnnotation = true;
break;
}
}
// 完全没有Adaptive方法，则不需要生成Adaptive类
if(! hasAdaptiveAnnotation)
throw new IllegalStateException("No adaptive method on extension " + type.getName() + ", refuse to create the adaptive class!");
codeBuidler.append("package " + type.getPackage().getName() + ";");
codeBuidler.append("\nimport " + ExtensionLoader.class.getName() + ";");
codeBuidler.append("\npublic class " + type.getSimpleName() + "$Adpative" + " implements " + type.getCanonicalName() + " {");
for (Method method : methods) {
Class rt = method.getReturnType();
Class[] pts = method.getParameterTypes();
Class[] ets = method.getExceptionTypes();
Adaptive adaptiveAnnotation = method.getAnnotation(Adaptive.class);
StringBuilder code = new StringBuilder(512);
if (adaptiveAnnotation == null) {
code.append("throw new UnsupportedOperationException(\"method ")
.append(method.toString()).append(" of interface ")
.append(type.getName()).append(" is not adaptive method!\");");
} else {
int urlTypeIndex = -1;
for (int i = 0; i < pts.length; ++i) {
if (pts[i].equals(URL.class)) {
urlTypeIndex = i;
break;
}
}
// 有类型为URL的参数
if (urlTypeIndex != -1) {
// Null Point check
String s = String.format("\nif (arg%d == null) throw new IllegalArgumentException(\"url == null\");",
urlTypeIndex);
code.append(s);
s = String.format("\n%s url = arg%d;", URL.class.getName(), urlTypeIndex);
code.append(s);
}
// 参数没有URL类型
else {
String attribMethod = null;
// 找到参数的URL属性
LBL_PTS:
for (int i = 0; i < pts.length; ++i) {
Method[] ms = pts[i].getMethods();
for (Method m : ms) {
String name = m.getName();
if ((name.startsWith("get") || name.length() > 3)
&& Modifier.isPublic(m.getModifiers())
&& !Modifier.isStatic(m.getModifiers())
&& m.getParameterTypes().length == 0
&& m.getReturnType() == URL.class) {
urlTypeIndex = i;
attribMethod = name;
break LBL_PTS;
}
}
}
if(attribMethod == null) {
throw new IllegalStateException("fail to create adative class for interface " + type.getName()
+ ": not found url parameter or url attribute in parameters of method " + method.getName());
}
// Null point check
String s = String.format("\nif (arg%d == null) throw new IllegalArgumentException(\"%s argument == null\");",
urlTypeIndex, pts[urlTypeIndex].getName());
code.append(s);
s = String.format("\nif (arg%d.%s() == null) throw new IllegalArgumentException(\"%s argument %s() == null\");",
urlTypeIndex, attribMethod, pts[urlTypeIndex].getName(), attribMethod);
code.append(s);
s = String.format("%s url = arg%d.%s();",URL.class.getName(), urlTypeIndex, attribMethod);
code.append(s);
}
String[] value = adaptiveAnnotation.value();
// 没有设置Key，则使用“扩展点接口名的点分隔 作为Key
if(value.length == 0) {
char[] charArray = type.getSimpleName().toCharArray();
StringBuilder sb = new StringBuilder(128);
for (int i = 0; i < charArray.length; i++) {
if(Character.isUpperCase(charArray[i])) {
if(i != 0) {
sb.append(".");
}
sb.append(Character.toLowerCase(charArray[i]));
}
else {
sb.append(charArray[i]);
}
}
value = new String[] {sb.toString()};
}
boolean hasInvocation = false;
