Fix "echo" method with one param bug.

Issue: #37
Signed-off-by: Hechao Li <hechaol@outlook.com>

json-rpc/src/main/java/com/vmware/ovsdb/jsonrpc/v1/service/impl/JsonRpcV1ServerImpl.java

@@ -139,25 +139,19 @@ private Object[] toMethodParams(ArrayNode paramsNode, Method method) {
     int actualParamSize = paramsNode.size();
 
     Object[] actualParams = new Object[methodParamSize];
-    if (methodParamSize != actualParamSize) {
-      // This is not an error only if the last arg is a vararg
-      // And the actual params number must be >= methods params number - 1
-      // For e.g. if a methods has n params, the last one is an vararg,
-      // then the number of actual params can be [n-1, ...)
-      int lastIndex = methodParamSize - 1;
-      if (lastIndex >= 0
-          && parameters[lastIndex].isVarArgs()
-          && actualParamSize >= lastIndex) {
-
-        Class<?> type = parameters[lastIndex].getType().getComponentType();
-        actualParams[lastIndex] = buildVarargParam(paramsNode, lastIndex, type);
-        // We have handled the last param, no need to handle it later
-        --methodParamSize;
-      } else {
-        throw new IllegalArgumentException(
-            "Parameters number doesn't match. Expected: "
-                + methodParamSize + ". Got: " + paramsNode.size());
-      }
+    int lastIndex = methodParamSize - 1;
+
+    // If a methods has n params and the last one is a vararg,
+    // then the number of actual params must be in range [n-1, ...)
+    if (lastIndex >= 0 && parameters[lastIndex].isVarArgs() && actualParamSize >= lastIndex) {
+      Class<?> type = parameters[lastIndex].getType().getComponentType();
+      actualParams[lastIndex] = buildVarargParam(paramsNode, lastIndex, type);
+      // We have handled the last param, no need to handle it later
+      --methodParamSize;
+    } else if (methodParamSize != actualParamSize) {
+      throw new IllegalArgumentException(
+          "Parameters number doesn't match. Expected: "
+              + methodParamSize + ". Got: " + paramsNode.size());
     }
 
     for (int i = 0; i < methodParamSize; i++) {

ovsdb-client/src/test/java/com/vmware/ovsdb/service/OvsdbClientTest.java

@@ -613,6 +613,22 @@ private void testEcho() {
     } catch (InterruptedException | ExecutionException | TimeoutException e) {
       fail(e.getMessage());
     }
+
+    CompletableFuture<Void> successFuture3 = new CompletableFuture<>();
+    final String expectedResponse3 = "{\"result\":[\"inactivity probe\"]," + "\"error\":null,"
+        + "\"id\":\"echo\"}";
+    ovsdbServerEmulator.registerReadCallback(msg -> {
+      if (msg.equals(expectedResponse3)) {
+        successFuture3.complete(null);
+      }
+    });
+    ovsdbServerEmulator.write("{\"method\":\"echo\",\"params\":[\"inactivity probe\"],"
+        + "\"id\":\"echo\"}");
+    try {
+      successFuture3.get(VERIFY_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
+    } catch (InterruptedException | ExecutionException | TimeoutException e) {
+      fail(e.getMessage());
+    }
   }
 
   private void testInvalidJsonRpcMessage() throws OvsdbClientException, IOException {