eagle-core/eagle-alert-parent/eagle-alert-service/src/main/java/org/apache/eagle/service/alert/resolver/AttributeResolverFactory.java

/*
 * 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.eagle.service.alert.resolver;

import org.apache.eagle.metadata.service.ApplicationEntityService;
import com.typesafe.config.Config;

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

/**
 * @since 6/16/15.
 */
public final class AttributeResolverFactory {
    private static final Map<String, AttributeResolvable> fieldResolvableCache = Collections.synchronizedMap(new HashMap<>());

    public static AttributeResolvable getAttributeResolver(String fieldResolverName,
                                                           ApplicationEntityService entityService,
                                                           Config eagleServerConfig) throws AttributeResolveException {
        AttributeResolvable instance;
        if (fieldResolvableCache.containsKey(fieldResolverName)) {
            instance = fieldResolvableCache.get(fieldResolverName);
        } else {
            try {
                instance = (AttributeResolvable) Class.forName(fieldResolverName)
                    .getConstructor(ApplicationEntityService.class, Config.class)
                    .newInstance(entityService, eagleServerConfig);
                fieldResolvableCache.put(fieldResolverName, instance);
            } catch (ClassNotFoundException e) {
                throw new AttributeResolveException("Attribute Resolver in type of " + fieldResolverName + " is not found", e);
            } catch (InstantiationException | IllegalAccessException e) {
                throw new AttributeResolveException(e);
            } catch (Exception ex) {
                throw new AttributeResolveException(ex);
            }
        }
        return instance;
    }
}