android实现缓存图片等数据

package cc.util.cache; import java.io.Serializable;import java.util.Objects; /**  封装网络数据， 将数据的Etag、lastModified获取到， 下次请求的时候提取出来到服务器比对 * Help to wrap byte data which obtains from network, It will work with {@link cc.util.cache.NetChacheManager}  * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun 2014 */public class NetByteWrapper implements Serializable {   private final static long serialVersionUID = 1L;   /** data from network */  private byte[] data;  /** data size */  int contentLength;  /** latested modify time */  private long lastModified;  /** ETag： look up HTTP Protocol */  private String ETag;   public NetByteWrapper(byte[] data, long lastModified, String Etag) {    this.data = data;    this.lastModified = lastModified;    this.ETag = Etag;  }     public byte[] getData() {    return data;  }  public void setData(byte[] data) {    this.data = data;  }   public long getLastModified() {    return lastModified;  }  public void setLastModified(long lastModified) {    this.lastModified = lastModified;  }   public String getETag() {    return ETag;  }     public void setETag(String eTag) {    this.ETag = eTag;  }     public int getContentLength() {    return Objects.isNull(data) ? 0 : data.length;  }}  package cc.util.cache; import java.lang.ref.ReferenceQueue;import java.lang.ref.SoftReference; /**采用软引用方式将数据存放起来 * enclose {@link cc.util.cache.NetByteWrapper} with {@link java.lang.ref.SoftReference}, In order to recycle the memory * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun. 2014 */public class NetByteSoftReference extends SoftReference<NetByteWrapper> {     private String key = "";  private long length = 0;   public NetByteSoftReference(String key, NetByteWrapper arg0) {    this(key, arg0, null);  }   public NetByteSoftReference(String key, NetByteWrapper arg0,      ReferenceQueue<? super NetByteWrapper> arg1) {    super(arg0, arg1);    // TODO Auto-generated constructor stub    this.key = key;    this.length = arg0.getContentLength();  }     public String getKey() {    return key;  }     public long getLength() {    return length;  } }  package cc.util.cache; import java.lang.ref.ReferenceQueue;import java.lang.ref.SoftReference;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.util.Iterator;import java.util.LinkedHashMap;import java.util.Objects; /** * 采用LinkedHashMap自带的LRU 算法缓存数据， 可检测对象是否已被虚拟机回收，并且重新计算当前缓存大小，清除缓存中无用的键值对象(即已经被虚拟机回收但未从缓存清除的数据)； * 默认内存缓存大小为: 4 * 1024 * 1024 可通过通过setMaxCacheSize重新设置缓存大小，可手动清空内存缓存，支持采用内存映射方式读取缓存 * <br>支持内存缓存和磁盘缓存方式， 通过 {@link cc.util.cache.NetByteWrapper} 支持HTTP缓存 （注：详细参考cc.util.http包） * @author wangcccong * @version 1.1406 * <br> create at: Tues, 10 Jun 2014 */public class NetCacheManager {   /** max cache size */  private long MAX_CACHE_SIZE = 4 * 1024 * 1024;  private long cacheSize = 0;    private static NetCacheManager instance = null;     private final ReferenceQueue<NetByteWrapper> referenceQueue;  private final LinkedHashMap<String, NetByteSoftReference> cacheMap;     private NetCacheManager(){    referenceQueue = new ReferenceQueue<NetByteWrapper>();    cacheMap = new LinkedHashMap<String, NetByteSoftReference>(16, 0.75f, true) {       private static final long serialVersionUID = -8378285623387632829L;      @Override      protected boolean removeEldestEntry(          java.util.Map.Entry<String, NetByteSoftReference> eldest) {        // TODO Auto-generated method stub        boolean shouldRemove = cacheSize > MAX_CACHE_SIZE;        if (shouldRemove) {          cacheSize -= eldest.getValue().getLength();          System.gc();        }        return shouldRemove;      }    };  }     /** singleton model */  public static synchronized NetCacheManager newInstance(){    if (Objects.isNull(instance)) {      instance = new NetCacheManager();    }    return instance;  }     /**   * reset the memory cache size   * @param cacheSize   */  public void setMaxCacheSize(long cacheSize) {    this.MAX_CACHE_SIZE = cacheSize;  }     /**   * 获取当前内存缓存大小   * @return   */  public long getCacheSize() {    return cacheSize;  }     /**   * 将数据缓存至内存， 如果http返回的数据<b>不支持</b>缓存则采用此方法，缓存的key一般为请求的url   * @param key   * @param value   */  public void cacheInMemory(String key, byte[] value) {    this.cacheInMemory(key, value, 0, null);  }     /**   * 将数据缓存至内存， 如果http返回的数据<b>支持</b>缓存则采用此方法   * @param key   * @param value   * @param lastModified   */  public void cacheInMemory(String key, byte[] value, long lastModified) {    this.cacheInMemory(key, value, lastModified, null);  }     /**   * 将数据缓存至内存， 如果http返回的数据<b>支持</b>缓存则采用此方法   * @param key   * @param value   * @param Etags   */  public void cacheInMemory(String key, byte[] value, String Etags) {    this.cacheInMemory(key, value, 0, Etags);  }     /**   * 将数据缓存至内存， 