hws.core.Shared.java Source code

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Here is the source code for hws.core.Shared.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 hws.core;

import java.util.concurrent.TimeUnit;

//import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.binary.StringUtils;

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.exception.ZkInterruptedException;

/**
 * {@link Shared} area for stubs of a particular stream channel.
 * The shared area is implemented as a collection of key-value pairs, where the value can be any non-null object.
 */
public class Shared {
    private ZkClient zk;
    private String znodeBase;

    Shared(ZkClient zk, String znodeBase) {
        this.zk = zk;
        this.znodeBase = znodeBase;
        if (!this.zk.exists(znodeBase)) {
            this.zk.createPersistent(znodeBase);
        }
        this.znodeBase = this.znodeBase + "/";
    }

    private String encodeKey(String key) {
        return key;
    }

    /**
     * Creates or updates the value of a key-value pair.
     * @param key the key associated with the shared data specified by value.
     * @param value the value associated with the specified key.
     */
    public void set(String key, Object val) {
        if (val == null)
            throw new NullPointerException();
        this.zk.createPersistent(znodeBase + encodeKey(key), val);
    }

    /**
     * Returns the value associated with key.
     * @param key the key associated with the shared data required.
     */
    public <T extends Object> T get(String key) {
        return this.zk.readData(znodeBase + encodeKey(key), true);
    }

    /**
     * Waits for a key to exists. When the key happens to exist, the value associated with the key will be returned.
     * @param key the key associated with the shared data required.
     */
    public <T extends Object> T wait(String key) {
        String znode = znodeBase + encodeKey(key);
        this.zk.waitUntilExists(znode, TimeUnit.MILLISECONDS, 250);
        return get(key);
    }

}