AXIS2-6104 Null-check getOpMethod, sanitize test data

- All four message receivers (gson + moshi, InOut + InOnly) now check
  for null return from getOpMethod() and throw a clear AxisFault with
  the operation name and service class, instead of NPE
- Replace proprietary department names in pagination test with generic
  "Department A" through "Department O"

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: robertlazarski

modules/json/src/org/apache/axis2/json/gson/rpc/JsonInOnlyRPCMessageReceiver.java

@@ -73,6 +73,10 @@ public void invokeService(JsonReader jsonReader, Object serviceObj, String opera
         Class implClass = serviceObj.getClass();
         Method[] allMethods = implClass.getDeclaredMethods();
         Method method = JsonUtils.getOpMethod(operation_name, allMethods);
+        if (method == null) {
+            throw new AxisFault("Operation '" + operation_name
+                    + "' not found on service class " + implClass.getName());
+        }
         Class[] paramClasses = method.getParameterTypes();
         try {
             int paramCount = paramClasses.length;

modules/json/src/org/apache/axis2/json/gson/rpc/JsonRpcMessageReceiver.java

@@ -75,6 +75,10 @@ public void invokeService(JsonReader jsonReader, Object serviceObj, String opera
         Class implClass = serviceObj.getClass();
         Method[] allMethods = implClass.getDeclaredMethods();
         Method method = JsonUtils.getOpMethod(operation_name, allMethods);
+        if (method == null) {
+            throw new AxisFault("Operation '" + operation_name
+                    + "' not found on service class " + implClass.getName());
+        }
         Class[] paramClasses = method.getParameterTypes();
         try {
             int paramCount = paramClasses.length;

modules/json/src/org/apache/axis2/json/moshi/rpc/JsonInOnlyRPCMessageReceiver.java

@@ -73,6 +73,10 @@ public void invokeService(JsonReader jsonReader, Object serviceObj, String opera
         Class implClass = serviceObj.getClass();
         Method[] allMethods = implClass.getDeclaredMethods();
         Method method = JsonUtils.getOpMethod(operation_name, allMethods);
+        if (method == null) {
+            throw new AxisFault("Operation '" + operation_name
+                    + "' not found on service class " + implClass.getName());
+        }
         Class[] paramClasses = method.getParameterTypes();
         try {
             int paramCount = paramClasses.length;

modules/json/src/org/apache/axis2/json/moshi/rpc/JsonRpcMessageReceiver.java

@@ -75,6 +75,10 @@ public void invokeService(JsonReader jsonReader, Object serviceObj, String opera
         Class implClass = serviceObj.getClass();
         Method[] allMethods = implClass.getDeclaredMethods();
         Method method = JsonUtils.getOpMethod(operation_name, allMethods);
+        if (method == null) {
+            throw new AxisFault("Operation '" + operation_name
+                    + "' not found on service class " + implClass.getName());
+        }
         Class[] paramClasses = method.getParameterTypes();
         try {
             int paramCount = paramClasses.length;

modules/json/test/org/apache/axis2/json/rpc/PaginatedResponseTest.java

@@ -337,10 +337,10 @@ public void testEnterprise_unpaginated_smallLookupTable() {
         // Scenario: a lookup/reference table (e.g. list of 15 departments).
         // No pagination needed — return the full set with hasMore=false.
         List<String> departments = Arrays.asList(
-                "Equity Long/Short", "Fixed Income", "Macro", "Quant",
-                "Event Driven", "Multi-Strategy", "Credit", "Real Assets",
-                "Private Equity", "Venture", "Commodities", "FX",
-                "Emerging Markets", "Infrastructure", "Insurance-Linked");
+                "Department A", "Department B", "Department C", "Department D",
+                "Department E", "Department F", "Department G", "Department H",
+                "Department I", "Department J", "Department K", "Department L",
+                "Department M", "Department N", "Department O");
 
         PaginatedResponse<String> resp = PaginatedResponse.unpaginated(departments);