How to convert byte that are in a file to object in java?

Question

I have a hadoop job for which its final output is the following

String myKey = "myKey";
context.write(myKey, myObjectWritable.toByteArray());

My output file look like the following

myKey/t00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

my question is how do I convert the bytes in string to a byte[] since the file is consist of string and bytes that is written as string.

    try (BufferedReader br = new BufferedReader(new FileReader("my_map_reduce_file"))) {
        String line;
        while ((line = br.readLine()) != null) {
            String[] x = line.split("\t");

            // how do I convert x[1] to byte[]

       }

Possible duplicate of [How to convert Java String into byte\[\]?](https://stackoverflow.com/questions/18571223/how-to-convert-java-string-into-byte) — smac89, Oct 09 '19 at 18:36
If you write the file as binary (non-string), read the file as a binary(non-binary). the InputStream and OutputStream classes let you read() and write() bytes. All that said, if the data is actually a string, use TextReader and TextWriter and let the built-in behavior work for you — Gus, Oct 09 '19 at 18:39

lotor · Answer 1 · 2019-10-09T18:41:26.143

To read you should revert the write process. If you invented writing yourself - do reading yourself. Otherwise consider ObjectOutputStream for writing, ObjectInputStream for reading and the whole Serializable protocol.

Example for writing

        try(ObjectOutputStream stream = new ObjectOutputStream(new FileOutputStream(file))){
            stream.writeObject("Key");
            stream.writeObject("Value");
            stream.flush();
        }

and for corresponding reading

        try(ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(file))){
            String key = (String) objectInputStream.readObject();
            String value = (String) objectInputStream.readObject();
        }

These guys will do all the job for any object, whos class implements Serializable, like HashMap and most of the util things you mostly use.

score 0 · Answer 2 · answered Oct 09 '19 at 18:37

0

String mykey = "myKey";
byte[] mykey_byte_array = mykey.getBytes(StandardCharsets.UTF_8); 
System.out.println("contents of byte array " + Arrays.toString(mykey_byte_array));

answered Oct 09 '19 at 18:37

Karan

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How to convert byte that are in a file to object in java?

2 Answers2