将InputStream转换为byte []的最有效方法？

Z时代
2024-01-10
分类：问答

ChannelBufferInputStream responseStream = (ChannelBufferInputStream) response.getBodyAsStream(); 
ArrayList<Byte> arrayList = new ArrayList<Byte>(); 
try { 
    while (responseStream.available() > 0) { 
     arrayList.add(responseStream.readByte()); 
    } 
} catch (IOException e) { 
    e.printStackTrace(); 
    return internalServerError(); 
} 
Iterator<Byte> iterator = arrayList.iterator(); 
byte[] bytes = new byte[arrayList.size()]; 
int i = 0; 
while (iterator.hasNext()) { 
    bytes[i++] = iterator.next(); 
}

我的网页应用程序的每一页加载都会调用此代码。它似乎运行得非常快，但有什么可以让这个运行速度更快吗？编辑将InputStream转换为byte []的最有效方法？

- 使用字节数组输出流

ChannelBufferInputStream responseStream = (ChannelBufferInputStream) response.getBodyAsStream(); 
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); 
try { 
    int read = responseStream.read(); 
    while (read != -1) { 
     byteArrayOutputStream.write(read); 
     read = responseStream.read(); 
    } 
} catch (IOException e) { 
    e.printStackTrace(); 
    return internalServerError(); 
} 
byte[] bytes = byteArrayOutputStream.toByteArray(); 
return ok(bytes).as(response.getHeader("Content-type"));

编辑更新时间 - 基准测试代码

平均时间后

ChannelBufferInputStream responseStream = (ChannelBufferInputStream) response.getBodyAsStream(); 
long t1 = System.nanoTime(); 
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); 
try { 
    int read = responseStream.read(); 
    while (read != -1) { 
     byteArrayOutputStream.write(read); 
     read = responseStream.read(); 
    } 
} catch (IOException e) { 
    e.printStackTrace(); 
    return internalServerError(); 
} 
byte[] bytes = byteArrayOutputStream.toByteArray(); 
long t2 = System.nanoTime(); 
System.out.println(t2-t1); 
return ok(bytes).as(response.getHeader("Content-type"));

100+请求 - 46873

平均时间100之后

ChannelBufferInputStream responseStream = (ChannelBufferInputStream) response.getBodyAsStream(); 
long t1 = System.nanoTime(); 
ArrayList<Byte> arrayList = new ArrayList<Byte>(); 
try { 
    while (responseStream.available() > 0) { 
     arrayList.add(responseStream.readByte()); 
    } 
} catch (IOException e) { 
    e.printStackTrace(); 
    return internalServerError(); 
} 
Iterator<Byte> iterator = arrayList.iterator(); 
byte[] bytes = new byte[arrayList.size()]; 
int i = 0; 
while (iterator.hasNext()) { 
    bytes[i++] = iterator.next(); 
} 
long t2 = System.nanoTime(); 
System.out.println(t2-t1); 
return ok(bytes).as(response.getHeader("Content-type"));

+请求 - 522848

平均时间后

long t1 = System.nanoTime(); 
byte[] bytes; 
try { 
    bytes = org.apache.commons.io.IOUtils.toByteArray(responseStream); 
} catch (Exception e) { 
    return internalServerError(); 
} 
long t2 = System.nanoTime(); 
System.out.println(t2-t1);

100+请求 - 45088的平均时间之后100+请求

long t1 = System.nanoTime(); 
byte[] bytes; 
try { 
    bytes = sun.misc.IOUtils.readFully(responseStream, -1, true); 
} catch (Exception e) { 
    return internalServerError(); 
} 
long t2 = System.nanoTime(); 
System.out.println(t2 - t1);

- 20180

回答：

是。使用ByteArrayOutputStream而不是ArrayList。然后从InputStream中读取大块字节（不使用available()，几乎总是从不使用），并将这些块写入ByteArrayOutputStream，直到read()方法返回-1。然后在您的ByteArrayOutputStream上调用toByteArray（）。

您可以使用Guava的ByteStreams.toByteArray()方法，它可以完成所有这些工作，或者您可以阅读其源代码以更好地了解它是如何工作的。阅读IO tutorial也可能有所帮助。