org.mybatis.dynamic.sql.render.TableAliasCalculator Maven / Gradle / Ivy

/**
 *    Copyright 2016-2017 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.render;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;

import org.mybatis.dynamic.sql.SqlTable;

public class TableAliasCalculator {
    
    private Map aliases;

    protected TableAliasCalculator(Map aliases) {
        this.aliases = Objects.requireNonNull(aliases);
    }
    
    public Optional aliasForColumn(SqlTable table) {
        return Optional.ofNullable(aliases.get(table));
    }

    public Optional aliasForTable(SqlTable table) {
        return Optional.ofNullable(aliases.get(table));
    }
    
    public static TableAliasCalculator of(SqlTable table, String alias) {
        Map tableAliases = new HashMap<>();
        tableAliases.put(table, alias);
        return of(tableAliases);
    }
    
    public static TableAliasCalculator of(Map aliases) {
        return new TableAliasCalculator(aliases);
    }
    
    public static TableAliasCalculator empty() {
        return of(Collections.emptyMap());
    }
}