共计 21403 个字符，预计需要花费 54 分钟才能阅读完成。
从 ServiceConfig 类的 protocol 属性开始看起：
private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
public static <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {if (type == null)
throw new IllegalArgumentException("Extension type == null");
if (!type.isInterface()) {throw new IllegalArgumentException("Extension type(" + type + ") is not interface!");
}
if (!withExtensionAnnotation(type)) {
throw new IllegalArgumentException("Extension type(" + type +
") is not extension, because WITHOUT @" + SPI.class.getSimpleName() + "Annotation!");
}
ExtensionLoader<T> loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
// 初始化 loader
if (loader == null) {EXTENSION_LOADERS.putIfAbsent(type, new ExtensionLoader<T>(type));
loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
}
return loader;
}
loader 是通过 new ExtensionLoader<T>(type) 初始化的，进入 new ExtensionLoader<Protocol.class>(type) 构造方法：
private ExtensionLoader(Class<?> type) {
// 将 type 赋值给全局变量 type
this.type = type;
objectFactory = (type == ExtensionFactory.class ? null : ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptiveExtension());
}
因为此时 type 为 Protocol.class，不等于 ExtensionFactory.class，所以走的是 ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptiveExtension()。
第二次进入 getExtensionLoader 办法，此时 type 为 ExtensionFactory，初始化 loader，进入 new ExtensionLoader<ExtensionFactory.class>(type)，type 等于 ExtensionFactory.class，那么 objectFactory 赋值为 null，构造方法执行结束，返回 loader 为 ExtensionLoader<ExtensionFactory.class>，戒指执行 loader.getAdaptiveExtension())，即 ExtensionLoader<ExtensionFactory.class>.getAdaptiveExtension() 办法：
@SuppressWarnings("unchecked")
public T getAdaptiveExtension() {Object instance = cachedAdaptiveInstance.get();
if (instance == null) {if (createAdaptiveInstanceError == null) {synchronized (cachedAdaptiveInstance) {instance = cachedAdaptiveInstance.get();
if (instance == null) {
try {
// 进入这里
instance = createAdaptiveExtension();
cachedAdaptiveInstance.set(instance);
} catch (Throwable t) {
createAdaptiveInstanceError = t;
throw new IllegalStateException("fail to create adaptive instance:" + t.toString(), t);
}
}
}
} else {throw new IllegalStateException("fail to create adaptive instance:" + createAdaptiveInstanceError.toString(), createAdaptiveInstanceError);
}
}
return (T) instance;
}
@SuppressWarnings("unchecked")
private T createAdaptiveExtension() {
try {
// 先看 getAdaptiveExtensionClass
return injectExtension((T) getAdaptiveExtensionClass().newInstance());
} catch (Exception e) {throw new IllegalStateException("Can not create adaptive extension" + type + ", cause:" + e.getMessage(), e);
}
}
private Class<?> getAdaptiveExtensionClass() {
// 进入办法
getExtensionClasses();
if (cachedAdaptiveClass != null) {return cachedAdaptiveClass;}
return cachedAdaptiveClass = createAdaptiveExtensionClass();}
private Map<String, Class<?>> getExtensionClasses() {Map<String, Class<?>> classes = cachedClasses.get();
if (classes == null) {synchronized (cachedClasses) {classes = cachedClasses.get();
if (classes == null) {
// 进入 load 办法
classes = loadExtensionClasses();
cachedClasses.set(classes);
}
}
}
return classes;
}
// synchronized in getExtensionClasses
private Map<String, Class<?>> loadExtensionClasses() {
// 若 type 有 spi 注解且有 value，则将 cachedDefaultName 赋值为该 value
final SPI defaultAnnotation = type.getAnnotation(SPI.class);
if (defaultAnnotation != null) {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" + type.getName()
+ ":" + Arrays.toString(names));
}
if (names.length == 1) cachedDefaultName = names[0];
}
}
Map<String, Class<?>> extensionClasses = new HashMap<String, Class<?>>();
// 别离装载 META-INF/resources 目录下
// "META-INF/services/"，// "META-INF/dubbo/"，//"META-INF/dubbo/internal/" 三个目录的合乎 type 的类
loadDirectory(extensionClasses, DUBBO_INTERNAL_DIRECTORY);
loadDirectory(extensionClasses, DUBBO_DIRECTORY);
loadDirectory(extensionClasses, SERVICES_DIRECTORY);
return extensionClasses;
}
type 即为上文的 ExtensionFactory 类.
