title: dubbo原始碼系列之filter的前生 tags:
- dubbo
- filter
- spi
- extensionLoader categories: dubbo date: 2017-06-25 18:18:53
dubbo的filter類似於spring的aop，提供了環繞增強功能。
快取是filter的一個很典型的實現。
那麼filter是如何被呼叫的呢？
收到spring荼毒多年很自然的想到了spring的aop實現===》換湯不換藥的動態代理
整篇故事要從invoker講起。
首先介紹一下Protocol介面
/*
* 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.rpc;
import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.common.extension.Adaptive;
import com.alibaba.dubbo.common.extension.SPI;
/**
* Protocol. (API/SPI, Singleton, ThreadSafe)
*
* @author william.liangf
*/
@SPI("dubbo")
public interface Protocol {
/**
* 獲取預設埠，當使用者沒有配置埠時使用。
*
* @return 預設埠
*/
int getDefaultPort();
/**
* 暴露遠端服務：<br>
* 1. 協議在接收請求時，應記錄請求來源方地址資訊：RpcContext.getContext().setRemoteAddress();<br>
* 2. export()必須是冪等的，也就是暴露同一個URL的Invoker兩次，和暴露一次沒有區別。<br>
* 3. export()傳入的Invoker由框架實現並傳入，協議不需要關心。<br>
*
* @param <T> 服務的型別
* @param invoker 服務的執行體
* @return exporter 暴露服務的引用，用於取消暴露
* @throws RpcException 當暴露服務出錯時丟擲，比如埠已佔用
*/
@Adaptive
<T> Exporter<T> export(Invoker<T> invoker) throws RpcException;
/**
* 引用遠端服務：<br>
* 1. 當使用者呼叫refer()所返回的Invoker物件的invoke()方法時，協議需相應執行同URL遠端export()傳入的Invoker物件的invoke()方法。<br>
* 2. refer()返回的Invoker由協議實現，協議通常需要在此Invoker中傳送遠端請求。<br>
* 3. 當url中有設定check=false時，連線失敗不能丟擲異常，並內部自動恢復。<br>
*
* @param <T> 服務的型別
* @param type 服務的型別
* @param url 遠端服務的URL地址
* @return invoker 服務的本地代理
* @throws RpcException 當連線服務提供方失敗時丟擲
*/
@Adaptive
<T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;
/**
* 釋放協議：<br>
* 1. 取消該協議所有已經暴露和引用的服務。<br>
* 2. 釋放協議所佔用的所有資源，比如連線和埠。<br>
* 3. 協議在釋放後，依然能暴露和引用新的服務。<br>
*/
void destroy();
}
複製程式碼SPI在上文已經描述過，可以得出結論 預設的protocol為dubbo
我們檢視檢視一下所有的protocol
registry=com.alibaba.dubbo.registry.integration.RegistryProtocol
filter=com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper
listener=com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper
mock=com.alibaba.dubbo.rpc.support.MockProtocol
injvm=com.alibaba.dubbo.rpc.protocol.injvm.InjvmProtocol
dubbo=com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol
rmi=com.alibaba.dubbo.rpc.protocol.rmi.RmiProtocol
hessian=com.alibaba.dubbo.rpc.protocol.hessian.HessianProtocol
com.alibaba.dubbo.rpc.protocol.http.HttpProtocol
com.alibaba.dubbo.rpc.protocol.webservice.WebServiceProtocol
thrift=com.alibaba.dubbo.rpc.protocol.thrift.ThriftProtocol
memcached=memcom.alibaba.dubbo.rpc.protocol.memcached.MemcachedProtocol
redis=com.alibaba.dubbo.rpc.protocol.redis.RedisProtocol
複製程式碼我們獲得了這些Protocol。 而Invoker的產生來自於
@Adaptive
<T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;
複製程式碼該方法有一個Adaptive標籤
package com.alibaba.dubbo.common.extension;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import com.alibaba.dubbo.common.URL;
/**
* 在{@link ExtensionLoader}生成Extension的Adaptive Instance時，為{@link ExtensionLoader}提供資訊。
*
* @author ding.lid
* @export
*
* @see ExtensionLoader
* @see URL
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
public @interface Adaptive {
/**
* 從{@link URL}的Key名，對應的Value作為要Adapt成的Extension名。
