Class ByteArrayInputStream
A ByteArrayInputStream contains an internal buffer that contains bytes that may be read from the stream. An internal counter keeps track of the next byte to be supplied by the read method.
Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException .
Field Summary
Constructor Summary
Method Summary
Methods declared in class java.io.InputStream
Methods declared in class java.lang.Object
Field Details
buf
An array of bytes that was provided by the creator of the stream. Elements buf[0] through buf[count-1] are the only bytes that can ever be read from the stream; element buf[pos] is the next byte to be read.
pos
The index of the next character to read from the input stream buffer. This value should always be nonnegative and not larger than the value of count . The next byte to be read from the input stream buffer will be buf[pos] .
mark
The currently marked position in the stream. ByteArrayInputStream objects are marked at position zero by default when constructed. They may be marked at another position within the buffer by the mark() method. The current buffer position is set to this point by the reset() method. If no mark has been set, then the value of mark is the offset passed to the constructor (or 0 if the offset was not supplied).
count
The index one greater than the last valid character in the input stream buffer. This value should always be nonnegative and not larger than the length of buf . It is one greater than the position of the last byte within buf that can ever be read from the input stream buffer.
Constructor Details
ByteArrayInputStream
Creates a ByteArrayInputStream so that it uses buf as its buffer array. The buffer array is not copied. The initial value of pos is 0 and the initial value of count is the length of buf .
ByteArrayInputStream
Creates ByteArrayInputStream that uses buf as its buffer array. The initial value of pos is offset and the initial value of count is the minimum of offset+length and buf.length . The buffer array is not copied. The buffer’s mark is set to the specified offset.
Method Details
read
Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255 . If no byte is available because the end of the stream has been reached, the value -1 is returned. This read method cannot block.
read
Reads up to len bytes of data into an array of bytes from this input stream. If pos equals count , then -1 is returned to indicate end of file. Otherwise, the number k of bytes read is equal to the smaller of len and count-pos . If k is positive, then bytes buf[pos] through buf[pos+k-1] are copied into b[off] through b[off+k-1] in the manner performed by System.arraycopy . The value k is added into pos and k is returned. Unlike the overridden method of InputStream , this method returns -1 instead of zero if the end of the stream has been reached and len == 0 . This read method cannot block.
readAllBytes
Reads all remaining bytes from the input stream. This method blocks until all remaining bytes have been read and end of stream is detected, or an exception is thrown. This method does not close the input stream. When this stream reaches end of stream, further invocations of this method will return an empty byte array. Note that this method is intended for simple cases where it is convenient to read all bytes into a byte array. It is not intended for reading input streams with large amounts of data. The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified. If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes have been read. Consequently the input stream may not be at end of stream and may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
readNBytes
Reads the requested number of bytes from the input stream into the given byte array. This method blocks until len bytes of input data have been read, end of stream is detected, or an exception is thrown. The number of bytes actually read, possibly zero, is returned. This method does not close the input stream. In the case where end of stream is reached before len bytes have been read, then the actual number of bytes read will be returned. When this stream reaches end of stream, further invocations of this method will return zero. If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read up to len bytes. The first byte read is stored into element b[off] , the next one in to b[off+1] , and so on. The number of bytes read is, at most, equal to len . Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+ k -1] , leaving elements b[off+ k ] through b[off+len-1] unaffected. The behavior for the case where the input stream is asynchronously closed, or the thread interrupted during the read, is highly input stream specific, and therefore not specified. If an I/O error occurs reading from the input stream, then it may do so after some, but not all, bytes of b have been updated with data from the input stream. Consequently the input stream and b may be in an inconsistent state. It is strongly recommended that the stream be promptly closed if an I/O error occurs.
skip
Skips n bytes of input from this input stream. Fewer bytes might be skipped if the end of the input stream is reached. The actual number k of bytes to be skipped is equal to the smaller of n and count-pos . The value k is added into pos and k is returned.
available
Returns the number of remaining bytes that can be read (or skipped over) from this input stream. The value returned is count — pos , which is the number of bytes remaining to be read from the input buffer.
markSupported
Tests if this InputStream supports mark/reset. The markSupported method of ByteArrayInputStream always returns true .
mark
Set the current marked position in the stream. ByteArrayInputStream objects are marked at position zero by default when constructed. They may be marked at another position within the buffer by this method. If no mark has been set, then the value of the mark is the offset passed to the constructor (or 0 if the offset was not supplied). Note: The readAheadLimit for this class has no meaning.
reset
Resets the buffer to the marked position. The marked position is 0 unless another position was marked or an offset was specified in the constructor.
close
Closing a ByteArrayInputStream has no effect. The methods in this class can be called after the stream has been closed without generating an IOException .
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Convert Byte Array to InputStream in Java
In this article, we are going to learn how to convert byte array to InputStream in Java using built-in methods and external libraries like Guava and Apache Commons IO .