比方 META-INF/dubbo/internal/com.alibaba.dubbo.common.extension.ExtensionFactory 的内容如下：
adaptive=com.alibaba.dubbo.common.extension.factory.AdaptiveExtensionFactory
spi=com.alibaba.dubbo.common.extension.factory.SpiExtensionFactory
private void loadDirectory(Map<String, Class<?>> extensionClasses, String dir) {String fileName = dir + type.getName();
try {
Enumeration<java.net.URL> 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 resourceURL = urls.nextElement();
// 进入这里
loadResource(extensionClasses, classLoader, resourceURL);
}
}
} catch (Throwable t) {
logger.error("Exception when load extension class(interface:" +
type + ", description file:" + fileName + ").", t);
}
}
private void loadResource(Map<String, Class<?>> extensionClasses, ClassLoader classLoader, java.net.URL resourceURL) {
try {BufferedReader reader = new BufferedReader(new InputStreamReader(resourceURL.openStream(), "utf-8"));
try {
String line;
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) {
// 进入这里
loadClass(extensionClasses, resourceURL, Class.forName(line, true, classLoader), name);
}
} catch (Throwable t) {IllegalStateException e = new IllegalStateException("Failed to load extension class(interface:" + type + ", class line:" + line + ") in" + resourceURL + ", cause:" + t.getMessage(), t);
exceptions.put(line, e);
}
}
}
} finally {reader.close();
}
} catch (Throwable t) {
logger.error("Exception when load extension class(interface:" +
type + ", class file:" + resourceURL + ") in" + resourceURL, t);
}
}
private void loadClass(Map<String, Class<?>> extensionClasses, java.net.URL resourceURL, Class<?> clazz, String name) throws NoSuchMethodException {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.");
}
// 判断类上有没有 Adaptive 注解
if (clazz.isAnnotationPresent(Adaptive.class)) {
// 有的话则将 cachedAdaptiveClass 赋值为该类
// 比方 AdaptiveExtensionFactory
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());
}
}
// 判断是不是包装类
else if (isWrapperClass(clazz)) {
Set<Class<?>> wrappers = cachedWrapperClasses;
if (wrappers == null) {cachedWrapperClasses = new ConcurrentHashSet<Class<?>>();
wrappers = cachedWrapperClasses;
}
wrappers.add(clazz);
} else {clazz.getConstructor();
// 获取类简名，比方 SpringExtensionFactory 就是 spring，AdaptiveExtensionFactory 就是 adaptive
if (name == null || name.length() == 0) {name = findAnnotationName(clazz);
if (name.length() == 0) {throw new IllegalStateException("No such extension name for the class" + clazz.getName() + "in the config" + resourceURL);
}
}
String[] names = NAME_SEPARATOR.split(name);
if (names != null && names.length > 0) {
// 若类上有注解就放入 map，AdaptiveExtensionFactory 有注解，SpringExtensionFactory 没有
// 那么
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());
}
}
}
}
}
/** 判断办法就是有没有 type 为参数的构造方法 **/
private boolean isWrapperClass(Class<?> clazz) {
try {clazz.getConstructor(type);
return true;
} catch (NoSuchMethodException e) {return false;}
}
下面的代码简略说就是扫描 META-INF/services，META-INF/dubbo，META-INF/dubbo/internal 下的文件，找到合乎 type 实现类放到 map 里。
再回到 getAdaptiveExtensionClass 办法，cachedAdaptiveClass 对象在方才代码中被赋值为了
AdaptiveExtensionFactory，如果扫描过程中 cachedAdaptiveClass 没有被赋值，即没有实现类上有 @Adaptive 注解，那么就会执行 createAdaptiveExtensionClass 办法：
private Class<?> createAdaptiveExtensionClass() {String code = createAdaptiveExtensionClassCode();
ClassLoader classLoader = findClassLoader();
com.alibaba.dubbo.common.compiler.Compiler compiler = ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.common.compiler.Compiler.class).getAdaptiveExtension();
return compiler.compile(code, classLoader);
}
@SPI("javassist")
public interface Compiler {
/**
* Compile java source code.
