fix issue #3713: org.apache.dubbo.rpc.support.MockInvoker#getInterface should not return null (#3716)

Author: beiwei30

dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/support/wrapper/MockClusterInvoker.java

@@ -88,7 +88,7 @@ public Result invoke(Invocation invocation) throws RpcException {
                 if (e.isBiz()) {
                     throw e;
                 }
-                
+
                 if (logger.isWarnEnabled()) {
                     logger.warn("fail-mock: " + invocation.getMethodName() + " fail-mock enabled , url : " + directory.getUrl(), e);
                 }
@@ -105,7 +105,7 @@ private Result doMockInvoke(Invocation invocation, RpcException e) {
 
         List<Invoker<T>> mockInvokers = selectMockInvoker(invocation);
         if (CollectionUtils.isEmpty(mockInvokers)) {
-            minvoker = (Invoker<T>) new MockInvoker(directory.getUrl());
+            minvoker = (Invoker<T>) new MockInvoker(directory.getUrl(), directory.getInterface());
         } else {
             minvoker = mockInvokers.get(0);
         }

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/support/MockInvoker.java

@@ -46,9 +46,11 @@ final public class MockInvoker<T> implements Invoker<T> {
     private final static Map<String, Throwable> throwables = new ConcurrentHashMap<String, Throwable>();
 
     private final URL url;
+    private final Class<T> type;
 
-    public MockInvoker(URL url) {
+    public MockInvoker(URL url, Class<T> type) {
         this.url = url;
+        this.type = type;
     }
 
     public static Object parseMockValue(String mock) throws Exception {
@@ -251,7 +253,6 @@ public void destroy() {
 
     @Override
     public Class<T> getInterface() {
-        //FIXME
-        return null;
+        return type;
     }
 }

dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/support/MockProtocol.java

@@ -39,6 +39,6 @@ public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
 
     @Override
     public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
-        return new MockInvoker<T>(url);
+        return new MockInvoker<>(url, type);
     }
 }