Play 缓存插件 --Cache

Cache是个抽象的类，有两个继承的类EhCacheImpl（默认）和MemcachedImpl
- 初始化,在第一次请求时init()，Cache.init()

有两个属性public static CacheImpl cacheImpl;public static CacheImpl forcedCacheImpl;

public static void init() {     if(forcedCacheImpl != null) {         cacheImpl = forcedCacheImpl;         return;     }     if (Play.configuration.getProperty("memcached", "disabled").equals("enabled")) {            try {                cacheImpl = MemcachedImpl.getInstance(true);            } catch (Exception e) {                cacheImpl = EhCacheImpl.newInstance();            }        } else {            cacheImpl = EhCacheImpl.newInstance();        } }

• 基本的一些操作

Cache

 public static void add(String key, Object value, String expiration) {        checkSerializable(value);        cacheImpl.add(key, value, Time.parseDuration(expiration));    }    public static boolean safeAdd(String key, Object value, String expiration) {        checkSerializable(value);        return cacheImpl.safeAdd(key, value, Time.parseDuration(expiration));    }    public static void add(String key, Object value) {        checkSerializable(value);        cacheImpl.add(key, value, Time.parseDuration(null));    }     public static void set(String key, Object value, String expiration) {        checkSerializable(value);        cacheImpl.set(key, value, Time.parseDuration(expiration));    }....

下面来重点讲下EnCacheImpl
属性
private static EhCacheImpl uniqueInstance;
net.sf.ehcache.CacheManager cacheManager;
net.sf.ehcache.Cache cache;
private static final String cacheName = “play”;
//单列模式

 初始化 private EhCacheImpl() {      this.cacheManager = CacheManager.create();      this.cacheManager.addCache(cacheName);      this.cache = cacheManager.getCache(cacheName);  }public static EhCacheImpl newInstance() {    uniqueInstance = new EhCacheImpl();     return uniqueInstance; }

• 基本的操作

public void add(String key, Object value, int expiration) {        if (cache.get(key) != null) {            return;        }        Element element = new Element(key, value);        element.setTimeToLive(expiration);        cache.put(element);    }    public void clear() {        cache.removeAll();    }    public synchronized long decr(String key, int by) {        Element e = cache.get(key);        if (e == null) {            return -1;        }        long newValue = ((Number) e.getValue()).longValue() - by;        Element newE = new Element(key, newValue);        newE.setTimeToLive(e.getTimeToLive());        cache.put(newE);        return newValue;    }    public void delete(String key) {        cache.remove(key);    }

下面来重点讲解下MemcachedImpl
private static MemcachedImpl uniqueInstance;
net.spy.memcached.MemcachedClient client;
net.spy.memcached.transcoders.SerializingTranscoder tc;

初始化 public static MemcachedImpl getInstance(boolean forceClientInit) throws IOException {        if (uniqueInstance == null) {            uniqueInstance = new MemcachedImpl();        } else if (forceClientInit) {            Thread.interrupted();            uniqueInstance.initClient();        }        return uniqueInstance;    }

• 初始化

  序列化和反序列化

private MemcachedImpl() throws IOException {        tc = new SerializingTranscoder() {            protected Object deserialize(byte[] data) {                try {                    return new ObjectInputStream(new ByteArrayInputStream(data)) {                        protected Class<?> resolveClass(ObjectStreamClass desc)                                throws IOException, ClassNotFoundException {                            return Class.forName(desc.getName(), false, Play.classloader);                        }                    }.readObject();                } catch (Exception e) {                    Logger.error(e, "Could not deserialize");                }                return null;            }            protected byte[] serialize(Object object) {                try {                    ByteArrayOutputStream bos = new ByteArrayOutputStream();                    new ObjectOutputStream(bos).writeObject(object);                    return bos.toByteArray();                } catch (IOException e) {                    Logger.error(e, "Could not serialize");                }                return null;            }        };        initClient();    }

创建客户端

    public void initClient() throws IOException {        System.setProperty("net.spy.log.LoggerImpl", "net.spy.memcached.compat.log.Log4JLogger");        List<InetSocketAddress> addrs;        if (Play.configuration.containsKey("memcached.host")) {            addrs = AddrUtil.getAddresses(Play.configuration.getProperty("memcached.host"));        } else if (Play.configuration.containsKey("memcached.1.host")) {            int nb = 1;            String addresses = "";            while (Play.configuration.containsKey("memcached." + nb + ".host")) {                addresses += Play.configuration.get("memcached." + nb + ".host") + " ";                nb++;            }            addrs = AddrUtil.getAddresses(addresses);        } else {            throw new ConfigurationException("Bad configuration for memcached: missing host(s)");        }        if (Play.configuration.containsKey("memcached.user")) {            String memcacheUser = Play.configuration.getProperty("memcached.user");            String memcachePassword = Play.configuration.getProperty("memcached.password");            if (memcachePassword == null) {                throw new ConfigurationException("Bad configuration for memcached: missing password");            }            // Use plain SASL to connect to memcached            AuthDescriptor ad = new AuthDescriptor(new String[]{"PLAIN"},                                    new PlainCallbackHandler(memcacheUser, memcachePassword));            ConnectionFactory cf = new ConnectionFactoryBuilder()                                        .setProtocol(ConnectionFactoryBuilder.Protocol.BINARY)                                        .setAuthDescriptor(ad)                                        .build();            client = new MemcachedClient(cf, addrs);        } else {            client = new MemcachedClient(addrs);        }    }

• 基本的操作

public void add(String key, Object value, int expiration) {        client.add(key, expiration, value, tc);    }    public Object get(String key) {        Future<Object> future = client.asyncGet(key, tc);        try {            return future.get(1, TimeUnit.SECONDS);        } catch (Exception e) {            future.cancel(false);        }        return null;    }    public void clear() {        client.flush();    }    public void delete(String key) {        client.delete(key);    }    public Map<String, Object> get(String[] keys) {        Future<Map<String, Object>> future = client.asyncGetBulk(tc, keys);        try {            return future.get(1, TimeUnit.SECONDS);        } catch (Exception e) {            future.cancel(false);        }        return Collections.<String, Object>emptyMap();    }    public long incr(String key, int by) {        return client.incr(key, by, 0);    }    public long decr(String key, int by) {        return client.decr(key, by, 0);    }    public void replace(String key, Object value, int expiration) {        client.replace(key, expiration, value, tc);    }    public boolean safeAdd(String key, Object value, int expiration) {        Future<Boolean> future = client.add(key, expiration, value, tc);        try {            return future.get(1, TimeUnit.SECONDS);        } catch (Exception e) {            future.cancel(false);        }        return false;    }    public boolean safeDelete(String key) {        Future<Boolean> future = client.delete(key);        try {            return future.get(1, TimeUnit.SECONDS);        } catch (Exception e) {            future.cancel(false);        }        return false;    }