eagle-core/eagle-query/eagle-query-base/src/main/java/org/apache/eagle/query/aggregate/raw/WritableList.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.query.aggregate.raw;

import org.apache.hadoop.io.Writable;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.lang.reflect.ParameterizedType;
import java.util.ArrayList;

/**
 * @since : 11/6/14,2014
 */
public class WritableList<E extends Writable> extends ArrayList<E> implements Writable {
    private Class<E> itemTypeClass;

    public WritableList(Class<E> typeClass) {
        this.itemTypeClass = typeClass;
    }

    public WritableList(Class<E> typeClass,int initialCapacity) {
        super(initialCapacity);
        this.itemTypeClass = typeClass;
    }


    /**
     * <h3> Get item class by </h3>
     */
    @Deprecated
    public WritableList() {
        this.itemTypeClass = (Class<E>) ((ParameterizedType)getClass().getGenericSuperclass()).getActualTypeArguments()[0];
    }

    private void check() throws IOException {
        if (this.itemTypeClass == null) {
            throw new IOException("Class Type of WritableArrayList<E extends Writable> is null");
        }
    }

    public Class<E> getItemClass() {
        return itemTypeClass;
    }

    /**
     * Serialize the fields of this object to <code>out</code>.
     *
     * @param out <code>DataOuput</code> to serialize this object into.
     * @throws java.io.IOException
     */
    @Override
    public void write(DataOutput out) throws IOException {
        this.check();
        out.writeInt(this.size());
        for (Writable item: this) {
            item.write(out);
        }
    }

    /**
     * Deserialize the fields of this object from <code>in</code>.
     * <p/>
     * <p>For efficiency, implementations should attempt to re-use storage in the
     * existing object where possible.</p>
     *
     * @param in <code>DataInput</code> to deseriablize this object from.
     * @throws java.io.IOException
     */
    @Override
    public void readFields(DataInput in) throws IOException {
        this.check();
        int size = in.readInt();
        for (int i = 0; i < size; i++) {
            try {
                E item = itemTypeClass.newInstance();
                item.readFields(in);
                this.add(item);
            } catch (InstantiationException e) {
                throw new IOException("Got exception to create instance for class: " + itemTypeClass + ": " + e.getMessage(), e);
            } catch (IllegalAccessException e) {
                throw new IOException("Got exception to create instance for class: " + itemTypeClass + ": " + e.getMessage(), e);
            }
        }
    }
}