如何从一个XML中提取字节数组并将其存储在Java中的另一个XML中

Question

So I am using DocumentBuilderFactory and DocumentBuilder to parse an xml. So it is DOM parser.

But what I am trying to do is extract byte-array data (its an image encoded in base64)

Store it in one object and later in code write it out to another xml encoded in base64.

What is the best way to store this in btw. Store it as string? or as ByteArray?

How can I extract byte array data in best way and write it out.

I am not experienced with this so wanted to get opinion from the group.

UPDATE: I am given XML I do not have control of incoming XML that comes in binary64 encoded

< byte-array >
  ... base64 encoded image ...
< /byte-array >

Using parser I have I need to store this node and question is should that be byte or string and then writing it out to another node in new xml. again in base64 encoding.

thanks

Answer 1

The image should be stored in the first xml as a string. Perhaps something like this:

<img src="data:image/gif;base64,sssssssssssss"/>

If you need to write the same data to the second xml just use the same string which is already encoded. If you need to change the image. Get the attribute ( element.getAttribute("src") ), decode it with one of the many libraries ( apache commons codec ) and then reencode it as a string for the second xml.

UPDATE RESPONSE:

As to your update. Inside the <byte-array> element you should have plain text. It could be stored as text and then used as text in the second xml.

Answer 2

Base64 encoding is generally used when you need transport the data over text based protocols like http. What Base64 encoding does is encodes the binary data into set of characters which can be sent over text based protocol without any encoding/decoding problems.

Not sure if you are sending the xml over the wire, but you can use any of the folloiwng methods

1. Send the base64 string as simple string. But in this case the onus of encoding and decoding will on sending and receiving application programs.

2. Use standard base64Binary xml type . In this case, the parser will take care of decoding the string.

Answer 3

There's a class in Apache Commons that will help you ensure data integrity with Base64:

import org.apache.commons.codec.binary.Base64;

String yourString = "testing";
byte[] encoded = Base64.encodeBase64(yourString.getBytes());

http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html

Although, Base64 data is simply alpha characters in addition to + and / , so there shouldn't be any data loss if you store it in a String.