/**
* Validates the structure of the merged csv files.
*
* @param mFiles List of MasterFiles to check
* @return Returns true if the data structure of all given files matches. Throws an user exception
* (MergeException) otherwise.
* @throws MergeException
*/
public static boolean dataStructureMatch(List<MasterFile> mFiles) throws MergeException {
String[] headers = null;
String headerLine = "";
String currFile = "";
BufferedReader reader;
FileInputStream fis;
boolean firstRun = true;
try {
int maxHeaderSize = 0;
for (MasterFile mFile : mFiles) {
String fPath = mFile.getLocalAbsolutePath();
currFile = fPath;
File csvFile = new File(fPath);
FileReader freader = new FileReader(csvFile);
CSVReader csvreader = new CSVReader(freader, '\t', CSVWriter.NO_QUOTE_CHARACTER);
headers = csvreader.readNext();
if (headers != null) {
if (headers.length != maxHeaderSize) {
maxHeaderSize = headers.length;
// get header line
fis = new FileInputStream(fPath);
reader = new BufferedReader(new InputStreamReader(fis));
headerLine = reader.readLine();
reader.close();
if (!firstRun) {
throw new MergeException(
"Data structure has changed within the given interval. File:"
+ mFile.getName()
+ "; Time tag of the file:"
+ mFile.getCreated()
+ ". The number of columns has changed.",
1);
}
firstRun = false;
}
} else {
throw new MergeException("Error reading csv file header: " + currFile, 1);
}
csvreader.close();
}
if (maxHeaderSize == 0 || headerLine.equals("")) {
throw new MergeException("Zero length header in csv file!", 1);
}
return true;
} catch (FileNotFoundException ex) {
throw new MergeException("CSV file not found. " + currFile + " " + ex.getMessage(), 1);
} catch (IOException ex) {
throw new MergeException("Error reading csv file: " + currFile + " " + ex.getMessage(), 1);
}
}
/**
* @param filePaths - list of files to merge
* @return header line with the most columns
* @throws Exception
*/
private static String getLongestHeaders(List<MasterFile> mFiles) throws Exception {
String[] headers = null;
String headerLine = "";
String currFile = "";
BufferedReader reader;
FileInputStream fis;
try {
int maxHeaderSize = 0;
for (MasterFile mFile : mFiles) {
String fPath = mFile.getLocalAbsolutePath();
currFile = fPath;
File csvFile = new File(fPath);
FileReader freader = new FileReader(csvFile);
CSVReader csvreader = new CSVReader(freader, '\t', CSVWriter.NO_QUOTE_CHARACTER);
headers = csvreader.readNext();
if (headers != null) {
if (headers.length > maxHeaderSize) {
maxHeaderSize = headers.length;
// get header line
fis = new FileInputStream(fPath);
reader = new BufferedReader(new InputStreamReader(fis));
headerLine = reader.readLine();
reader.close();
}
} else {
throw new Exception("Error reading csv file header: " + currFile);
}
csvreader.close();
}
if (maxHeaderSize == 0 || headerLine.equals("")) {
throw new Exception("Zero length header in csv file!");
}
return headerLine;
} catch (FileNotFoundException ex) {
throw new Exception("CSV file not found. " + currFile + " " + ex.getMessage());
} catch (IOException ex) {
throw new Exception("Error reading csv file: " + currFile + " " + ex.getMessage());
}
}
public static void mergeFiles(List<MasterFile> masterFiles, String mergedPath, String mergedName)
throws MergeException {
BufferedReader reader = null;
String headerLine = "";
// create output file
File folder = new File(mergedPath);
// if the directory does not exist, create it
if (!folder.exists()) {
folder.mkdirs();
}
File outFile = new File(mergedPath + File.separator + mergedName);
int i = 0;
FileChannel out = null;
FileOutputStream fout = null;
try {
// validate merged csv files
dataStructureMatch(masterFiles);
} catch (MergeException ex) {
throw ex;
}
for (MasterFile mFile : masterFiles) {
FileInputStream fis = null;
String fPath = mFile.getLocalAbsolutePath();
try {
File file = new File(fPath);
// retrieve file header
fis = new FileInputStream(file);
reader = new BufferedReader(new InputStreamReader(fis));
headerLine = reader.readLine();
if (headerLine == null) {
continue;
}
// write header from first file and retrieve filechannel
if (i == 0) {
fout = new FileOutputStream(outFile);
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(fout));
bw.write(headerLine);
bw.newLine();
bw.flush();
out = fout.getChannel();
}
// write to outFile using NIO
FileChannel in = fis.getChannel();
long pos = 0;
// set position according to header (first run is set by writer)
pos = headerLine.length() + 2; // +2 because of NL character
for (long p = pos, l = in.size(); p < l; ) {
p += in.transferTo(p, l - p, out);
}
i++;
} catch (FileNotFoundException ex) {
Logger.getLogger(CsvFileMerger.class.getName()).log(Level.SEVERE, null, ex);
throw new MergeException("File not found. " + ex.getMessage());
} catch (IOException ex) {
Logger.getLogger(CsvFileMerger.class.getName()).log(Level.SEVERE, null, ex);
throw new MergeException("Error merging files. " + ex.getMessage());
} finally {
try {
reader.close();
fis.close();
} catch (IOException ex) {
Logger.getLogger(CsvFileMerger.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}