[fit] Retrieve the first non-null exception message from the exception chain. (#176)

Author: surpercodehang

framework/fit/java/fit-util/src/main/java/modelengine/fitframework/util/ExceptionUtils.java

@@ -55,7 +55,7 @@ public static Throwable getActualCause(MethodInvocationException exception) {
     /**
      * 获取异常的原因。
      *
-     * @param throwable 表示指定异常的 {@link Exception}。
+     * @param throwable 表示指定异常的 {@link Throwable}。
      * @return 表示异常原因的 {@link String}。
      */
     public static String getReason(Throwable throwable) {
@@ -64,4 +64,23 @@ public static String getReason(Throwable throwable) {
         }
         return throwable.getClass().getSimpleName() + ": " + throwable.getMessage();
     }
+
+    /**
+     * 获取从异常链中找出第一个非空的异常消息。
+     *
+     * @param throwable 表示指定异常的 {@link Throwable}。
+     * @return 表示异常原因的 {@link String}。
+     */
+    public static String getActualMessage(Throwable throwable) {
+        Set<Throwable> visited = new HashSet<>();
+        while (throwable != null && !visited.contains(throwable)) {
+            visited.add(throwable);
+            String message = throwable.getMessage();
+            if (StringUtils.isNotBlank(message)) {
+                return message;
+            }
+            throwable = throwable.getCause();
+        }
+        return null;
+    }
 }

framework/fit/java/fit-util/src/test/java/modelengine/fitframework/util/ExceptionUtilsTest.java

@@ -106,4 +106,43 @@ void givenExceptionCauseHasAnotherTypeCauseThenGetItsDescendantsCause() {
             assertThat(actualCause).isNotNull().hasMessage("error");
         }
     }
+
+    @Nested
+    @DisplayName("test getActualMessage(Throwable throwable)")
+    class WhenGetActualMessage {
+        @Test
+        @DisplayName("when throwable has non-blank message, return the message")
+        void givenThrowableWithMessageThenReturnMessage() {
+            Throwable throwable = new Exception("Error occurred");
+            String message = ExceptionUtils.getActualMessage(throwable);
+            assertThat(message).isEqualTo("Error occurred");
+        }
+
+        @Test
+        @DisplayName("when throwable chain has non-blank message in deep cause, return the first valid message")
+        void givenDeepThrowableChainThenReturnFirstValidMessage() {
+            Throwable cause = new Exception("Root cause");
+            Throwable throwable = new Exception(null, new Exception("   ", cause));
+            String message = ExceptionUtils.getActualMessage(throwable);
+            assertThat(message).isEqualTo("Root cause");
+        }
+
+        @Test
+        @DisplayName("when throwable chain has all blank messages, return null")
+        void givenAllBlankMessagesThenReturnNull() {
+            Throwable throwable = new Exception(null, new Exception("   "));
+            String message = ExceptionUtils.getActualMessage(throwable);
+            assertThat(message).isNull();
+        }
+
+        @Test
+        @DisplayName("when throwable chain has circular reference, return valid message")
+        void givenCircularReferenceThenReturnFirstValidMessage() {
+            Exception e1 = new Exception("e1");
+            Exception e2 = new Exception("e2", e1);
+            e1.initCause(e2);
+            assertThat(ExceptionUtils.getActualMessage(e1)).isEqualTo("e1");
+            assertThat(ExceptionUtils.getActualMessage(e2)).isEqualTo("e2");
+        }
+    }
 }