org.apache.flink.table.expressions.ExpressionDefaultVisitor Maven / Gradle / Ivy

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.expressions;

import org.apache.flink.annotation.Internal;

/**
 * Implementation of {@link ExpressionVisitor} that redirects all calls to {@link
 * #defaultMethod(Expression)}.
 */
@Internal
public abstract class ExpressionDefaultVisitor implements ExpressionVisitor {

    @Override
    public T visit(CallExpression call) {
        return defaultMethod(call);
    }

    @Override
    public T visit(ValueLiteralExpression valueLiteral) {
        return defaultMethod(valueLiteral);
    }

    @Override
    public T visit(FieldReferenceExpression fieldReference) {
        return defaultMethod(fieldReference);
    }

    @Override
    public T visit(TypeLiteralExpression typeLiteral) {
        return defaultMethod(typeLiteral);
    }

    @Override
    public T visit(Expression other) {
        return defaultMethod(other);
    }

    protected abstract T defaultMethod(Expression expression);
}