We Keep Coding

Base64 binary data type in java

I need to attach a Base64 binary element to a SOAP message...Im doing a dry run to check if I can convert a value read from a file into Base64 binary..
Here is the below code..In the last line I try to print the type of encoded1(I assume it should be Base64 binary values) but I get the following display..."Attachment[B"...How can I confirm if its Base64 binary string?
Path path = Paths.get("c:/tomcatupload/text.csv");
byte[] attachment1 = Files.readAllBytes(path);
byte[] encoded1 = Base64.encode(attachment1);
System.out.println("Attachment"+ encoded1.getClass().getName());

Base-64 encoding is a way to convert arbitrary bytes to bytes that fit in a range of text characters in ASCII encoding. This is done without any interpretation whatsoever - raw bytes are converted to base-64 on sender's end; the receiver converts them back to a stream of bytes, and that's all there is to it.
When your code prints encoded1.getClass().getName(), all it gets is the static type of the byte array. In order to interpret the data encoded in base-64 as something meaningful to your program, you need to know the format of underlying data transported as base-64. Once the bytes are delivered to you (in your case, that's encoded1 array of bytes) you need to decide what's inside, and act accordingly.
For example, if a serialized Java object is sent to you as base-64, you need to take encoded1, make an in-memory stream from it, and read the object using the regular serialization mechanism:
ByteArrayInputStream memStream = new ByteArrayInputStream(encoded1);
ObjectInputStream objStream = new ObjectInputStream(memStream);
Object attachedObject = objStream.readObject();

The encoding by Base64.encode() was successful if and only if size of encoded1 > size of obtained attachment1.
Please refer, to understand how the encoding works.
http://en.wikipedia.org/wiki/Base64
By the way, your last statement doesn't print the array content. It prints the name of the class to which encoded1 belongs to.

Best way for transfering files via socket in java

I have a BufferedReader object and a PrintWriter object. So I can work passing String objects made by json-io of any type (e.g.: List, Map, MyOwnClass)
My class have a byte[] attribute, this byte[] will keep a file bytes, such as an image.
The json generated of my class is very very big, obviously... Then i started to think that must have a better way to transfer files.
Should I change all the mechanism to transfer only byte[] instead of String? Does someone know what is the mechanism used by chat programs? Should I reserve the first 20 bytes of the array for the message identification?

I would write it to the socket in binary:
Assuming a class with one String and one byte[].
The String
The length of the String is written with DataOutputStream.writeInt(int) (or methods for smaller integers) and then OutputStream.write(byte[]) on the return value of String.getBytes(String) with the charset explicitly specified.
The byte[]
The length is written with DataOutputStream.writeInt(int) (or methods for smaller integers) and then OutputStream.write(byte[]) for the byte[] to transfer.
On the other side you would do the exact opposite of this procedure.
I chose this binary approach over JSON because even though you could transmit the byte[] with JSON almost as efficiently as in binary, it would defeat the very purpose of JSON: being human-readable.

How to convert byte array in String format to byte array?

I have created a byte array of a file.
FileInputStream fileInputStream=null;
File file = new File("/home/user/Desktop/myfile.pdf");
byte[] bFile = new byte[(int) file.length()];
try {
fileInputStream = new FileInputStream(file);
fileInputStream.read(bFile);
fileInputStream.close();
}catch(Exception e){
e.printStackTrace();
}
Now,I have one API, which is expecting a json input, there I have to put the above byte array in String format. And after reading the byte array in string format, I need to convert it back to byte array again.
So, help me to find;
1) How to convert byte array to String and then back to the same byte array?

