I want to read the PDF file using hadoop, how it is possible? I only know that hadoop can process only txt files, so is there anyway to parse the PDF files to txt.
Give me some suggestion.
An easy way would be to create a SequenceFile to contain the PDF files. SequenceFile is a binary file format. You could make each record in the SequenceFile a PDF. To do this you would create a class derived from Writable which would contain the PDF and any metadata that you needed. Then you could use any java PDF library such as PDFBox to manipulate the PDFs.
Processing PDF files in Hadoop can be done by extending FileInputFormat Class. Let the class extending it be WholeFileInputFormat. In the WholeFileInputFormat class you override the getRecordReader() method. Now each pdf will be received as an Individual Input Split. Then these individual splits can be parsed to extract the text. This link gives a clear example of understanding how to extend FileInputFormat.
来源：https://stackoverflow.com/questions/9290119/how-to-access-and-manipulate-pdf-files-datas-in-hadoop