improve wall filter

src/main/java/com/alibaba/druid/sql/ast/expr/SQLIdentifierExpr.java

@@ -25,15 +25,16 @@ public class SQLIdentifierExpr extends SQLExprImpl implements SQLName {
 
     private String            name;
 
+    private transient String  lowerName;
+
     public SQLIdentifierExpr(){
 
     }
 
     public SQLIdentifierExpr(String name){
-
         this.name = name;
     }
-    
+
     public String getSimleName() {
         return name;
     }
@@ -44,6 +45,18 @@ public class SQLIdentifierExpr extends SQLExprImpl implements SQLName {
 
     public void setName(String name) {
         this.name = name;
+        this.lowerName = null;
+    }
+
+    public String getLowerName() {
+        if (lowerName == null && name != null) {
+            lowerName = name.toLowerCase();
+        }
+        return lowerName;
+    }
+
+    public void setLowerName(String lowerName) {
+        this.lowerName = lowerName;
     }
 
     public void output(StringBuffer buf) {

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlLexer.java

@@ -357,6 +357,10 @@ public class MySqlLexer extends Lexer {
             }
 
             for (;;) {
+                if (ch == EOI) {
+                    this.token = Token.ERROR;
+                    return;
+                }
                 if (ch == '*' && charAt(pos + 1) == '/') {
                     bufPos += 2;
                     scanChar();

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -189,7 +189,8 @@ public class MySqlStatementParser extends SQLStatementParser {
     }
 
     public SQLSelectStatement parseSelect() {
-        return new SQLSelectStatement(new MySqlSelectParser(this.exprParser).select());
+        MySqlSelectParser selectParser = new MySqlSelectParser(this.exprParser);
+        return new SQLSelectStatement(selectParser.select());
     }
 
     public SQLUpdateStatement parseUpdateStatement() {