The general problem of byte[] <-> String conversion is easily solved once you know the actual character set (encoding) that has been used to "serialize" a given text to a byte stream, or which is needed by the peer component to accept a given byte stream as text input - see the perfectly valid answers already given on this. I've seen a lot of problems due to lack of understanding character sets (and text encoding in general) in enterprise java projects even with experienced software developers, so I really suggest diving into this quite interesting topic. It is generally key to keep the character encoding information as some sort of "meta" information with your binary data if it represents text in some way. Hence the header in, for example, XML files, or even suffixes as parts of file names as it is sometimes seen with Apache htdocs contents etc., not to mention filesystem-specific ways to add any kind of metadata to files. Also, when communicating via, say, http, the Content-Type header fields often contain additional charset information to allow for correct interpretation of the actual Contents.
However, since in your example you read a PDF file, I'm not sure if you can actually expect pure text data anyway, regardless of any character encoding.
So in this case - depending on the rest of the application you're working on - you may want to transfer binary data within a JSON string. A common way to do so is to convert the binary data to Base64 and, once transferred, recover the binary data from the received Base64 string.
How do I convert a byte array to Base64 in Java?
is a good starting point for such a task.

String class provides an overloaded constructor for this.
String s = new String(byteArray, "UTF-8");
byteArray = s.getBytes("UTF-8");
Providing an explicit encoding charset is encouraged because different encoding schemes may have different byte representations. Read more here and here.
Also, your inputstream maynot read all the contents in one go. You have to read in a loop until there is nothing more left to be read. Read the documentation. read() returns the number of bytes read.
Reads up to b.length bytes of data from this input stream into an
array of bytes. This method blocks until some input is available

String.getBytes() and String(byte[] bytes) are methods to consider.

Convert byte array to String
String s = new String(bFile , "ISO-8859-1" );
Convert String to byte array
byte bArray[] =s.getBytes("ISO-8859-1");

Java String to Byte Conversion [duplicate]

This question already has an answer here:
Closed 11 years ago.
Possible Duplicate:
Java AES Encrypt Entire String
Im having problems with the conversions back and forth between strings and byte arrays.
Basically I've made a small program to encrypt and decrypt messages using AES.
After encrypting the message this happens:
byte[] result = cipher.doFinal(message.getBytes());
String stringResult = new String(result);
Which converts the encrypted message to a string.
Now my decryptor changes the string back to a byte using:
byte[] result = stringResult.getBytes();
but when it decrypts the message (depending on the message) it may not be able to. There appears to be a padding problem and the error that I get is:
Exception in thread "main" javax.crypto.BadPaddingException: Given final block not properly padded
Any ideas why this occurs?
One example when this occurs for sure is when the encryption key is "1231231231231231" and the message encrypted is "read".

You're using the platform default encoding - once to convert message to bytes, and once to then convert the arbitrary binary output of encryption back into a string. Both steps are problematic.
Firstly, it's best to use a fixed encoding which is known to cover the whole of Unicode when converting the string to bytes. UTF-8 is usually a good bet.
Then there's the matter of representing arbitrary binary data as text. This isn't text data represented in an encoding - it's binary data. Interpreting it as if it were text data will almost certainly lose information. You need something more robust, capable of round-tripping arbitrary binary data. Base64 is usually the way to go.
There's a public domain base64 encoder which works pretty well as far as I know. So your encryption code becomes:
byte[] result = cipher.doFinal(message.getBytes("UTF-8"));
String stringResult = Base64.encodeBytes(result);
The decrypting code would then be:
byte[] encrypted = Base64.decode(encryptedBase64);
byte[] decrypted = /* do the decryption here */
String message = new String(decrypted, "UTF-8");

Your encrypted bytes are binary data which are unlikely to survive conversion to a string and back. If it needs to be stored in a string then Base64 encode it.

Java Convert Asn.1 byte Array in convienient String for Browser

I try to convert a ASN.1 Byte Array into a String with Java. My results up to now:
byte[] asn = ocspResponse.getEncoded();
String liccert = new String(asn, "Cp850");
This String contains some String artifakts which are very disturbing:
Like this:
4¦20110416173611Z0üÏ0üi0:0
Is there a way to convert the byte Array like this:
RFMRIwEAYDVQQIEwlsb2NhbGhvc3QxFDASBgNV?

You should absolutely not convert arbitrary binary data to a string using the String constructor. That constructor is for taking binary data which is actually encoded text and building a string from it. Your data isn't really encoded text - it's just arbitrary binary data. Pretending it was originally text is a recipe for data loss.
The best approach is usually to Base64 encode it. There are plenty of third party libraries to do this, including Apache Commons Codec or this public domain encoder.
For example, using the latter:
String liccert = Base64.encodeBytes(asn);