Add RuntimeException converting method in BlockException and polish logic for validation

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-core/src/main/java/com/alibaba/csp/sentinel/slots/block/BlockException.java

@@ -23,7 +23,11 @@ package com.alibaba.csp.sentinel.slots.block;
  */
 public abstract class BlockException extends Exception {
 
+    private static final int MAX_SEARCH_DEPTH = 10;
+
     public static final String BLOCK_EXCEPTION_FLAG = "SentinelBlockException";
+    public static final String BLOCK_EXCEPTION_MSG_PREFIX = "SentinelBlockException: ";
+
     /**
      * <p>this constant RuntimeException has no stack trace, just has a message
      * {@link #BLOCK_EXCEPTION_FLAG} that marks its name.
@@ -85,12 +89,18 @@ public abstract class BlockException extends Exception {
         this.ruleLimitApp = ruleLimitApp;
     }
 
+    public RuntimeException toRuntimeException() {
+        RuntimeException t = new RuntimeException(BLOCK_EXCEPTION_MSG_PREFIX + getClass().getSimpleName());
+        t.setStackTrace(sentinelStackTrace);
+        return t;
+    }
+
     /**
      * Check whether the exception is sentinel blocked exception. One exception is sentinel blocked
      * exception only when:
      * <ul>
      * <li>the exception or its (sub-)cause is {@link BlockException}, or</li>
-     * <li>the exception's message is or any of its sub-cause's message equals to {@link #BLOCK_EXCEPTION_FLAG}</li>
+     * <li>the exception's message or any of its sub-cause's message is prefixed by {@link #BLOCK_EXCEPTION_FLAG}</li>
      * </ul>
      *
      * @param t the exception.
@@ -103,8 +113,11 @@ public abstract class BlockException extends Exception {
 
         int counter = 0;
         Throwable cause = t;
-        while (cause != null && counter++ < 50) {
-            if ((cause instanceof BlockException) || (BLOCK_EXCEPTION_FLAG.equals(cause.getMessage()))) {
+        while (cause != null && counter++ < MAX_SEARCH_DEPTH) {
+            if (cause instanceof BlockException) {
+                return true;
+            }
+            if (cause.getMessage() != null && cause.getMessage().startsWith(BLOCK_EXCEPTION_FLAG)) {
                 return true;
             }
             cause = cause.getCause();