Java中InputStream转Byte Array或ByteBuffer呢?

InputStream转换为字节数组或字节buffer的实现思路
      方式1:原始方式
      
     方式2:使用Guava框架

    方式3:Commons IO框架

@Test
public void givenUsingPlainJava_whenConvertingAnInputStreamToAByteArray_thenCorrect() 
  throws IOException {
    InputStream initialStream = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
 
    byte[] targetArray = new byte[initialStream.available()];
    initialStream.read(targetArray);
}

@Test
public void
  givenUsingPlainJavaOnUnknownSizeStream_whenConvertingAnInputStreamToAByteArray_thenCorrect() 
  throws IOException {
    InputStream is = new ByteArrayInputStream(new byte[] { 0, 1, 2 }); // not really unknown
 
    ByteArrayOutputStream buffer = new ByteArrayOutputStream();
    int nRead;
    byte[] data = new byte[1024];
    while ((nRead = is.read(data, 0, data.length)) != -1) {
        buffer.write(data, 0, nRead);
    }
 
    buffer.flush();
    byte[] byteArray = buffer.toByteArray();
}

使用Guava实现

@Test
public void givenUsingGuava_whenConvertingAnInputStreamToAByteArray_thenCorrect() 
  throws IOException {
    InputStream initialStream = ByteSource.wrap(new byte[] { 0, 1, 2 }).openStream();
     
    byte[] targetArray = ByteStreams.toByteArray(initialStream);
}

使用Commons IO

@Test
public void givenUsingCommonsIO_whenConvertingAnInputStreamToAByteArray_thenCorrect() 
  throws IOException {
    ByteArrayInputStream initialStream = new ByteArrayInputStream(new byte[] { 0, 1, 2 });
     
    byte[] targetArray = IOUtils.toByteArray(initialStream);
}
 
IOUtils.toByteArray() 方法内部缓存输入流，因此不再需要使用BufferedInputStream实例。

转成ByteBuffer

@Test
public void givenUsingCoreClasses_whenByteArrayInputStreamToAByteBuffer_thenLengthMustMatch() 
  throws IOException {
    byte[] input = new byte[] { 0, 1, 2 };
    InputStream initialStream = new ByteArrayInputStream(input);
    ByteBuffer byteBuffer = ByteBuffer.allocate(3);
    while (initialStream.available() > 0) {
        byteBuffer.put((byte) initialStream.read());
    }
 
    assertEquals(byteBuffer.position(), input.length);
}

使用Guava实现

@Test
public void givenUsingGuava__whenByteArrayInputStreamToAByteBuffer_thenLengthMustMatch() 
  throws IOException {
    InputStream initialStream = ByteSource
      .wrap(new byte[] { 0, 1, 2 })
      .openStream();
    byte[] targetArray = ByteStreams.toByteArray(initialStream);
    ByteBuffer bufferByte = ByteBuffer.wrap(targetArray);
    while (bufferByte.hasRemaining()) {
        bufferByte.get();
    }
 
    assertEquals(bufferByte.position(), targetArray.length);
}

使用Commons IO转换byteBuffer

@Test
public void givenUsingCommonsIo_whenByteArrayInputStreamToAByteBuffer_thenLengthMustMatch() 
  throws IOException {
    byte[] input = new byte[] { 0, 1, 2 };
    InputStream initialStream = new ByteArrayInputStream(input);
    ByteBuffer byteBuffer = ByteBuffer.allocate(3);
    ReadableByteChannel channel = newChannel(initialStream);
    IOUtils.readFully(channel, byteBuffer);
 
    assertEquals(byteBuffer.position(), input.length);
}