sql eval support

src/main/java/com/alibaba/druid/sql/dialect/mysql/visitor/MySqlEvalVisitorImpl.java

@@ -0,0 +1,53 @@
+package com.alibaba.druid.sql.dialect.mysql.visitor;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.alibaba.druid.sql.ast.expr.SQLBinaryOpExpr;
+import com.alibaba.druid.sql.ast.expr.SQLCharExpr;
+import com.alibaba.druid.sql.ast.expr.SQLVariantRefExpr;
+import com.alibaba.druid.sql.visitor.SQLEvalVisitor;
+import com.alibaba.druid.sql.visitor.SQLEvalVisitorUtils;
+
+public class MySqlEvalVisitorImpl extends MySqlASTVisitorAdapter implements SQLEvalVisitor {
+
+    private List<Object> parameters   = new ArrayList<Object>();
+
+    private int          variantIndex = -1;
+
+    public MySqlEvalVisitorImpl(){
+        this(new ArrayList<Object>(1));
+    }
+
+    public MySqlEvalVisitorImpl(List<Object> parameters){
+        this.parameters = parameters;
+    }
+
+    public List<Object> getParameters() {
+        return parameters;
+    }
+
+    public void setParameters(List<Object> parameters) {
+        this.parameters = parameters;
+    }
+
+    public boolean visit(SQLCharExpr x) {
+        return SQLEvalVisitorUtils.visit(this, x);
+    }
+
+    public int incrementAndGetVariantIndex() {
+        return ++variantIndex;
+    }
+
+    public int getVariantIndex() {
+        return variantIndex;
+    }
+
+    public boolean visit(SQLVariantRefExpr x) {
+        return SQLEvalVisitorUtils.visit(this, x);
+    }
+    
+    public boolean visit(SQLBinaryOpExpr x) {
+        return SQLEvalVisitorUtils.visit(this, x);
+    }
+}