如果http返回的数据<b>支持</b>缓存则采用此方法   * @param key   * @param value   * @param lastModified   * @param Etags   */  private void cacheInMemory(String key, byte[] value, long lastModified, String Etags) {    Objects.requireNonNull(key, "key must not be null");    clearRecycledObject();    NetByteWrapper wrapper = new NetByteWrapper(value, lastModified, Etags);    NetByteSoftReference byteRef = new NetByteSoftReference(key, wrapper, referenceQueue);    cacheMap.put(key, byteRef);    value = null;    wrapper = null;  }     /**   * 缓存至磁盘, 默认不首先缓存到内存   * @param key   * @param value   * @param path   */  public void cacheInDisk(String key, byte[] value, String path) {    cacheInDisk(key, value, path, false);  }     /**   *    * @param key   * @param value   * @param path   * @param cacheInMemory   */  public void cacheInDisk(String key, byte[] value, String path, boolean cacheInMemory) {    this.cacheInDisk(key, value, 0, null, path, cacheInMemory);  }     /**   *    * @param key   * @param value   * @param lastModified   * @param Etags   * @param path   * @param cacheInMemory   */  private void cacheInDisk(String key, byte[] value, long lastModified, String Etags, String path, boolean cacheInMemory) {    if (cacheInMemory) cacheInMemory(key, value, lastModified, Etags);    try (FileOutputStream fos = new FileOutputStream(path);        ObjectOutputStream oos = new ObjectOutputStream(fos)) {        NetByteWrapper wrapper = new NetByteWrapper(value, lastModified, Etags);        oos.writeObject(wrapper);    } catch (Exception e) {        // TODO: handle exception      e.printStackTrace();    }  }     /**   * get {@link cc.util.cache.NetByteWrapper} from memory according to key   * @param key   * @return {@link cc.util.cache.NetByteWrapper}   */  public NetByteWrapper getFromMemory(String key) {    SoftReference<NetByteWrapper> softReference = cacheMap.get(key);    return Objects.nonNull(softReference) ? softReference.get() : null;  }     /**   * get byte[] from memory according to key   * @param context   * @param key   * @return   */  public byte[] getByteFromMemory(String key) {    NetByteWrapper wrapper = getFromMemory(key);    return Objects.nonNull(wrapper) ? wrapper.getData() : null;  }     /**   * 从磁盘获取数据   * @param path   * @return {@link cc.util.cache.NetByteWrapper}   */  public NetByteWrapper getFromDisk(String path) {    try (FileInputStream fis = new FileInputStream(path);        ObjectInputStream ois = new ObjectInputStream(fis)) {      NetByteWrapper wrapper = (NetByteWrapper) ois.readObject();      return wrapper;    } catch (Exception e) {      // TODO: handle exception      e.printStackTrace();      return null;    }  }     /**   * 采用内存映射的方式从磁盘获取数据（加快读取缓存的大文件）   * @param path   * @return   */  public NetByteWrapper getFromDiskByMapped(String path) {    try (FileInputStream fis = new FileInputStream(path);        FileChannel channel= fis.getChannel();        ByteArrayOutputStream baos = new ByteArrayOutputStream()){      MappedByteBuffer mbb = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());      byte[] bts = new byte[1024];       int len = (int) channel.size();      for (int offset = 0; offset < len; offset += 1024) {         if (len - offset > 1024) mbb.get(bts);        else mbb.get((bts = new byte[len - offset]));         baos.write(bts);      }       ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());      ObjectInputStream ois = new ObjectInputStream(bais);      NetByteWrapper wrapper = (NetByteWrapper) ois.readObject();      bais.close();      ois.close();      return wrapper;    } catch (Exception e) {      // TODO: handle exception      e.printStackTrace();      return null;    }  }     /**   * 从磁盘获取缓存的byte[] 数据   * @param path   * @return   */  public byte[] getByteFromDisk(String path) {    NetByteWrapper wrapper = getFromDisk(path);    return Objects.isNull(wrapper) ? null : wrapper.getData();  }     /**   * 通过内存映射放射从磁盘获取缓存的byte[] 数据   * @param path   * @return   */  public byte[] getByteFromDiskByMapped(String path) {    NetByteWrapper wrapper = getFromDiskByMapped(path);    return Objects.isNull(wrapper) ? null : wrapper.getData();  }     /**   * calculate the size of the cache memory   */  private void clearRecycledObject() {    NetByteSoftReference ref = null;    //检测对象是否被回收，如果被回收则从缓存中移除死项    while (Objects.nonNull((ref = (NetByteSoftReference) referenceQueue.poll()))) {      cacheMap.remove(ref.getKey());    }    cacheSize = 0;    Iterator<String> keys = cacheMap.keySet().iterator();    while (keys.hasNext()) {      cacheSize += cacheMap.get(keys.next()).getLength();    }  }     /**   * clear the memory cache   */  public void clearCache() {    clearRecycledObject();    cacheMap.clear();    System.gc();    System.runFinalization();  }   }