Redis缓存Object，List对象

一、到目前为止（jedis-2.2.0.jar），在Jedis中其实并没有提供这样的API对对象，或者是List对象的直接缓存，即并没有如下类似的API

jedis.set(String key, Object value)

jedis.set(String key, List<M> values)

而更多的API是类似于 jedis.set(String key, String value)或者jedis.set(String key, String ... value)

那如果我们想缓存对象，怎么办呢？

二、通过研究Jedis的API，我们发现其提供了这样的API

jedis.set(byte[], byte[]),

通过这个API，很显然我们能够实现

jedis.set(String key, Object value)

jedis.set(String key, List<M> values)

我们需要关注的就是在cache的时候将Object和List对象转换成字节数组并且需要提供将字节数组转换成对象返回。

三、考虑到扩展性，设计了3个类，抽象父类SerializeTranscoder， 子类ListTranscoder和ObjectsTranscoder 以及一个Unit test 类 用于模拟对象，list对象和字节数组的转换，即Serialize和de-searilize的过程。

1. SerializeTranscoder

package com.chuanliu.platform.activity.basic.util.serialize;

import java.io.Closeable;

import org.apache.log4j.Logger;


/**
 * @author Josh Wang(Sheng)
 *
 * @email  [e-mail]
 */
public abstract class SerializeTranscoder {

  protected static Logger logger = Logger.getLogger(SerializeTranscoder.class);
  
  public abstract byte[] serialize(Object value);
  
  public abstract Object deserialize(byte[] in);
  
  public void close(Closeable closeable) {
    if (closeable != null) {
      try {
        closeable.close();
      } catch (Exception e) {
         logger.info("Unable to close " + closeable, e); 
      }
    }
  }
}

2. ListTranscoder

package com.chuanliu.platform.activity.basic.util.serialize;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import com.chuanliu.platform.activity.basic.util.LoggerUtils;


/**
 * Case 1.
 * Jedis does not support cache the Object directly, the Objects needed to be 
 * serialized and de-serialized
 * 
 * Case 2.
 * coming very soon...
 * 
 * @author Josh Wang(Sheng)
 *
 * @email  [e-mail]
 */
public class ListTranscoder<M extends Serializable> extends SerializeTranscoder {
  
  @SuppressWarnings("unchecked")
  public List<M> deserialize(byte[] in) {
    List<M> list = new ArrayList<>();
    ByteArrayInputStream bis = null;
    ObjectInputStream is = null;
    try {
      if (in != null) {
        bis = new ByteArrayInputStream(in);
        is = new ObjectInputStream(bis);
        while (true) {
          M m = (M)is.readObject();
          if (m == null) {
            break;
          }
          
          list.add(m);
          
        }
        is.close();
        bis.close();
      }
    } catch (IOException e) {  
      LoggerUtils.error(logger, String.format("Caught IOException decoding %d bytes of data",  
        in == null ? 0 : in.length) + e);  
  } catch (ClassNotFoundException e) {  
      LoggerUtils.error(logger, String.format("Caught CNFE decoding %d bytes of data",  
        in == null ? 0 : in.length) + e);  
  }  finally {
      close(is);
      close(bis);
    }
    
    return  list;
  }
  

  @SuppressWarnings("unchecked")
  @Override
  public byte[] serialize(Object value) {
    if (value == null)
      throw new NullPointerException("Can't serialize null");
    
    List<M> values = (List<M>) value;
    
    byte[] results = null;
    ByteArrayOutputStream bos = null;
    ObjectOutputStream os = null;
    
    try {
      bos = new ByteArrayOutputStream();
      os = new ObjectOutputStream(bos);
      for (M m : values) {
        os.writeObject(m);
      }
      
      // os.writeObject(null);
      os.close();
      bos.close();
      results = bos.toByteArray();
    } catch (IOException e) {
      throw new IllegalArgumentException("Non-serializable object", e);
    } finally {
      close(os);
      close(bos);
    }