for (int i = 0; i < pts.length; ++i) {
if (pts[i].getName().equals("com.alibaba.dubbo.rpc.Invocation")) {
// Null Point check
String s = String.format("\nif (arg%d == null) throw new IllegalArgumentException(\"invocation == null\");", i);
code.append(s);
s = String.format("\nString methodName = arg%d.getMethodName();", i);
code.append(s);
hasInvocation = true;
break;
}
}
String defaultExtName = cachedDefaultName;
String getNameCode = null;
for (int i = value.length - 1; i >= 0; --i) {
if(i == value.length - 1) {
if(null != defaultExtName) {
if(!"protocol".equals(value[i]))
if (hasInvocation)
getNameCode = String.format("url.getMethodParameter(methodName, \"%s\", \"%s\")", value[i], defaultExtName);
else
getNameCode = String.format("url.getParameter(\"%s\", \"%s\")", value[i], defaultExtName);
else
getNameCode = String.format("( url.getProtocol() == null ? \"%s\" : url.getProtocol() )", defaultExtName);
}
else {
if(!"protocol".equals(value[i]))
if (hasInvocation)
getNameCode = String.format("url.getMethodParameter(methodName, \"%s\", \"%s\")", value[i], defaultExtName);
else
getNameCode = String.format("url.getParameter(\"%s\")", value[i]);
else
getNameCode = "url.getProtocol()";
}
}
else {
if(!"protocol".equals(value[i]))
if (hasInvocation)
getNameCode = String.format("url.getMethodParameter(methodName, \"%s\", \"%s\")", value[i], defaultExtName);
else
getNameCode = String.format("url.getParameter(\"%s\", %s)", value[i], getNameCode);
else
getNameCode = String.format("url.getProtocol() == null ? (%s) : url.getProtocol()", getNameCode);
}
}
code.append("\nString extName = ").append(getNameCode).append(";");
// check extName == null?
String s = String.format("\nif(extName == null) " +
"throw new IllegalStateException(\"Fail to get extension(%s) name from url(\" + url.toString() + \") use keys(%s)\");",
type.getName(), Arrays.toString(value));
code.append(s);
s = String.format("\n%s extension = (% 0) {
codeBuidler.append(", ");
}
codeBuidler.append(pts[i].getCanonicalName());
codeBuidler.append(" ");
codeBuidler.append("arg" + i);
}
codeBuidler.append(")");
if (ets.length > 0) {
codeBuidler.append(" throws ");
for (int i = 0; i < ets.length; i ++) {
if (i > 0) {
codeBuidler.append(", ");
}
codeBuidler.append(pts[i].getCanonicalName());
}
}
codeBuidler.append(" {");
codeBuidler.append(code.toString());
codeBuidler.append("\n}");
}
codeBuidler.append("\n}");
if (logger.isDebugEnabled()) {
logger.debug(codeBuidler.toString());
}
return codeBuidler.toString();
} Dubbo的大致接口看了一下，发现所有接口的起始位置都在ExtensionLoader类里面。
所有的适配行为，都是根据Url的parameters来进行适配，而这个机制就是来自上面的代码
1.默认取SPI接口方法参数内的Url类型的对象
2.否则通过接口方法参数对象数组内某个对象包含get方法的返回值为Url的方法取到Url对象
3.接口名字为Protocol或者@Adaptive的key包含protocol的方法，通过Url的getProtocol获取extName(扩展类名 即SPI文件的key)
1）如果不为Protocol或者@Adaptive的key包含protocol的话 且 接口参数不包含Invocation，则通过Url的getParamter进行获取extName
2）否则通过Url的getMethodParameter获取extName
ps：getMethodParameter和getParameter的区别就是key是methodName+"."+key和直接用key查询的区别，如果methodName+"."+key没有在parameters里面的话最后还是会通getParameter进行获取
4.生成的源文件最终还是通过ExtensionLoader获取执行子类对象调用方法
