filter

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/Filter.java

@@ -39,7 +39,7 @@ public interface Filter {
      * @param invoker    service
      * @param invocation invocation.
      * @return invoke result.
-     * @throws RpcException
+     * @throws RpcException 发生 RpcException 异常
      * @see com.alibaba.dubbo.rpc.Invoker#invoke(Invocation)
      */
     Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException;

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/RpcContext.java

@@ -56,23 +56,34 @@ import java.util.concurrent.TimeoutException;
  */
 public class RpcContext {
 
+    /**
+     * RpcContext 线程变量
+     */
     private static final ThreadLocal<RpcContext> LOCAL = new ThreadLocal<RpcContext>() {
+
         @Override
         protected RpcContext initialValue() {
             return new RpcContext();
         }
+
     };
 
+    /**
+     * 隐式参数集合
+     */
     private final Map<String, String> attachments = new HashMap<String, String>();
+    // 实际未使用
     private final Map<String, Object> values = new HashMap<String, Object>();
     /**
      * 异步调用 Future
      */
     private Future<?> future;
-
+    /**
+     * 可调用服务的 URL 对象集合
+     */
     private List<URL> urls;
     /**
-     * URL 对象
+     * 调用服务的 URL 对象
      */
     private URL url;
     /**
@@ -95,16 +106,27 @@ public class RpcContext {
      * 服务提供者地址
      */
     private InetSocketAddress remoteAddress;
-    @Deprecated
+
+    @Deprecated // DUBBO-325 废弃的，使用 urls 属性替代
     private List<Invoker<?>> invokers;
-    @Deprecated
+    @Deprecated // DUBBO-325 废弃的，使用 url 属性替代
     private Invoker<?> invoker;
-    @Deprecated
+    @Deprecated // DUBBO-325 废弃的，使用 methodName、parameterTypes、arguments 属性替代
     private Invocation invocation;
 
     // now we don't use the 'values' map to hold these objects
     // we want these objects to be as generic as possible
+    /**
+     * 请求
+     *
+     * 例如，在 RestProtocol
+     */
     private Object request;
+    /**
+     * 响应
+     *
+     * 例如，在 RestProtocol
+     */
     private Object response;
 
     protected RpcContext() {

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/RpcInvocation.java

@@ -50,8 +50,12 @@ public class RpcInvocation implements Invocation, Serializable {
      * 隐式参数集合
      */
     private Map<String, String> attachments;
-
-    private transient Invoker<?> invoker; // TODO 芋艿，transient
+    /**
+     * Invoker 对象
+     *
+     * 不序列化
+     */
+    private transient Invoker<?> invoker;
 
     public RpcInvocation() {
     }
@@ -120,6 +124,7 @@ public class RpcInvocation implements Invocation, Serializable {
         this.invoker = invoker;
     }
 
+    @Override
     public Invoker<?> getInvoker() {
         return invoker;
     }

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/filter/ClassLoaderFilter.java

@@ -27,16 +27,25 @@ import com.alibaba.dubbo.rpc.RpcException;
 /**
  * ClassLoaderInvokerFilter
  *
+ * 类加载器切换过滤器
+ *
+ * https://github.com/apache/incubator-dubbo/issues/1406
+ * https://github.com/apache/incubator-dubbo/issues/178
  */
 @Activate(group = Constants.PROVIDER, order = -30000)
 public class ClassLoaderFilter implements Filter {
 
+    @Override
     public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
+        // 获得原来的类加载器
         ClassLoader ocl = Thread.currentThread().getContextClassLoader();
+        // 切换当前线程的类加载器为服务接口的类加载器
         Thread.currentThread().setContextClassLoader(invoker.getInterface().getClassLoader());
+        // 服务调用
         try {
             return invoker.invoke(invocation);
         } finally {
+            // 切换当前线程的类加载器为原来的类加载器
             Thread.currentThread().setContextClassLoader(ocl);
         }
     }