* <p>
* 如果{@link URL}這些Key都沒有Value，使用 用 預設的擴充套件（在介面的{@link SPI}中設定的值）。<br>
* 比如，<code>String[] {"key1", "key2"}</code>，表示
* <ol>
* <li>先在URL上找key1的Value作為要Adapt成的Extension名；
* <li>key1沒有Value，則使用key2的Value作為要Adapt成的Extension名。
* <li>key2沒有Value，使用預設的擴充套件。
* <li>如果沒有設定預設擴充套件，則方法呼叫會丟擲{@link IllegalStateException}。
* </ol>
* <p>
* 如果不設定則預設使用Extension介面類名的點分隔小寫字串。<br>
* 即對於Extension介面{@code com.alibaba.dubbo.xxx.YyyInvokerWrapper}的預設值為<code>String[] {"yyy.invoker.wrapper"}</code>
*
* @see SPI#value()
*/
String[] value() default {};
}
複製程式碼該註解可以同時出現在類或者方法上
這個註釋也很有意思，當使用該註解的時候會在Url引數上找到對應的param以此作為擴充套件，如果沒有則使用註解的value，否則就使用以點分割單詞的方式。
我們從原始碼分析一下
private void loadFile(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 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 {
clazz.getConstructor(type);
Set<Class<?>> wrappers = cachedWrapperClasses;
if (wrappers == null) {
cachedWrapperClasses = new ConcurrentHashSet<Class<?>>();
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);
}
}
複製程式碼這段程式碼負責從指定的資料夾下面載入指定Class的SPI（此處使用Dubbo自己實現而不是ServiceLoader）
為了便於說明 我們從Protocl來說明。
因此查詢檔案
META-INF/services/com.alibaba.dubbo.rpc.Protocol
META-INF/dubbo/com.alibaba.dubbo.rpc.Protocol
META-INF/dubbo/internal/com.alibaba.dubbo.rpc.Protocol
複製程式碼 registry=com.alibaba.dubbo.registry.integration.RegistryProtocol
filter=com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper
listener=com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper
mock=com.alibaba.dubbo.rpc.support.MockProtocol
injvm=com.alibaba.dubbo.rpc.protocol.injvm.InjvmProtocol
dubbo=com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol
rmi=com.alibaba.dubbo.rpc.protocol.rmi.RmiProtocol
hessian=com.alibaba.dubbo.rpc.protocol.hessian.HessianProtocol
com.alibaba.dubbo.rpc.protocol.http.HttpProtocol
com.alibaba.dubbo.rpc.protocol.webservice.WebServiceProtocol
thrift=com.alibaba.dubbo.rpc.protocol.thrift.ThriftProtocol
memcached=memcom.alibaba.dubbo.rpc.protocol.memcached.MemcachedProtocol
redis=com.alibaba.dubbo.rpc.protocol.redis.RedisProtocol
複製程式碼此處按照順序載入
- check該類是否在類上標有註解Adaptive 如果有那麼將該類標記為Adaptive類（校驗是都存在多個，如果存在多個則直接報錯）
- 如果不包含該註解那麼將該類初始化（check是否包含單個引數為com.alibaba.dubbo.rpc.Protocol的建構函式，如果有那麼將該類放入wrapper集合，否則使用午餐建構函式進行初始化）===》我們可以得出結論 如果spi檔案中對應的類為包含介面型別的單引數建構函式 那麼將被標記為wrapper，否則呼叫無引數建構函式進行初始化也就是真正的spi實現
- 那麼Adaptive的含義究竟是什麼呢？中文叫適配，通常來說我們會把這種理解為自適應。那麼自適應的結果是根據Url中的引數返回不同的實現（頗有依賴反轉的含義），當spi檔案中存在的型別不包含Adaptive的結果時我們會生成程式碼
private Class<?> getAdaptiveExtensionClass() {
getExtensionClasses();
if (cachedAdaptiveClass != null) {
return cachedAdaptiveClass;
}
return cachedAdaptiveClass = createAdaptiveExtensionClass();
}
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);
}
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;
}
}
// 完全沒有Adaptive方法，則不需要生成Adaptive類
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;
}
}
// 有型別為URL的引數
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);
}
// 引數沒有URL型別
else {
String attribMethod = null;
// 找到引數的URL屬性
