Question

I am using Apache poi 3.8 for reading xls file, but i got exception:

        java.io.IOException: Unable to read entire header; 0 bytes read; expected 512 bytes
        at org.apache.poi.poifs.storage.HeaderBlock.alertShortRead(HeaderBlock.java:226)
        at org.apache.poi.poifs.storage.HeaderBlock.readFirst512(HeaderBlock.java:207)
        at org.apache.poi.poifs.storage.HeaderBlock.<init>(HeaderBlock.java:104)
        at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:138)

used code sample:

     FileInputStream myInput = new FileInputStream(excelFilePathWithExtension);
     logger.debug("FileInputStream::"+myInput);

     POIFSFileSystem myFileSystem = new POIFSFileSystem(myInput);
     logger.debug("POIFSFileSystem::"+myFileSystem);

     Workbook workbook = WorkbookFactory.create(myFileSystem);

please help me?

Answer 1

If we take a look at the HeaderBlocks class, we can see these blocks :

public HeaderBlock(InputStream stream) throws IOException {
    // Grab the first 512 bytes
    // (For 4096 sized blocks, the remaining 3584 bytes are zero)
    // Then, process the contents
    this(readFirst512(stream));
    ...
}

The constructor you used will read the first 512 bytes of your inputstream then call a private constructor.

And the readFirst512 method throw an exception if there is not enough bytes to read.

Also, the POI’s document say that a POI file system structure starts starts with a header block of 512 bytes.

So… It seems that your file is not big enough for POI.