Provide log if the two files are identical and has same contents in Java

Question

I have below code where i am reading the file from particular directory, processing it and once processed i am moving the file to archive directory. This is working fine. I am receiving new file everyday and i am using Control-M scheduler job to run this process.

Now in next run i am reading the new file from that particularly directory again and checking this file with the file in the archive directory and if the content is different then only process the file else dont do anything. There is shell script written to do this job and we dont see any log for this process.

Now i want to produce log message in my java code if the files are identical from the particular directory and in the archive directory then generate log that 'files are identical'. But i dont know exactly how to do this. I dont want to write the the logic to process or move anything in the file ..i just need to check the files are equal and if it is then produce log message. The file which i recieve are not very big and the max size can be till 10MB.

Below is my code:

        for(Path inputFile : pathsToProcess) {
            // read in the file:
            readFile(inputFile.toAbsolutePath().toString());
            // move the file away into the archive:
            Path archiveDir = Paths.get(applicationContext.getEnvironment().getProperty(".archive.dir"));
            Files.move(inputFile, archiveDir.resolve(inputFile.getFileName()),StandardCopyOption.REPLACE_EXISTING);
        }
        return true;
    }

    private void readFile(String inputFile) throws IOException, FileNotFoundException {
        log.info("Import " + inputFile);

        try (InputStream is = new FileInputStream(inputFile);
                Reader underlyingReader = inputFile.endsWith("gz")
                        ? new InputStreamReader(new GZIPInputStream(is), DEFAULT_CHARSET)
                        : new InputStreamReader(is, DEFAULT_CHARSET);
                BufferedReader reader = new BufferedReader(underlyingReader)) {

            if (isPxFile(inputFile)) {
                Importer.processField(reader, tablenameFromFilename(inputFile));
            } else {
                Importer.processFile(reader, tablenameFromFilename(inputFile)); 
            }

        }
        log.info("Import Complete");
    }       

}

Answer 1

Based on the limited information about the size of file or performance needs, something like this can be done. This may not be 100% optimized, but just an example. You may also have to do some exception handling in the main method, since the new method might throw an IOException:

import org.apache.commons.io.FileUtils;  // Add this import statement at the top


// Moved this statement outside the for loop, as it seems there is no need to fetch the archive directory path multiple times.
Path archiveDir = Paths.get(applicationContext.getEnvironment().getProperty("betl..archive.dir"));  

for(Path inputFile : pathsToProcess) {

    // Added this code
    if(checkIfFileMatches(inputFile, archiveDir); {
        // Add the logger here.
    }
    //Added the else condition, so that if the files do not match, only then you read, process in DB and move the file over to the archive. 
    else {
        // read in the file:
        readFile(inputFile.toAbsolutePath().toString());
        Files.move(inputFile, archiveDir.resolve(inputFile.getFileName()),StandardCopyOption.REPLACE_EXISTING);
    }       
}


//Added this method to check if the source file and the target file contents are same.
// This will need an import of the FileUtils class. You may change the approach to use any other utility file, or read the data byte by byte and compare. If the files are very large, probably better to use Buffered file reader.
    private boolean checkIfFileMatches(Path sourceFilePath, Path targetDirectoryPath) throws IOException {
        if (sourceFilePath != null) {  // may not need this check
            File sourceFile = sourceFilePath.toFile();
            String fileName = sourceFile.getName();

            File targetFile = new File(targetDirectoryPath + "/" + fileName);

            if (targetFile.exists()) {
                return FileUtils.contentEquals(sourceFile, targetFile);
            }
        }
        return false;
    }