org.mybatis.dynamic.sql.select.aggregate.AbstractAggregate Maven / Gradle / Ivy
/**
* Copyright 2016-2018 the original author or authors.
*
* Licensed 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.mybatis.dynamic.sql.select.aggregate;
import java.util.Objects;
import java.util.Optional;
import org.mybatis.dynamic.sql.BasicColumn;
import org.mybatis.dynamic.sql.render.TableAliasCalculator;
/**
* This class is the base class for aggregate functions.
*
* @author Jeff Butler
*
* @param the subclass type
*/
public abstract class AbstractAggregate> implements BasicColumn {
protected BasicColumn column;
protected String alias;
protected AbstractAggregate(BasicColumn column) {
this.column = Objects.requireNonNull(column);
}
@Override
public Optional alias() {
return Optional.ofNullable(alias);
}
@Override
public String renderWithTableAlias(TableAliasCalculator tableAliasCalculator) {
return render(column.renderWithTableAlias(tableAliasCalculator));
}
@Override
public T as(String alias) {
T copy = copy();
copy.alias = alias;
return copy;
}
protected abstract T copy();
/**
* Calculate the rendered string for the select list.
*
* @param columnName the calculated column name. It will have the table alias already applied
* if applicable.
* @return the rendered string for the select list
*/
protected abstract String render(String columnName);
}