org.apache.tajo.ws.rs.resources.outputs.RestOutputFactory.java Source code

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Here is the source code for org.apache.tajo.ws.rs.resources.outputs.RestOutputFactory.java

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/**
 * 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.tajo.ws.rs.resources.outputs;

import com.google.common.collect.Maps;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.tajo.master.exec.NonForwardQueryResultScanner;
import org.apache.tajo.util.ClassUtil;
import org.apache.tajo.ws.rs.annotation.RestReturnType;

import java.lang.reflect.Modifier;
import java.util.Map;
import java.util.Set;

public class RestOutputFactory {
    private static Log LOG = LogFactory.getLog(RestOutputFactory.class);
    private static Map<String, String> restOutputClasses = load();

    private static Map<String, String> load() {
        Map<String, String> outputClasses = Maps.newHashMap();
        Set<Class> restOutputClasses = ClassUtil.findClasses(AbstractStreamingOutput.class,
                "org.apache.tajo.ws.rs.resources.outputs");

        for (Class eachClass : restOutputClasses) {
            if (eachClass.isInterface() || Modifier.isAbstract(eachClass.getModifiers())) {
                continue;
            }

            AbstractStreamingOutput streamingOutput = null;
            try {
                streamingOutput = (AbstractStreamingOutput) eachClass
                        .getDeclaredConstructor(
                                new Class[] { NonForwardQueryResultScanner.class, Integer.class, Integer.class })
                        .newInstance(null, 0, 0);
            } catch (Exception e) {
                LOG.warn(eachClass + " cannot instantiate Function class because of " + e.getMessage(), e);
                continue;
            }
            String className = streamingOutput.getClass().getCanonicalName();
            String headerType = streamingOutput.getClass().getAnnotation(RestReturnType.class).mimeType();

            if (StringUtils.isNotEmpty(headerType)) {
                outputClasses.put(headerType, className);
            }
        }

        return outputClasses;
    }

    public static AbstractStreamingOutput get(String mimeType, NonForwardQueryResultScanner scanner, Integer count,
            Integer startOffset) {
        AbstractStreamingOutput output = null;
        try {
            if (restOutputClasses.containsKey(mimeType)) {
                String className = (String) restOutputClasses.get(mimeType);
                Class<?> clazz = Class.forName(className);
                output = (AbstractStreamingOutput) clazz
                        .getDeclaredConstructor(
                                new Class[] { NonForwardQueryResultScanner.class, Integer.class, Integer.class })
                        .newInstance(scanner, count, startOffset);
            } else {
                output = new CSVStreamingOutput(scanner, count, startOffset);
            }
        } catch (Exception eh) {
            LOG.error(eh);
        }

        return output;
    }
}