mysql select * frm aaa limit 20xxx ，limit后的字符串无法转换为数字的处理

src/main/java/com/alibaba/druid/util/StringUtils.java

@@ -95,7 +95,7 @@ public class StringUtils {
         return a.equalsIgnoreCase(b);
     }
 
-    public static boolean isEmpty(String value) {
+    public static boolean isEmpty(CharSequence value) {
         if (value == null || value.length() == 0) {
             return true;
         }
@@ -119,4 +119,18 @@ public class StringUtils {
         }
         return h;
     }
+
+    public static boolean isNumeric(final CharSequence cs) {
+        if (isEmpty(cs)) {
+            return false;
+        }
+        final int sz = cs.length();
+        for (int i = 0; i < sz; i++) {
+            if (!Character.isDigit(cs.charAt(i))) {
+                return false;
+            }
+        }
+        return true;
+    }
+
 }