如何将整个读InputStream
入字节数组?
33 回答
您可以使用 Apache Commons IO来处理这个和类似的任务。
该IOUtils
类型有一个静态方法来读取一个InputStream
并返回一个byte[]
。
InputStream is;
byte[] bytes = IOUtils.toByteArray(is);
这在内部创建 aByteArrayOutputStream
并将字节复制到输出,然后调用toByteArray()
. 它通过复制 4KiB 块中的字节来处理大文件。
您需要从中读取每个字节InputStream
并将其写入ByteArrayOutputStream
.
然后,您可以通过调用来检索底层字节数组toByteArray()
:
InputStream is = ...
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[16384];
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
return buffer.toByteArray();
最后,在 20 年后,有了一个简单的解决方案,无需 3rd 方库,这要归功于Java 9:
InputStream is;
…
byte[] array = is.readAllBytes();
还要注意便利方法readNBytes(byte[] b, int off, int len)
和transferTo(OutputStream)
解决重复性需求。
使用 vanilla JavaDataInputStream
及其readFully
方法(至少从 Java 1.4 开始存在):
...
byte[] bytes = new byte[(int) file.length()];
DataInputStream dis = new DataInputStream(new FileInputStream(file));
dis.readFully(bytes);
...
这种方法还有其他一些风格,但我一直在这个用例中使用它。
如果您碰巧使用Google Guava,它就像使用一样简单ByteStreams
:
byte[] bytes = ByteStreams.toByteArray(inputStream);
与往常一样,Spring 框架(自 3.2.2 以来的 spring-core)也为您提供了一些东西:StreamUtils.copyToByteArray()
安全解决方案(正确关闭流):
Java 9+:
final byte[] bytes; try (inputStream) { bytes = inputStream.readAllBytes(); }
爪哇 8:
public static byte[] readAllBytes(InputStream inputStream) throws IOException { final int bufLen = 4 * 0x400; // 4KB byte[] buf = new byte[bufLen]; int readLen; IOException exception = null; try { try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) { while ((readLen = inputStream.read(buf, 0, bufLen)) != -1) outputStream.write(buf, 0, readLen); return outputStream.toByteArray(); } } catch (IOException e) { exception = e; throw e; } finally { if (exception == null) inputStream.close(); else try { inputStream.close(); } catch (IOException e) { exception.addSuppressed(e); } } }
Kotlin(当 Java 9+ 不可访问时):
@Throws(IOException::class) fun InputStream.readAllBytes(): ByteArray { val bufLen = 4 * 0x400 // 4KB val buf = ByteArray(bufLen) var readLen: Int = 0 ByteArrayOutputStream().use { o -> this.use { i -> while (i.read(buf, 0, bufLen).also { readLen = it } != -1) o.write(buf, 0, readLen) } return o.toByteArray() } }
避免嵌套
use
见这里。
Scala(当 Java 9+ 无法访问时)(作者: @Joan . Thx):
def readAllBytes(inputStream: InputStream): Array[Byte] = Stream.continually(inputStream.read).takeWhile(_ != -1).map(_.toByte).toArray
public static byte[] getBytesFromInputStream(InputStream is) throws IOException {
ByteArrayOutputStream os = new ByteArrayOutputStream();
byte[] buffer = new byte[0xFFFF];
for (int len = is.read(buffer); len != -1; len = is.read(buffer)) {
os.write(buffer, 0, len);
}
return os.toByteArray();
}
万一有人仍在寻找没有依赖关系的解决方案,并且如果您有文件.
数据输入流
byte[] data = new byte[(int) file.length()];
DataInputStream dis = new DataInputStream(new FileInputStream(file));
dis.readFully(data);
dis.close();
字节数组输出流
InputStream is = new FileInputStream(file);
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[(int) file.length()];
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
随机存取文件
RandomAccessFile raf = new RandomAccessFile(file, "r");
byte[] data = new byte[(int) raf.length()];
raf.readFully(data);
你真的需要图像byte[]
吗?您到底期望什么byte[]
- 图像文件的完整内容,以图像文件的任何格式编码,或 RGB 像素值?
