Junit testing for base64 encoded string

Question

I'm trying to read the contents of a PDF using Apache's PDFBox and encode it in base64 so I can stream it to elsewhere. To encode it I use the Apache commons Base64OutputStream class. Like so, ``` ByteArrayOutputStream byteOutput = new ByteArrayOutputStream(); Base64OutputStream base64Output = new Base64OutputStream(byteOutput); List pages = pdfDocument.getDocumentCatalog().getAllPages(); Iterator iter = pages.iterator(); while (iter.hasNext()) { PDPage page = (PDPage) iter.next(); PDResources resources = page.getResources(); Map<String, PDXObjectImage> pageImages = resources.getImages(); if (pageImages != null) { Iterator imageIter = pageImages.keySet().iterator(); while (imageIter.hasNext()) { String key = (String) imageIter.next(); PDXObjectImage image = (PDXObjectImage) pageImages .get(key); image.write2OutputStream(base64Output); } } } String base64 = new String(byteOutput.toByteArray()); ``` It seems to be encoding it but I need to verify it by writing a junit test to validate t…

Accepted Answer

By default `Base64OutputStream` is using CHUNK_SIZE = 76, and CHUNK_SEPARATOR = {'', '
'}. Regular expression you are using to test if given string is a BASE64 encoded doesn't account for that.

Regular expression to match chunked BASE64 (with given chunk size 64 and separator 
) string could look like this:

```
"^(([\w+/]{4}){19}
)*(([\w+/]{4})*([\w+/]{4}|[\w+/]{3}=|[\w+/]{2}==))$"
```

Junit testing for base64 encoded string

Solution

Problem