*
* @param code Java source code
* @param classLoader classloader
* @return Compiled class
*/
Class<?> compile(String code, ClassLoader classLoader);
}
通过同样的代码，找到了 Compiler 的实现类 AdaptiveCompiler：
@Override
public Class<?> compile(String code, ClassLoader classLoader) {
Compiler compiler;
ExtensionLoader<Compiler> loader = ExtensionLoader.getExtensionLoader(Compiler.class);
String name = DEFAULT_COMPILER; // copy reference
//DEFAULT_COMPILER 为空
if (name != null && name.length() > 0) {compiler = loader.getExtension(name);
} else {
// 执行这里
compiler = loader.getDefaultExtension();}
return compiler.compile(code, classLoader);
}
/**
* Return default extension, return <code>null</code> if it's not configured.
*/
public T getDefaultExtension() {getExtensionClasses();
if (null == cachedDefaultName || cachedDefaultName.length() == 0
|| "true".equals(cachedDefaultName)) {return null;}
// 加载 cachedDefaultName 的类
return getExtension(cachedDefaultName);
}
下面的代码会将接口里 @SPI 注解指定的值赋给 cachedDefaultName，此时就会装载此类作为接口默认类。
通过 spi 获取 ExtensionLoader 实现，回到 createAdaptiveExtension 办法：
private T createAdaptiveExtension() {
try {
//getAdaptiveExtensionClass，通过 spi 实例化扩大类
//injectExtension 管制反转
return injectExtension((T) getAdaptiveExtensionClass().newInstance());
} catch (Exception e) {throw new IllegalStateException("Can not create adaptive extension" + type + ", cause:" + e.getMessage(), e);
}
}
private T injectExtension(T instance) {
try {
// objectFactory 在构造方法进行过赋值, 为 null，所以间接返回 instance
if (objectFactory != null) {for (Method method : instance.getClass().getMethods()) {if (method.getName().startsWith("set")
&& method.getParameterTypes().length == 1
&& Modifier.isPublic(method.getModifiers())) {
/**
* Check {@link DisableInject} to see if we need auto injection for this property
*/
// 过滤禁止主动注入的办法
if (method.getAnnotation(DisableInject.class) != null) {continue;}
Class<?> pt = method.getParameterTypes()[0];
try {String property = method.getName().length() > 3 ? method.getName().substring(3, 4).toLowerCase() + method.getName().substring(4) : "";
// 从 objectFactory 获取扩大类注入
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;
}
回到 getAdaptiveExtension 办法，instance 创立结束吗，赋值给 cachedAdaptiveInstance，
ExtensionLoader.getExtensionLoader(ExtensionFactory.class).getAdaptiveExtension() 办法执行结束，一句话概括就是通过 spi 拿到 ExtensionFactory 接口的实现类（AdaptiveExtensionFactory），并赋值给 objectFactory。
至此，new ExtensionLoader<Protocol.class>(Protocol.class) 办法执行结束，
再回到 getExtensionLoader<Protocol.class> 办法，将 new ExtensionLoader<Protocol.class>(Protocol.class) 对象赋值给 loader，即 ExtensionLoader.getExtensionLoader(Protocol.class) 办法获取到了该 loader，而后继续执行 loader.getAdaptiveExtension（）办法。
通过和下面一样的流程，始终到：
private Class<?> getAdaptiveExtensionClass() {
// 进入办法
getExtensionClasses();
//cachedAdaptiveClass 为空，因为 Protocol.class 没有实现类有 @Adaptive 注解
// 所以接着执行 createAdaptiveExtensionClass
if (cachedAdaptiveClass != null) {return cachedAdaptiveClass;}
return cachedAdaptiveClass = createAdaptiveExtensionClass();}
进入 createAdaptiveExtensionClass（）：
private Class<?> createAdaptiveExtensionClass() {
// 拼接代理类代码的字符串
String code = createAdaptiveExtensionClassCode();
ClassLoader classLoader = findClassLoader();
com.alibaba.dubbo.common.compiler.Compiler compiler = ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.common.compiler.Compiler.class).getAdaptiveExtension();
// 生产代理类
return compiler.compile(code, classLoader);
}
/**
* 生产代理类代码 string
* @return
*/
private String createAdaptiveExtensionClassCode() {StringBuilder codeBuilder = new StringBuilder();