此处的其他答案向您展示了如何将文件读入byte[]
. 您byte[]
将包含文件的确切内容,您需要对其进行解码才能对图像数据执行任何操作。
Java 用于读取(和写入)图像的标准 API 是 ImageIO API,您可以在 package 中找到它javax.imageio
。您只需一行代码即可从文件中读取图像:
BufferedImage image = ImageIO.read(new File("image.jpg"));
这会给你一个BufferedImage
,而不是一个byte[]
。要获取图像数据,您可以调用getRaster()
. BufferedImage
这将为您提供一个Raster
对象,该对象具有访问像素数据的方法(它有几个getPixel()
/getPixels()
方法)。
查找 、 等的javax.imageio.ImageIO
APIjava.awt.image.BufferedImage
文档java.awt.image.Raster
。
ImageIO 默认支持多种图像格式:JPEG、PNG、BMP、WBMP 和 GIF。可以添加对更多格式的支持(您需要一个实现 ImageIO 服务提供者接口的插件)。
另请参阅以下教程:使用图像
如果您不想使用 Apache commons-io 库,则此代码段取自 sun.misc.IOUtils 类。它几乎是使用 ByteBuffers 的常见实现的两倍:
public static byte[] readFully(InputStream is, int length, boolean readAll)
throws IOException {
byte[] output = {};
if (length == -1) length = Integer.MAX_VALUE;
int pos = 0;
while (pos < length) {
int bytesToRead;
if (pos >= output.length) { // Only expand when there's no room
bytesToRead = Math.min(length - pos, output.length + 1024);
if (output.length < pos + bytesToRead) {
output = Arrays.copyOf(output, pos + bytesToRead);
}
} else {
bytesToRead = output.length - pos;
}
int cc = is.read(output, pos, bytesToRead);
if (cc < 0) {
if (readAll && length != Integer.MAX_VALUE) {
throw new EOFException("Detect premature EOF");
} else {
if (output.length != pos) {
output = Arrays.copyOf(output, pos);
}
break;
}
}
pos += cc;
}
return output;
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
while (true) {
int r = in.read(buffer);
if (r == -1) break;
out.write(buffer, 0, r);
}
byte[] ret = out.toByteArray();
Input Stream is ...
ByteArrayOutputStream bos = new ByteArrayOutputStream();
int next = in.read();
while (next > -1) {
bos.write(next);
next = in.read();
}
bos.flush();
byte[] result = bos.toByteArray();
bos.close();
@Adamski:您可以完全避免缓冲。
从http://www.exampledepot.com/egs/java.io/File2ByteArray.html复制的代码(是的,它非常冗长,但需要一半的内存大小作为其他解决方案。)
// Returns the contents of the file in a byte array.
public static byte[] getBytesFromFile(File file) throws IOException {
InputStream is = new FileInputStream(file);
// Get the size of the file
long length = file.length();
// You cannot create an array using a long type.
// It needs to be an int type.
// Before converting to an int type, check
// to ensure that file is not larger than Integer.MAX_VALUE.
if (length > Integer.MAX_VALUE) {
// File is too large
}
// Create the byte array to hold the data
byte[] bytes = new byte[(int)length];
// Read in the bytes
int offset = 0;
int numRead = 0;
while (offset < bytes.length
&& (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
offset += numRead;
}
// Ensure all the bytes have been read in
if (offset < bytes.length) {
throw new IOException("Could not completely read file "+file.getName());
}
// Close the input stream and return bytes
is.close();
return bytes;
}
Java 9 最终会给你一个不错的方法:
InputStream in = ...;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
in.transferTo( bos );
byte[] bytes = bos.toByteArray();
我知道为时已晚,但我认为这是更清晰的解决方案,更具可读性......
/**
* method converts {@link InputStream} Object into byte[] array.
*
* @param stream the {@link InputStream} Object.
* @return the byte[] array representation of received {@link InputStream} Object.
* @throws IOException if an error occurs.
