CustomFunctionExtension.java

/*
 * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
 *
 * 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.wso2.siddhi.sample.util;

import org.wso2.siddhi.core.config.ExecutionPlanContext;
import org.wso2.siddhi.core.exception.ExecutionPlanCreationException;
import org.wso2.siddhi.core.executor.ExpressionExecutor;
import org.wso2.siddhi.core.executor.function.FunctionExecutor;
import org.wso2.siddhi.query.api.definition.Attribute;

public class CustomFunctionExtension extends FunctionExecutor {

    private Attribute.Type returnType;

    /**
     * The initialization method for FunctionExecutor, this method will be called before the other methods
     *
     * @param attributeExpressionExecutors are the executors of each function parameters
     * @param executionPlanContext         the context of the execution plan
     */
    @Override
    protected void init(ExpressionExecutor[] attributeExpressionExecutors, ExecutionPlanContext executionPlanContext) {
        for (ExpressionExecutor expressionExecutor : attributeExpressionExecutors) {
            Attribute.Type attributeType = expressionExecutor.getReturnType();
            if (attributeType == Attribute.Type.DOUBLE) {
                returnType = attributeType;

            } else if ((attributeType == Attribute.Type.STRING) || (attributeType == Attribute.Type.BOOL)) {
                throw new ExecutionPlanCreationException("Plus cannot have parameters with types String or Bool");
            } else {
                returnType = Attribute.Type.LONG;
            }
        }
    }

    /**
     * The main execution method which will be called upon event arrival
     * when there are more then one function parameter
     *
     * @param data the runtime values of function parameters
     * @return the function result
     */
    @Override
    protected Object execute(Object[] data) {
        if (returnType == Attribute.Type.DOUBLE) {
            double total = 0;
            for (Object aObj : data) {
                total += Double.parseDouble(String.valueOf(aObj));
            }

            return total;
        } else {
            long total = 0;
            for (Object aObj : data) {
                total += Long.parseLong(String.valueOf(aObj));
            }
            return total;
        }
    }

    /**
     * The main execution method which will be called upon event arrival
     * when there are zero or one function parameter
     *
     * @param data null if the function parameter count is zero or
     *             runtime data value of the function parameter
     * @return the function result
     */
    @Override
    protected Object execute(Object data) {
        if (returnType == Attribute.Type.DOUBLE) {
            return Double.parseDouble(String.valueOf(data));
        } else {
            return Long.parseLong(String.valueOf(data));
        }
    }

    /**
     * This will be called only once and this can be used to acquire
     * required resources for the processing element.
     * This will be called after initializing the system and before
     * starting to process the events.
     */
    @Override
    public void start() {

    }

    /**
     * This will be called only once and this can be used to release
     * the acquired resources for processing.
     * This will be called before shutting down the system.
     */
    @Override
    public void stop() {

    }

    @Override
    public Attribute.Type getReturnType() {
        return returnType;
    }

    /**
     * Used to collect the serializable state of the processing element, that need to be
     * persisted for the reconstructing the element to the same state on a different point of time
     *
     * @return stateful objects of the processing element as an array
     */
    @Override
    public Object[] currentState() {
        return new Object[0];
    }

    /**
     * Used to restore serialized state of the processing element, for reconstructing
     * the element to the same state as if was on a previous point of time.
     *
     * @param state the stateful objects of the element as an array on
     *              the same order provided by currentState().
     */
    @Override
    public void restoreState(Object[] state) {

    }

}