Method[] methods = type.getMethods();
boolean hasAdaptiveAnnotation = false;
for (Method m : methods) {if (m.isAnnotationPresent(Adaptive.class)) {
hasAdaptiveAnnotation = true;
break;
}
}
// 实现类必须至多一个上有 @Adaptive 注解，否则不予代理
// no need to generate adaptive class since there's no adaptive method found.
if (!hasAdaptiveAnnotation)
throw new IllegalStateException("No adaptive method on extension" + type.getName() + ", refuse to create the adaptive class!");
// 拼包名、类名
codeBuilder.append("package").append(type.getPackage().getName()).append(";");
codeBuilder.append("\nimport").append(ExtensionLoader.class.getName()).append(";");
codeBuilder.append("\npublic class").append(type.getSimpleName()).append("$Adaptive").append("implements").append(type.getCanonicalName()).append("{");
// 遍历办法
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);
// 没有 @Adaptive 注解的办法抛异样
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;
// 办法参数必须要蕴含 URL.class
for (int i = 0; i < pts.length; ++i) {if (pts[i].equals(URL.class)) {
urlTypeIndex = i;
break;
}
}
// found parameter in URL type
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);
}
// did not find parameter in URL type
else {
String attribMethod = null;
// find URL getter method
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 adaptive 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();
// value is not set, use the value generated from class name as the 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;
// 判断参数是否蕴含 Invocation.class
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;
// 依据注解 value 拼接 url 调用代码
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 = (%<s)%s.getExtensionLoader(%s.class).getExtension(extName);",
type.getName(), ExtensionLoader.class.getSimpleName(), type.getName());
code.append(s);
// return statement
if (!rt.equals(void.class)) {code.append("\nreturn");
}
s = String.format("extension.%s(", method.getName());
code.append(s);
for (int i = 0; i < pts.length; i++) {if (i != 0)
code.append(",");
code.append("arg").append(i);
}
code.append(");");
}
codeBuilder.append("\npublic").append(rt.getCanonicalName()).append("").append(method.getName()).append("(");
for (int i = 0; i < pts.length; i++) {if (i > 0) {codeBuilder.append(",");
}
codeBuilder.append(pts[i].getCanonicalName());
codeBuilder.append(" ");
codeBuilder.append("arg").append(i);
}
codeBuilder.append(")");
if (ets.length > 0) {codeBuilder.append("throws");
for (int i = 0; i < ets.length; i++) {if (i > 0) {codeBuilder.append(",");
}
codeBuilder.append(ets[i].getCanonicalName());
}
}
codeBuilder.append("{");
codeBuilder.append(code.toString());
codeBuilder.append("\n}");
}
codeBuilder.append("\n}");
if (logger.isDebugEnabled()) {logger.debug(codeBuilder.toString());
}
return codeBuilder.toString();}
createAdaptiveExtensionClassCode（）办法就是拼接代理类代码的 string，供后续 javassist 生产代理类。拿到 complier 的实现类 AdaptiveCompiler 后，开始生产代理类，compiler.compile(code, classLoader)：
@Override
public Class<?> compile(String code, ClassLoader classLoader) {
Compiler compiler;
ExtensionLoader<Compiler> loader = ExtensionLoader.getExtensionLoader(Compiler.class);
String name = DEFAULT_COMPILER; // copy reference
//DEFAULT_COMPILER 为空
if (name != null && name.length() > 0) {compiler = loader.getExtension(name);
} else {
// 执行这里
compiler = loader.getDefaultExtension();}
return compiler.compile(code, classLoader);
}
/**
* Return default extension, return <code>null</code> if it's not configured.
