improve wall filter

src/main/java/com/alibaba/druid/sql/parser/Lexer.java

@@ -68,10 +68,20 @@ public class Lexer {
 
     private int            varIndex     = -1;
 
+    protected CommentHandler commentHandler;
+
     public Lexer(String input){
         this(input, true);
     }
 
+    public CommentHandler getCommentHandler() {
+        return commentHandler;
+    }
+
+    public void setCommentHandler(CommentHandler commentHandler) {
+        this.commentHandler = commentHandler;
+    }
+
     public final char charAt(int index) {
         if (index >= text.length()) {
             return EOI;
@@ -1008,4 +1018,9 @@ public class Lexer {
     public BigDecimal decimalValue() {
         return new BigDecimal(text.toCharArray(), mark, bufPos);
     }
+
+    public static interface CommentHandler {
+
+        boolean handle(Token lastToken, String comment);
+    }
 }