*/
public static byte[] streamToByteArray(InputStream stream) throws IOException {
byte[] buffer = new byte[1024];
ByteArrayOutputStream os = new ByteArrayOutputStream();
int line = 0;
// read bytes from stream, and store them in buffer
while ((line = stream.read(buffer)) != -1) {
// Writes bytes from byte array (buffer) into output stream.
os.write(buffer, 0, line);
}
stream.close();
os.flush();
os.close();
return os.toByteArray();
}
在将 S3 对象转换为 ByteArray 时,我们看到一些 AWS 事务出现延迟。
注意:S3 对象是 PDF 文档(最大大小为 3 mb)。
我们使用选项 #1 (org.apache.commons.io.IOUtils) 将 S3 对象转换为 ByteArray。我们注意到 S3 提供了内置 IOUtils 方法来将 S3 对象转换为 ByteArray,我们要求您确认将 S3 对象转换为 ByteArray 的最佳方法是什么以避免延迟。
选项1:
import org.apache.commons.io.IOUtils;
is = s3object.getObjectContent();
content =IOUtils.toByteArray(is);
选项#2:
import com.amazonaws.util.IOUtils;
is = s3object.getObjectContent();
content =IOUtils.toByteArray(is);
如果我们有任何其他更好的方法将 s3 对象转换为字节数组,请告诉我
我试图通过编写垃圾数据的修复程序来编辑@numan 的答案,但编辑被拒绝。虽然这段简短的代码并不出色,但我看不到任何其他更好的答案。这对我来说最有意义:
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024]; // you can configure the buffer size
int length;
while ((length = in.read(buffer)) != -1) out.write(buffer, 0, length); //copy streams
in.close(); // call this in a finally block
byte[] result = out.toByteArray();
btw ByteArrayOutputStream 不需要关闭。为便于阅读,省略了 try/finally 结构
请参阅InputStream.available()
文档:
尤其重要的是要意识到您不能使用此方法来调整容器的大小,并假设您可以读取整个流而不需要调整容器的大小。这样的调用者可能应该将他们读取的所有内容写入 ByteArrayOutputStream 并将其转换为字节数组。或者,如果您正在从文件中读取, File.length 返回文件的当前长度(尽管假设文件的长度不能改变可能是不正确的,读取文件本质上是活泼的)。
如果由于某种原因不在表格中,则将其包装在 DataInputStream 中,只需使用 read 对其进行锤击,直到它为您提供 -1 或您要求的整个块。
public int readFully(InputStream in, byte[] data) throws IOException {
int offset = 0;
int bytesRead;
boolean read = false;
while ((bytesRead = in.read(data, offset, data.length - offset)) != -1) {
read = true;
offset += bytesRead;
if (offset >= data.length) {
break;
}
}
return (read) ? offset : -1;
}
Java 8 方式(感谢BufferedReader和Adam Bien)
private static byte[] readFully(InputStream input) throws IOException {
try (BufferedReader buffer = new BufferedReader(new InputStreamReader(input))) {
return buffer.lines().collect(Collectors.joining("\n")).getBytes(<charset_can_be_specified>);
}
}
请注意,此解决方案会擦除回车符('\r') 并且可能不合适。
这是一个优化版本,它尽量避免复制数据字节:
private static byte[] loadStream (InputStream stream) throws IOException {
int available = stream.available();
int expectedSize = available > 0 ? available : -1;
return loadStream(stream, expectedSize);
}
private static byte[] loadStream (InputStream stream, int expectedSize) throws IOException {
int basicBufferSize = 0x4000;
int initialBufferSize = (expectedSize >= 0) ? expectedSize : basicBufferSize;
byte[] buf = new byte[initialBufferSize];
int pos = 0;
while (true) {
if (pos == buf.length) {
int readAhead = -1;
if (pos == expectedSize) {
readAhead = stream.read(); // test whether EOF is at expectedSize
if (readAhead == -1) {
return buf;
}
}
int newBufferSize = Math.max(2 * buf.length, basicBufferSize);
buf = Arrays.copyOf(buf, newBufferSize);
if (readAhead != -1) {
buf[pos++] = (byte)readAhead;
}
}
int len = stream.read(buf, pos, buf.length - pos);
if (len < 0) {
return Arrays.copyOf(buf, pos);
}
pos += len;
}
}
另一种情况是在向服务器发送请求并等待响应后,通过流获取正确的字节数组。
/**
* Begin setup TCP connection to PC app
* to open integrate connection between mobile app and pc app (or mobile app)
*/
mSocket = new Socket(IP, port);
// mSocket.setSoTimeout(30000);
DataOutputStream mDos = new DataOutputStream(mSocket.getOutputStream());
String str = "MobileRequest#" + params[0] + "#<EOF>";
mDos.write(str.getBytes());
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
/* Since data are accepted as byte, all of them will be collected in the
following byte array which initialised with accepted data length. */
DataInputStream mDis = new DataInputStream(mSocket.getInputStream());
byte[] data = new byte[mDis.available()];
// Collecting data into byte array
for (int i = 0; i < data.length; i++)
data[i] = mDis.readByte();
// Converting collected data in byte array into String.