For more Java I/O related articles, check the following links:
2. Byte array to InputStream with ByteArrayInputStream
Let’s start with a simple solution that comes with plain Java:
package com.frontbackend.java.io.conversions.toinputstream.frombytearray; import java.io.ByteArrayInputStream; import java.io.InputStream; import java.nio.charset.StandardCharsets; public class ByteArrayToInputStreamUsingByteArrayInputStream < public static void main(String[] args) < byte[] bytes = "frontbackend.com".getBytes(StandardCharsets.UTF_8); InputStream targetStream = new ByteArrayInputStream(bytes); >> In this example we use ByteArrayInputStream object to create an instance of the InputStream type.
3. Convert byte array to InputStream using Guava
When using Guava library, first we have to wrap byte array with ByteSource object that contains openStream() method which returns InputStream :
package com.frontbackend.java.io.conversions.toinputstream.frombytearray; import java.io.IOException; import java.io.InputStream; import java.nio.charset.StandardCharsets; import com.google.common.io.ByteSource; public class ByteArrayToInputStreamUsingGuava < public static void main(String[] args) throws IOException < byte[] bytes = "frontbackend.com".getBytes(StandardCharsets.UTF_8); InputStream targetStream = ByteSource.wrap(bytes) .openStream(); >> 4. Using Apache Commons IO to convert byte [] to InputStream
Apache Commons IO library also gives us a solution but not so straightforward:
package com.frontbackend.java.io.conversions.toinputstream.frombytearray; import java.io.IOException; import java.io.InputStream; import java.nio.charset.StandardCharsets; import org.apache.commons.io.IOUtils; public class ByteArrayToInputStreamUsingIOUtils < public static void main(String[] args) throws IOException < byte[] bytes = "frontbackend.com".getBytes(StandardCharsets.UTF_8); InputStream inputStream = IOUtils.toInputStream(new String(bytes), StandardCharsets.UTF_8); >> First, we have to create a String object from our byte array, then use IOUtils.toInputStream to convert it into InputStream . Note that converting from String to InputStream requires encoding.
5. Conclusion
In this short article, we showed ways to convert byte array to InputStream in Java. We presented several solutions but suggest using the simplest one with the plain Java. This one is a straightforward way to achieve that conversion.
Code examples used in this tutorial can be found under our GitHub repository.
Byte[] to InputStream or OutputStream
I have a blob column in my database table, for which I have to use byte[] in my Java program as a mapping and to use this data I have to convert it to InputStream or OutputStream . But I don’t know what happens internally when I do so. Can anyone briefly explain me what’s happening when I do this conversion?
Shouldn’t the title be «array of bytes . » or «byte array. » or «byte[]. » instaed of «byte of array. «?
8 Answers 8
You create and use byte array I/O streams as follows:
byte[] source = . ; ByteArrayInputStream bis = new ByteArrayInputStream(source); // read bytes from bis . ByteArrayOutputStream bos = new ByteArrayOutputStream(); // write bytes to bos . byte[] sink = bos.toByteArray(); Assuming that you are using a JDBC driver that implements the standard JDBC Blob interface (not all do), you can also connect a InputStream or OutputStream to a blob using the getBinaryStream and setBinaryStream methods 1 , and you can also get and set the bytes directly.
(In general, you should take appropriate steps to handle any exceptions, and close streams. However, closing bis and bos in the example above is unnecessary, since they aren’t associated with any external resources; e.g. file descriptors, sockets, database connections.)
1 — The setBinaryStream method is really a getter. Go figure.
I’m assuming you mean that ‘use’ means read, but what i’ll explain for the read case can be basically reversed for the write case.
so you end up with a byte[]. this could represent any kind of data which may need special types of conversions (character, encrypted, etc). let’s pretend you want to write this data as is to a file.
firstly you could create a ByteArrayInputStream which is basically a mechanism to supply the bytes to something in sequence.
then you could create a FileOutputStream for the file you want to create. there are many types of InputStreams and OutputStreams for different data sources and destinations.
lastly you would write the InputStream to the OutputStream. in this case, the array of bytes would be sent in sequence to the FileOutputStream for writing. For this i recommend using IOUtils
byte[] bytes = . ;// ByteArrayInputStream in = new ByteArrayInputStream(bytes); FileOutputStream out = new FileOutputStream(new File(. )); IOUtils.copy(in, out); IOUtils.closeQuietly(in); IOUtils.closeQuietly(out); FileInputStream in = new FileInputStream(new File(. )); ByteArrayOutputStream out = new ByteArrayOutputStream(); IOUtils.copy(in, out); IOUtils.closeQuietly(in); IOUtils.closeQuietly(out); byte[] bytes = out.toByteArray(); if you use the above code snippets you’ll need to handle exceptions and i recommend you do the ‘closes’ in a finally block.