Redis 存储List对象

      如果需要用到Redis存储List对象，而list又不需要进行操作，可以按照MC的方式进行存储，不过Jedis之类的客户端没有提供API，可以有两种思路实现：

1.      分别序列化 elements ,然后 set 存储

2.    序列化List对象，set存储

这两种方法都类似MC的 Object方法存储，运用这种方式意味着放弃Redis对List提供的操作方法。

import net.spy.memcached.compat.CloseUtil;
import net.spy.memcached.compat.log.Logger;
import net.spy.memcached.compat.log.LoggerFactory;
import redis.clients.jedis.Client;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

/**
 * Created by IntelliJ IDEA.
 * User: lifeng.xu
 * Date: 12-6-11
 * Time: 上午11:10
 * To change this template use File | Settings | File Templates.
 */
public class JedisTest {

    private static Logger logger = LoggerFactory.getLogger(JedisTest.class);

    /**
     * Jedis Pool for Jedis Resource
     * @return
     */
    public static JedisPool buildJedisPool(){
        JedisPoolConfig config = new JedisPoolConfig();
        config.setMaxActive(1);
        config.setMinIdle(50);
        config.setMaxIdle(3000);
        config.setMaxWait(5000);
        JedisPool jedisPool = new JedisPool(config,
                "*****", ****);
        return jedisPool;
    }

    /**
     * Test Data
     * @return
     */
    public static List buildTestData(){
        User a = new User();
        a.setName("a");
        User b = new User();
        b.setName("b");
        List list = new ArrayList();
        list.add(a);
        list.add(b);
        return list;
    }

    /**
     * Test for
     */
    public static void testSetElements(){
        List testData = buildTestData();
        Jedis jedis = buildJedisPool().getResource();
        String key = "testSetElements" + new Random(1000).nextInt();
        jedis.set(key.getBytes(), ObjectsTranscoder.serialize(testData));

        //验证
        byte[] in = jedis.get(key.getBytes());
        List list = ObjectsTranscoder.deserialize(in);
        for(User user : list){
            System.out.println("testSetElements user name is:" + user.getName());
        }
    }

    public static void testSetEnsemble(){
        List testData = buildTestData();
        Jedis jedis = buildJedisPool().getResource();
        String key = "testSetEnsemble" + new Random(1000).nextInt();
        jedis.set(key.getBytes(), ListTranscoder.serialize(testData));

        //验证
        byte[] in = jedis.get(key.getBytes());
        List list = (List)ListTranscoder.deserialize(in);
        for(User user : list){
            System.out.println("testSetEnsemble user name is:" + user.getName());
        }
    }

    public static void main(String[] args) {
        testSetElements();
        testSetEnsemble();
    }

    public static void close(Closeable closeable) {
        if (closeable != null) {
            try {
                closeable.close();
            } catch (Exception e) {
                logger.info("Unable to close %s", closeable, e);
            }
        }
    }

    static class User implements Serializable{
        String name;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }
    }

    static class ObjectsTranscoder{
        
        public static byte[] serialize(List value) {
            if (value == null) {
                throw new NullPointerException("Can't serialize null");
            }
            byte[] rv=null;
            ByteArrayOutputStream bos = null;
            ObjectOutputStream os = null;
            try {
                bos = new ByteArrayOutputStream();
                os = new ObjectOutputStream(bos);
                for(User user : value){
                    os.writeObject(user);
                }
                os.writeObject(null);
                os.close();
                bos.close();
                rv = bos.toByteArray();
            } catch (IOException e) {
                throw new IllegalArgumentException("Non-serializable object", e);
            } finally {
                close(os);
                close(bos);
            }
            return rv;
        }

        public static List deserialize(byte[] in) {
            List list = new ArrayList();
            ByteArrayInputStream bis = null;
            ObjectInputStream is = null;
            try {
                if(in != null) {
                    bis=new ByteArrayInputStream(in);
                    is=new ObjectInputStream(bis);
                    while (true) {
                        User user = (User) is.readObject();
                        if(user == null){
                            break;
                        }else{
                            list.add(user);
                        }
                    }
                    is.close();
                    bis.close();
                }
            } catch (IOException e) {
                logger.warn("Caught IOException decoding %d bytes of data",
                        in == null ? 0 : in.length, e);
            } catch (ClassNotFoundException e) {
                logger.warn("Caught CNFE decoding %d bytes of data",
                        in == null ? 0 : in.length, e);
            } finally {
                CloseUtil.close(is);
                CloseUtil.close(bis);
            }
            return list;
        }
    }
    
    static class ListTranscoder{
        public static byte[] serialize(Object value) {
            if (value == null) {
                throw new NullPointerException("Can't serialize null");
            }
            byte[] rv=null;
            ByteArrayOutputStream bos = null;
            ObjectOutputStream os = null;
            try {
                bos = new ByteArrayOutputStream();
                os = new ObjectOutputStream(bos);
                os.writeObject(value);
                os.close();
                bos.close();
                rv = bos.toByteArray();
            } catch (IOException e) {
                throw new IllegalArgumentException("Non-serializable object", e);
            } finally {
                close(os);
                close(bos);
            }
            return rv;
        }

        public static Object deserialize(byte[] in) {
            Object rv=null;
            ByteArrayInputStream bis = null;
            ObjectInputStream is = null;
            try {
                if(in != null) {
                    bis=new ByteArrayInputStream(in);
                    is=new ObjectInputStream(bis);
                    rv=is.readObject();
                    is.close();
                    bis.close();
                }
            } catch (IOException e) {
                logger.warn("Caught IOException decoding %d bytes of data",
                        in == null ? 0 : in.length, e);
            } catch (ClassNotFoundException e) {
                logger.warn("Caught CNFE decoding %d bytes of data",
                        in == null ? 0 : in.length, e);
            } finally {
                CloseUtil.close(is);
                CloseUtil.close(bis);
            }
            return rv;
        }
    }
}

PS：Redsi中存储list没有封装对Object的API，是不是也是倾向于只存储用到的字段，而不是存储Object本身呢？Redis是一个In-Mem的产品，会觉得我们应用的方式。