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();
// 沒有設定Key，則使用“擴充套件點介面名的點分隔 作為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 = (%<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(");");
}
codeBuidler.append("\npublic " + rt.getCanonicalName() + " " + method.getName() + "(");
for (int i = 0; i < pts.length; i ++) {
if (i > 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();
}
這段程式碼負責生成Java程式碼，然後使用Compiler進行編譯，其次生成對應的class===》注意這段程式碼首先校驗對應的介面包含Adaptive的方法，如果不包含直接不生成（因為無需適配）
其次找到介面對應Adaptive方法的Url引數（也可能在JavaBean的引數中）根據URL獲取對應引數 依次來找到對應的適配（通過getExtension方法）
/**
* 返回指定名字的擴充套件。如果指定名字的擴充套件不存在，則拋異常 {@link IllegalStateException}.
*
* @param name
* @return
*/
@SuppressWarnings("unchecked")
public T getExtension(String name) {
if (name == null || name.length() == 0)
throw new IllegalArgumentException("Extension name == null");
if ("true".equals(name)) {
return getDefaultExtension();
}
Holder<Object> holder = cachedInstances.get(name);
if (holder == null) {
cachedInstances.putIfAbsent(name, new Holder<Object>());
holder = cachedInstances.get(name);
}
Object instance = holder.get();
if (instance == null) {
synchronized (holder) {
instance = holder.get();
if (instance == null) {
instance = createExtension(name);
holder.set(instance);
}
}
}
return (T) instance;
}
此處獲取指定名稱的Extension如果快取中沒有則去建立
@SuppressWarnings("unchecked")
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<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 {
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 {
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;
}
建立指定名稱的Extension（此處就是將spi檔案的對應檔案歸類後放在map中進行對映查詢）
此時會執行injectExtension這樣實現了依賴注入。
上文中還有個關鍵點，使用Wrapper來包裝對應的extension，比如Protocol此時就會有兩個包裝類
ProtocolFilterWrapper和ProtocolListenerWrapper
而filter的主要實現通過ProtocolFilterWrapper來完成。
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
return protocol.export(invoker);
}
return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));
}
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
return protocol.refer(type, url);
}
return buildInvokerChain(protocol.refer(type, url), Constants.REFERENCE_FILTER_KEY, Constants.CONSUMER);
}
public void destroy() {
protocol.destroy();
}
private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
Invoker<T> last = invoker;
List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
if (filters.size() > 0) {
for (int i = filters.size() - 1; i >= 0; i --) {
final Filter filter = filters.get(i);
final Invoker<T> next = last;
last = new Invoker<T>() {
public Class<T> getInterface() {
return invoker.getInterface();
}
public URL getUrl() {
return invoker.getUrl();
}
public boolean isAvailable() {
return invoker.isAvailable();
}
public Result invoke(Invocation invocation) throws RpcException {
return filter.invoke(next, invocation);
}
public void destroy() {
invoker.destroy();
}
@Override
public String toString() {
return invoker.toString();
}
};
}
}
return last;
}
複製程式碼filter的實現完全由buildInvokerChain來控制
下一篇再來細細分說filter的載入過程