io.atlasmap.core.DefaultAtlasFunctionResolver Maven / Gradle / Ivy

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/**
 * Copyright (C) 2017 Red Hat, Inc.
 * 
 * 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 io.atlasmap.core;

import java.util.HashMap;
import java.util.List;
import java.util.ServiceLoader;

import io.atlasmap.expression.Expression;
import io.atlasmap.expression.FunctionResolver;
import io.atlasmap.expression.parser.ParseException;
import io.atlasmap.spi.FunctionFactory;

public class DefaultAtlasFunctionResolver implements FunctionResolver {
    
    private static DefaultAtlasFunctionResolver instance;

    private HashMap functions = new HashMap<>();

    public static DefaultAtlasFunctionResolver getInstance() {
        if (instance == null) {
            instance = new DefaultAtlasFunctionResolver();
            instance.init();
        }
        return instance;
    }

    private void init() {
        functions = new HashMap<>();
        ServiceLoader implementations = ServiceLoader.load(FunctionFactory.class, FunctionFactory.class.getClassLoader());
        for (FunctionFactory f : implementations) {
            functions.put(f.getName().toUpperCase(), f);
        }
    }

    @Override
    public Expression resolve(String name, List args) throws ParseException {
        name = name.toUpperCase();
        FunctionFactory f = functions.get(name);
        if (f != null) {
            return f.create(args);
        }

        throw new IllegalArgumentException(String.format("The expression function '%s' was not found", name));
    }

}