*/
public T getDefaultExtension() {getExtensionClasses();
if (null == cachedDefaultName || cachedDefaultName.length() == 0
|| "true".equals(cachedDefaultName)) {return null;}
// 加载 cachedDefaultName 的类，即 compiler 接口上 spi 注解的 value，JavassistCompiler
return getExtension(cachedDefaultName);
}
拿到 JavassistCompiler 后，进行 compile：
@Override
public Class<?> compile(String code, ClassLoader classLoader) {code = code.trim();
Matcher matcher = PACKAGE_PATTERN.matcher(code);
String pkg;
if (matcher.find()) {pkg = matcher.group(1);
} else {pkg = "";}
matcher = CLASS_PATTERN.matcher(code);
String cls;
if (matcher.find()) {cls = matcher.group(1);
} else {throw new IllegalArgumentException("No such class name in" + code);
}
String className = pkg != null && pkg.length() > 0 ? pkg + "." + cls : cls;
try {
// 当类不存在时，办法会报错，就会执行 catch 里的 doCompile 办法，调用通过 javassist 进行生成类
return Class.forName(className, true, ClassHelper.getCallerClassLoader(getClass()));
} catch (ClassNotFoundException e) {if (!code.endsWith("}")) {throw new IllegalStateException("The java code not endsWith \"}\", code: \n" + code + "\n");
}
try {return doCompile(className, code);
} catch (RuntimeException t) {throw t;} catch (Throwable t) {throw new IllegalStateException("Failed to compile class, cause:" + t.getMessage() + ", class:" + className + ", code: \n" + code + "\n, stack:" + ClassUtils.toString(t));
}
}
}最初会通过 javassist 生成代理类 com.alibaba.dubbo.rpc.Protocol$Adaptive，残缺代码如下：
package com.alibaba.dubbo.rpc;
import com.alibaba.dubbo.common.extension.ExtensionLoader;
public class Protocol$Adaptive implements com.alibaba.dubbo.rpc.Protocol {public void destroy() {throw new UnsupportedOperationException("method public abstract void com.alibaba.dubbo.rpc.Protocol.destroy() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
}
public int getDefaultPort() {throw new UnsupportedOperationException("method public abstract int com.alibaba.dubbo.rpc.Protocol.getDefaultPort() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
}
public com.alibaba.dubbo.rpc.Invoker refer(java.lang.Class arg0, com.alibaba.dubbo.common.URL arg1) throws com.alibaba.dubbo.rpc.RpcException {if (arg1 == null) throw new IllegalArgumentException("url == null");
com.alibaba.dubbo.common.URL url = arg1;
String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url(" + url.toString() + ") use keys([protocol])");
com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.refer(arg0, arg1);
}
public com.alibaba.dubbo.rpc.Exporter export(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {if (arg0 == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
if (arg0.getUrl() == null) throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();
String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
if(extName == null) throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url(" + url.toString() + ") use keys([protocol])");
com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);
return extension.export(arg0);
}
} 对于 javassist 生成类的形式在此不再阐明，有趣味同学能够自行搜寻。
至此，Protocol 类通过 dubbo 的 spi 生成了扩大类 Protocol$Adaptive。
正文完
