设计模式课程 设计模式精讲 11-3 装饰者模式源码解析

1　　　　源码解析

1.1　　源码解析1（jdk1.7中的应用一）

1.2　　源码解析2（jdk1.7中的应用二）

1.3　　源码解析3（Spring中的应用）

1.4　　源码解析4（Servlet中的应用）

1.5　　源码解析5（myBaties中的应用）

1　　　　源码解析

1.1　　源码解析1（jdk1.7中的应用一）

BufferedReader

/**
  *
  *  bufferedReader 继承了Reader，并把Reader组合到BufferedReader中
  */
public class BufferedReader extends Reader {

    private Reader in;

/**
     * Creates a buffering character-input stream that uses an input buffer of
     * the specified size.
     *
     * @param  in   A Reader
     * @param  sz   Input-buffer size
     *
     * @exception  IllegalArgumentException  If sz is <= 0
     */
    public BufferedReader(Reader in, int sz) {
        super(in);
        if (sz <= 0)
            throw new IllegalArgumentException("Buffer size <= 0");
        this.in = in;
        cb = new char[sz];
        nextChar = nChars = 0;
    }

}

Reader

/**
   *   Reader是抽象类    
   */ 
public abstract class Reader implements Readable, Closeable {

）

 

1.2　　源码解析2（jdk1.7中的应用二）

uml类图

装饰父类1的子类：BufferedInputStream

public
class BufferedInputStream extends FilterInputStream {

//传入父类的父类
    public BufferedInputStream(InputStream in) {
        this(in, defaultBufferSize);
    }

/**
   *    实现读取流数据，起到装饰的作用
   */
private void fill() throws IOException {
        byte[] buffer = getBufIfOpen();
        if (markpos < 0)
            pos = 0;            /* no mark: throw away the buffer */
        else if (pos >= buffer.length)  /* no room left in buffer */
            if (markpos > 0) {  /* can throw away early part of the buffer */
                int sz = pos - markpos;
                System.arraycopy(buffer, markpos, buffer, 0, sz);
                pos = sz;
                markpos = 0;
            } else if (buffer.length >= marklimit) {
                markpos = -1;   /* buffer got too big, invalidate mark */
                pos = 0;        /* drop buffer contents */
            } else {            /* grow buffer */
                int nsz = pos * 2;
                if (nsz > marklimit)
                    nsz = marklimit;
                byte nbuf[] = new byte[nsz];
                System.arraycopy(buffer, 0, nbuf, 0, pos);
                if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {
                    // Can't replace buf if there was an async close.
                    // Note: This would need to be changed if fill()
                    // is ever made accessible to multiple threads.
                    // But for now, the only way CAS can fail is via close.
                    // assert buf == null;
                    throw new IOException("Stream closed");
                }
                buffer = nbuf;
            }
        count = pos;
        int n = getInIfOpen().read(buffer, pos, buffer.length - pos);
        if (n > 0)
            count = n + pos;
    }

}

装饰父类1：FilterInputStream

public
class FilterInputStream extends InputStream {
    /**
     * The input stream to be filtered.
     */
    protected volatile InputStream in;

    protected FilterInputStream(InputStream in) {
        this.in = in;
    }

}

被装饰类：InputStream

public abstract class InputStream implements Closeable {

}

装饰父类2：FileInputStream

public class FileInputStream extends InputStream
{
/*
 *  传入file，装饰成inputstream
*/
public FileInputStream(File file) throws FileNotFoundException {
        String name = (file != null ? file.getPath() : null);
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkRead(name);
        }
        if (name == null) {
            throw new NullPointerException();
        }
        if (file.isInvalid()) {
            throw new FileNotFoundException("Invalid file path");
        }
        fd = new FileDescriptor();
        fd.incrementAndGetUseCount();
        this.path = name;
        open(name);
    }

}

1.3　　源码解析3（Spring中的应用）

TransactionAwareCacheDecorator

/**
   *    该类是储存缓存和事务的相关类
   */
public class TransactionAwareCacheDecorator implements Cache {
    private final Cache targetCache;

    public TransactionAwareCacheDecorator(Cache targetCache) {
        Assert.notNull(targetCache, "Target Cache must not be null");
        this.targetCache = targetCache;
    }
}

1.4　　源码解析4（Servlet中的应用）

1.5　　源码解析5（myBaties中的应用）

public class FifoCache implements Cache {

  private final Cache delegate;
  private Deque<Object> keyList;
  private int size;


  public FifoCache(Cache delegate) {
    this.delegate = delegate;
    this.keyList = new LinkedList<Object>();
    this.size = 1024;
  }
}