所以整个Dubbo框架驱动都是通过Url对象，通过?cluster={customizedClusterKey}来适配SPI子类
11.Invoker的调用路径 Invoker.invoke->Directory.list -> Router.route -> LoanBalance.select
Invoke的调用模式有点装饰者模式的感觉 Invoke(StaticDirectory(Invoker(RegistryDirectory)))
RegistryDirectory的缓存的methodInvokerMap和urlInvokerMap 根据zookeeper的watch监听状态动态更新，保证每次调用都调用新的地址
12.MonitorFilter在调用完会收集相关信息
MonitorFilter line 59
public Result invoke(Invoker invoker, Invocation invocation) throws RpcException {
if (invoker.getUrl().hasParameter(Constants.MONITOR_KEY)) {
RpcContext context = RpcContext.getContext(); // 提供方必须在invoke()之前获取context信息
long start = System.currentTimeMillis(); // 记录起始时间戮
getConcurrent(invoker, invocation).incrementAndGet(); // 并发计数
try {
Result result = invoker.invoke(invocation); // 让调用链往下执行
collect(invoker, invocation, result, context, start, false);
return result;
} catch (RpcException e) {
collect(invoker, invocation, null, context, start, true);
throw e;
} finally {
getConcurrent(invoker, invocation).decrementAndGet(); // 并发计数
}
} else {
return invoker.invoke(invocation);
}
}
13.ExtensionLoader的cachedDefaultName默认取接口的SPI里面的value值作为默认的扩展子类名字
所以在RegistryProtocol.refer方法中调用Cluster.join(Directory)即使Directory内的URL没有包含cluster的配置 也会直接
调用FailoverCluster的方法
@SPI(FailoverCluster.NAME)
public interface Cluster {
/**
* Merge the directory invokers to a virtual invoker.
*
* @param
* @param directory
* @return cluster invoker
* @throws RpcException
*/
@Adaptive
Invoker join(Directory directory) throws RpcException;
} 14.ExtensionFactory @Adaptive
在看ExtensionFactory的子类AdaptiveExtensionFactory的时候，发现了他的Class上有打了@Adaptive，然而其他两个子类并没有SpiExtensionFactory，SpringExtensionFactory，又重新看了一下ExtensionLoader初始化载入资源的方法
发现如果有标识@Adaptive的class会默认是这个SPI接口的实现类，而不会生成字节码通过入参去驱动具体子类，具体实现如下
ExtensionLoader line 633
if (clazz.isAnnotationPresent(Adaptive.class)) {
if(cachedAdaptiveClass == null) {
cachedAdaptiveClass = clazz;
} else if (! cachedAdaptiveClass.equals(clazz)) {
throw new IllegalStateException("More than 1 adaptive class found: "
+ cachedAdaptiveClass.getClass().getName()
+ ", " + clazz.getClass().getName());
}
} ExtensionLoader line 727
private Class getAdaptiveExtensionClass() {
getExtensionClasses();
if (cachedAdaptiveClass != null) {
return cachedAdaptiveClass;
}
return cachedAdaptiveClass = createAdaptiveExtensionClass();
}
15.因为@Service没有元注解@Inherited，如果通过annotation方式启动dubbo的话，打了注解类有涉及切面的话都会启动不起来
16.@Adaptive 具有这个标识的class作为默认的实现子类
17.加了@Activate的注解，可以通过url里面配置{interface}=-xxx来禁止filter的某各类，或者xxx=(非false 0 null N/A)来开启某个类
比如 ProtocolFilterWrapper， 见getActivateExtension
@Activate 有了value配置，则url中必须设置xxx=非(false 0 null N/A) 来开启，没有value则默认开启 见 ExtensionLoader.getActivateExtension 暂时dubbo应用里面只有Filter、TelnetHandler和InvokerListener会用到
18.一些默认配置，优先读取jvm启动参数，如果没有则优先寻找dubbo.properties.file在jvm启动参数是否配置了路径，否则在环境变量里寻找dubbo.properties.file是否配置了value，否则默认取服务的dubbo.properties文件
19.消费端设置的配置优先级高于服务端
/**
* 合并url参数 顺序为override > -D >Consumer > Provider
* @param providerUrl
* @param overrides
* @return
*/
private URL mergeUrl(URL providerUrl){
}