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/filter/ConsumerContextFilter.java

@@ -30,23 +30,28 @@ import com.alibaba.dubbo.rpc.RpcInvocation;
 /**
  * ConsumerContextInvokerFilter
  *
+ * 服务消费者的 ContextFilter
  */
 @Activate(group = Constants.CONSUMER, order = -10000)
 public class ConsumerContextFilter implements Filter {
 
+    @Override
     public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
+        // 设置 RpcContext 对象
         RpcContext.getContext()
                 .setInvoker(invoker)
                 .setInvocation(invocation)
-                .setLocalAddress(NetUtils.getLocalHost(), 0)
-                .setRemoteAddress(invoker.getUrl().getHost(),
-                        invoker.getUrl().getPort());
+                .setLocalAddress(NetUtils.getLocalHost(), 0) // 本地地址
+                .setRemoteAddress(invoker.getUrl().getHost(), invoker.getUrl().getPort()); // 远程地址
+        // 设置 RpcInvocation 对象的 `invoker` 属性
         if (invocation instanceof RpcInvocation) {
             ((RpcInvocation) invocation).setInvoker(invoker);
         }
+        // 服务调用
         try {
             return invoker.invoke(invocation);
         } finally {
+            // 清理隐式参数集合
             RpcContext.getContext().clearAttachments();
         }
     }

dubbo-rpc/dubbo-rpc-api/src/main/java/com/alibaba/dubbo/rpc/filter/ContextFilter.java

@@ -32,11 +32,14 @@ import java.util.Map;
 /**
  * ContextInvokerFilter
  *
+ * 服务提供者的 ContextFilter
  */
 @Activate(group = Constants.PROVIDER, order = -10000)
 public class ContextFilter implements Filter {
 
+    @Override
     public Result invoke(Invoker<?> invoker, Invocation invocation) throws RpcException {
+        // 创建新的 `attachments` 集合，清理公用的隐式参数
         Map<String, String> attachments = invocation.getAttachments();
         if (attachments != null) {
             attachments = new HashMap<String, String>(attachments);
@@ -46,17 +49,18 @@ public class ContextFilter implements Filter {
             attachments.remove(Constants.DUBBO_VERSION_KEY);
             attachments.remove(Constants.TOKEN_KEY);
             attachments.remove(Constants.TIMEOUT_KEY);
-            attachments.remove(Constants.ASYNC_KEY);// Remove async property to avoid being passed to the following invoke chain.
+            attachments.remove(Constants.ASYNC_KEY); // Remove async property to avoid being passed to the following invoke chain.
+                                                     // 清空消费端的异步参数
         }
+        // 设置 RpcContext 对象
         RpcContext.getContext()
                 .setInvoker(invoker)
                 .setInvocation(invocation)
 //                .setAttachments(attachments)  // merged from dubbox
-                .setLocalAddress(invoker.getUrl().getHost(),
-                        invoker.getUrl().getPort());
-
+                .setLocalAddress(invoker.getUrl().getHost(), invoker.getUrl().getPort());
         // mreged from dubbox
         // we may already added some attachments into RpcContext before this filter (e.g. in rest protocol)
+        // 在此过滤器(例如rest协议)之前，我们可能已经在RpcContext中添加了一些附件。
         if (attachments != null) {
             if (RpcContext.getContext().getAttachments() != null) {
                 RpcContext.getContext().getAttachments().putAll(attachments);
@@ -64,14 +68,17 @@ public class ContextFilter implements Filter {
                 RpcContext.getContext().setAttachments(attachments);
             }
         }
-
+        // 设置 RpcInvocation 对象的 `invoker` 属性
         if (invocation instanceof RpcInvocation) {
             ((RpcInvocation) invocation).setInvoker(invoker);
         }
+        // 服务调用
         try {
             return invoker.invoke(invocation);
         } finally {
+            // 移除上下文
             RpcContext.removeContext();
         }
     }
+
 }
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