String RESPONSE = new String(data);
如果您使用 ByteArrayOutputStream,您正在做一个额外的副本。如果你在开始读之前就知道了流的长度(比如InputStream实际上是一个FileInputStream,你可以在文件上调用file.length(),或者InputStream是一个zipfile入口InputStream,你可以调用zipEntry. length()),那么直接写入 byte[] 数组要好得多——它使用了一半的内存,并且节省了时间。
// Read the file contents into a byte[] array
byte[] buf = new byte[inputStreamLength];
int bytesRead = Math.max(0, inputStream.read(buf));
// If needed: for safety, truncate the array if the file may somehow get
// truncated during the read operation
byte[] contents = bytesRead == inputStreamLength ? buf
: Arrays.copyOf(buf, bytesRead);
注意,上面的最后一行处理在读取流时文件被截断,如果您需要处理这种可能性,但是如果在读取流时文件变长,则 byte[] 数组中的内容不会被延长要包含新文件内容,数组将被简单地截断为旧长度inputStreamLength。
我用这个。
public static byte[] toByteArray(InputStream is) throws IOException {
ByteArrayOutputStream output = new ByteArrayOutputStream();
try {
byte[] b = new byte[4096];
int n = 0;
while ((n = is.read(b)) != -1) {
output.write(b, 0, n);
}
return output.toByteArray();
} finally {
output.close();
}
}
这是我的复制粘贴版本:
@SuppressWarnings("empty-statement")
public static byte[] inputStreamToByte(InputStream is) throws IOException {
if (is == null) {
return null;
}
// Define a size if you have an idea of it.
ByteArrayOutputStream r = new ByteArrayOutputStream(2048);
byte[] read = new byte[512]; // Your buffer size.
for (int i; -1 != (i = is.read(read)); r.write(read, 0, i));
is.close();
return r.toByteArray();
}
Java 7 及更高版本:
import sun.misc.IOUtils;
...
InputStream in = ...;
byte[] buf = IOUtils.readFully(in, -1, false);
你可以试试Cactoos:
byte[] array = new BytesOf(stream).bytes();
Kotlin 中的解决方案(当然也可以在 Java 中使用),其中包括您是否知道大小的两种情况:
fun InputStream.readBytesWithSize(size: Long): ByteArray? {
return when {
size < 0L -> this.readBytes()
size == 0L -> ByteArray(0)
size > Int.MAX_VALUE -> null
else -> {
val sizeInt = size.toInt()
val result = ByteArray(sizeInt)
readBytesIntoByteArray(result, sizeInt)
result
}
}
}
fun InputStream.readBytesIntoByteArray(byteArray: ByteArray,bytesToRead:Int=byteArray.size) {
var offset = 0
while (true) {
val read = this.read(byteArray, offset, bytesToRead - offset)
if (read == -1)
break
offset += read
if (offset >= bytesToRead)
break
}
}
如果您知道大小,与其他解决方案相比,它可以节省两倍的内存使用量(在短时间内,但仍然可能有用)。那是因为您必须将整个流读取到最后,然后将其转换为字节数组(类似于 ArrayList 将其转换为数组)。
因此,例如,如果您使用的是 Android,并且需要处理一些 Uri,则可以尝试使用以下方法获取大小:
fun getStreamLengthFromUri(context: Context, uri: Uri): Long {
context.contentResolver.query(uri, arrayOf(MediaStore.MediaColumns.SIZE), null, null, null)?.use {
if (!it.moveToNext())
return@use
val fileSize = it.getLong(it.getColumnIndex(MediaStore.MediaColumns.SIZE))
if (fileSize > 0)
return fileSize
}
//if you wish, you can also get the file-path from the uri here, and then try to get its size, using this: https://stackoverflow.com/a/61835665/878126
FileUtilEx.getFilePathFromUri(context, uri, false)?.use {
val file = it.file
val fileSize = file.length()
if (fileSize > 0)
return fileSize
}
context.contentResolver.openInputStream(uri)?.use { inputStream ->
if (inputStream is FileInputStream)
