/*
* Copyright 1999-2011 Alibaba Group.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.alibaba.dubbo.common;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.regex.Pattern;
import com.alibaba.dubbo.common.bytecode.ClassGenerator;
import com.alibaba.dubbo.common.logger.Logger;
import com.alibaba.dubbo.common.logger.LoggerFactory;
import com.alibaba.dubbo.common.utils.ConcurrentHashSet;
import com.alibaba.dubbo.common.utils.Reference;
import com.alibaba.dubbo.common.utils.StringUtils;
/**
* Dubbo使用的扩展点获取。<p>
* <ul>
* <li>自动注入关联扩展点。</li>
* <li>自动Wrap上扩展点的Wrap类。</li>
* <li>缺省获得的的扩展点是一个Adaptive Instance。
* </ul>
*
* @see <a href="http://java.sun.com/j2se/1.5.0/docs/guide/jar/jar.html#Service%20Provider">JDK5.0的自动发现机制实现</a>
*
* @author william.liangf
* @author ding.lid
*
* @see Extension
* @see Adaptive
*/
public class ExtensionLoader<T> {
private static final Logger logger = LoggerFactory.getLogger(ExtensionLoader.class);
private static final String SERVICES_DIRECTORY = "META-INF/services/";
private static final Pattern NAME_SEPARATOR = Pattern.compile("\\s*[,]+\\s*");
private static final ConcurrentMap<Class<?>, ExtensionLoader<?>> EXTENSION_LOADERS = new ConcurrentHashMap<Class<?>, ExtensionLoader<?>>();
private final Class<?> type;
private final Reference<Map<String, Class<?>>> cachedClasses = new Reference<Map<String,Class<?>>>();
private final ConcurrentMap<String, Reference<Object>> cachedInstances = new ConcurrentHashMap<String, Reference<Object>>();
private volatile Class<?> cachedAdaptiveClass = null;
private final Reference<Object> cachedAdaptiveInstance = new Reference<Object>();
private volatile Throwable createAdaptiveInstanceError;
private Set<Class<?>> cachedWrapperClasses;
private String cachedDefaultName;
private Map<String, IllegalStateException> exceptions = new ConcurrentHashMap<String, IllegalStateException>();
@SuppressWarnings("unchecked")
public static <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {
if (type == null)
throw new IllegalArgumentException("Extension type == null");
ExtensionLoader<T> loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
if (loader == null) {
EXTENSION_LOADERS.putIfAbsent(type, new ExtensionLoader<T>(type));
loader = (ExtensionLoader<T>) EXTENSION_LOADERS.get(type);
}
return loader;
}
private ExtensionLoader(Class<?> type) {
this.type = type;
}
@SuppressWarnings("unchecked")
public T getExtension(String name) {
if (name == null || name.length() == 0)
throw new IllegalArgumentException("Extension name == null");
Reference<Object> reference = cachedInstances.get(name);
if (reference == null) {
cachedInstances.putIfAbsent(name, new Reference<Object>());
reference = cachedInstances.get(name);
}
Object instance = reference.get();
if (instance == null) {
synchronized (reference) {
instance = reference.get();
if (instance == null) {
instance = createExtension(name);
reference.set(instance);
}
}
}
return (T) instance;
}
/**
* 返回缺省的扩展，如果没有设置则返回<code>null</code>。
*/
public T getDefaultExtension() {
getExtensionClasses();
if(null == cachedDefaultName || cachedDefaultName.length() == 0) {
return null;
}
return getExtension(cachedDefaultName);
}
public boolean hasExtension(String name) {
if (name == null || name.length() == 0)
throw new IllegalArgumentException("Extension name == null");
try {
return getExtensionClass(name) != null;
} catch (Throwable t) {
return false;
}
}
public Set<String> getSupportedExtensions() {
Map<String, Class<?>> clazzes = getExtensionClasses();
return Collections.unmodifiableSet(new TreeSet<String>(clazzes.keySet()));
}
public Set<String> getLoadedExtensions() {
return Collections.unmodifiableSet(new TreeSet<String>(cachedInstances.keySet()));
}
/**
* 返回缺省的扩展点名，如果没有设置缺省则返回<code>null</code>。
*/
public String getDefaultExtensionName() {
getExtensionClasses();
return cachedDefaultName;
}
@SuppressWarnings("unchecked")
public T getAdaptiveExtension() {
Object instance = cachedAdaptiveInstance.get();
if (instance == null) {
if(createAdaptiveInstanceError == null) {
synchronized (cachedAdaptiveInstance) {
instance = cachedAdaptiveInstance.get();
if (instance == null) {
try {
instance = createAdaptiveExtension();
cachedAdaptiveInstance.set(instance);
} catch (Throwable t) {
createAdaptiveInstanceError = t;
rethrowAsRuntime(t, "fail to create adaptive instance: ");
}
}
}
}
else {
rethrowAsRuntime(createAdaptiveInstanceError, "fail to create adaptive instance: ");
}
}
return (T) instance;
}
private static void rethrowAsRuntime(Throwable t, String message) {
if(t instanceof RuntimeException)
throw (RuntimeException)t;
else
throw new IllegalStateException(message + t.toString(), t);
}
private IllegalStateException findException(String name) {
for (Map.Entry<String, IllegalStateException> entry : exceptions.entrySet()) {
if (entry.getKey().toLowerCase().contains(name.toLowerCase())) {
return entry.getValue();
}
}
StringBuilder buf = new StringBuilder("No such extension " + type.getName() + " by name " + name + ", possible causes: ");
int i = 1;
for (Map.Entry<String, IllegalStateException> entry : exceptions.entrySet()) {
buf.append("\r\n(");
buf.append(i ++);
buf.append(") ");
buf.append(entry.getKey());
buf.append(":\r\n");
buf.append(StringUtils.toString(entry.getValue()));
}
return new IllegalStateException(buf.toString());
}
@SuppressWarnings("unchecked")
private T createExtension(String name) {
Class<?> clazz = getExtensionClasses().get(name);
if (clazz == null) {
throw findException(name);
}
try {