return inputStream.channel.size()
else {
var bytesCount = 0L
while (true) {
val available = inputStream.available()
if (available == 0)
break
val skip = inputStream.skip(available.toLong())
if (skip < 0)
break
bytesCount += skip
}
if (bytesCount > 0L)
return bytesCount
}
}
return -1L
}
您可以使用cactoos库来提供可重用的面向对象的Java 组件。该库强调 OOP,因此没有静态方法、NULL 等,只有真实对象及其合约(接口)。像读取InputStream这样简单的操作,可以这样进行
final InputStream input = ...;
final Bytes bytes = new BytesOf(input);
final byte[] array = bytes.asBytes();
Assert.assertArrayEquals(
array,
new byte[]{65, 66, 67}
);
拥有Bytes
处理数据结构的专用类型byte[]
使我们能够使用 OOP 策略来解决手头的任务。程序“实用”方法将禁止我们做的事情。例如,您需要将从这里读取的字节编码InputStream
为 Base64。在这种情况下,您将使用装饰器模式并将 Bytes 对象包装在 Base64 的实现中。
cactoos已经提供了这样的实现:
final Bytes encoded = new BytesBase64(
new BytesOf(
new InputStreamOf("XYZ")
)
);
Assert.assertEquals(new TextOf(encoded).asString(), "WFla");
您可以使用装饰器模式以相同的方式对它们进行解码
final Bytes decoded = new Base64Bytes(
new BytesBase64(
new BytesOf(
new InputStreamOf("XYZ")
)
)
);
Assert.assertEquals(new TextOf(decoded).asString(), "XYZ");
无论您的任务是什么,您都可以创建自己的实现Bytes
来解决它。
/*InputStream class_InputStream = null;
I am reading class from DB
class_InputStream = rs.getBinaryStream(1);
Your Input stream could be from any source
*/
int thisLine;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
while ((thisLine = class_InputStream.read()) != -1) {
bos.write(thisLine);
}
bos.flush();
byte [] yourBytes = bos.toByteArray();
/*Don't forget in the finally block to close ByteArrayOutputStream & InputStream
In my case the IS is from resultset so just closing the rs will do it*/
if (bos != null){
bos.close();
}
这对我有用,
if(inputStream != null){
ByteArrayOutputStream contentStream = readSourceContent(inputStream);
String stringContent = contentStream.toString();
byte[] byteArr = encodeString(stringContent);
}
读取源内容()
public static ByteArrayOutputStream readSourceContent(InputStream inputStream) throws IOException {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
int nextChar;
try {
while ((nextChar = inputStream.read()) != -1) {
outputStream.write(nextChar);
}
outputStream.flush();
} catch (IOException e) {
throw new IOException("Exception occurred while reading content", e);
}
return outputStream;
}
编码字符串()
public static byte[] encodeString(String content) throws UnsupportedEncodingException {
byte[] bytes;
try {
bytes = content.getBytes();
} catch (UnsupportedEncodingException e) {
String msg = ENCODING + " is unsupported encoding type";
log.error(msg,e);
throw new UnsupportedEncodingException(msg, e);
}
return bytes;
}
下面的代码
public static byte[] serializeObj(Object obj) throws IOException {
ByteArrayOutputStream baOStream = new ByteArrayOutputStream();
ObjectOutputStream objOStream = new ObjectOutputStream(baOStream);
objOStream.writeObject(obj);
objOStream.flush();
objOStream.close();
return baOStream.toByteArray();
}
或者
BufferedImage img = ...
ByteArrayOutputStream baos = new ByteArrayOutputStream(1000);
ImageIO.write(img, "jpeg", baos);
baos.flush();
byte[] result = baos.toByteArray();
baos.close();