T instance = injectExtension((T) clazz.newInstance());
Set<Class<?>> 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);
}
}
private T injectExtension(T instance) {
try {
for (Method method : instance.getClass().getMethods()) {
if (method.getName().startsWith("set")
&& method.getParameterTypes().length == 1
&& Modifier.isPublic(method.getModifiers())) {
Class<?> pt = method.getParameterTypes()[0];
if (pt.isInterface() && getExtensionLoader(pt).getSupportedExtensions().size() > 0) {
try {
Object adaptive = getExtensionLoader(pt).getAdaptiveExtension();
method.invoke(instance, adaptive);
} 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;
}
private Class<?> getExtensionClass(String name) {
if (type == null)
throw new IllegalArgumentException("Extension type == null");
if (name == null)
throw new IllegalArgumentException("Extension name == null");
Class<?> clazz = getExtensionClasses().get(name);
if (clazz == null)
throw new IllegalStateException("No such extension \"" + name + "\" for " + type.getName() + "!");
return clazz;
}
private Map<String, Class<?>> getExtensionClasses() {
Map<String, Class<?>> classes = cachedClasses.get();
if (classes == null) {
synchronized (cachedClasses) {
classes = cachedClasses.get();
if (classes == null) {
classes = loadExtensionClasses();
cachedClasses.set(classes);
}
}
}
return classes;
}
private Map<String, Class<?>> loadExtensionClasses() {
final Extension defaultAnnotation = type.getAnnotation(Extension.class);
if(defaultAnnotation != null) {
String[] names = NAME_SEPARATOR.split(defaultAnnotation.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];
}
ClassLoader classLoader = findClassLoader();
Map<String, Class<?>> extensionClasses = new HashMap<String, Class<?>>();
String fileName = null;
try {
fileName = SERVICES_DIRECTORY + type.getName();
Enumeration<java.net.URL> urls;
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 {
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 {
clazz.getConstructor(type);
Set<Class<?>> wrappers = cachedWrapperClasses;
if (wrappers == null) {
cachedWrapperClasses = new ConcurrentHashSet<Class<?>>();
wrappers = cachedWrapperClasses;
}
wrappers.add(clazz);
} catch (NoSuchMethodException e) {
clazz.getConstructor();
Extension extension = clazz.getAnnotation(Extension.class);
if (extension == null) {
throw new IllegalStateException("No such @Extension annotation in class " + clazz.getName());
}
String name = extension.value();
if (name == null || name.length() == 0) {
throw new IllegalStateException("Illegal @Extension annotation in class " + clazz.getName());
}
String[] names = NAME_SEPARATOR.split(name);
for (String n : names) {
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);
}
return extensionClasses;
}
@SuppressWarnings("unchecked")
private T createAdaptiveExtension() {
try {
return injectExtension((T) getAdaptiveExtensionClass().newInstance());
} catch (Exception e) {
throw new IllegalStateException("Can not create adaptive extenstion " + type + ", cause: " + e.getMessage(), e);
}
}
private Class<?> getAdaptiveExtensionClass() {
getExtensionClasses();
if (cachedAdaptiveClass != null) {
return cachedAdaptiveClass;
}
return cachedAdaptiveClass = createAdaptiveExtensionClass();
}
private Class<?> createAdaptiveExtensionClass() {
ClassLoader classLoader = findClassLoader();
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!");
ClassGenerator cg = ClassGenerator.newInstance(classLoader);
cg.setClassName(type.getName() + "$Adpative");
cg.addInterface(type);
cg.addDefaultConstructor();
for (Method method : methods) {
Class<?> rt = method.getReturnType();
Class<?>[] pts = method.getParameterTypes();
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("if (arg%d == null) { throw new IllegalArgumentException(\"url == null\"); }",
urlTypeIndex);
code.append(s);
s = String.format("%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("if (arg%d == null) { throw new IllegalArgumentException(\"%s argument == null\"); }",
urlTypeIndex, pts[urlTypeIndex].getName());
code.append(s);
s = String.format("if (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()};
}
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]))
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]))
getNameCode = String.format("url.getParameter(\"%s\")", value[i]);
else
getNameCode = "url.getProtocol()";
}
}
else {
if(!"protocol".equals(value[i]))
getNameCode = String.format("url.getParameter(\"%s\", %s)", value[i], getNameCode);
else
getNameCode = String.format("( url.getProtocol() == null ? (%s) : url.getProtocol() )", getNameCode);
}
}
code.append("String extName = ").append(getNameCode).append(";");
// check extName == null?
String s = String.format("if(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("%s extension = (%<s)%s.getExtensionLoader(%s.class).getExtension(extName);",
type.getName(), ExtensionLoader.class.getName(), type.getName());
code.append(s);
// return statement
if (!rt.equals(void.class)) {
code.append("return ");
}
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(");");
}
cg.addMethod(method.getName(), method.getModifiers(), rt, pts,
method.getExceptionTypes(), code.toString());
}
return cg.toClass();
}
private static ClassLoader findClassLoader() {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader != null) {
return classLoader;
}
classLoader = ExtensionLoader.class.getClassLoader();
return classLoader;
}
@Override
public String toString() {
return this.getClass().getName() + "[" + type.getName() + "]";
}
}