// call this method to write the description to the file
// the file pointer must be already positioned
// the description must have been set
private void writeDescription() throws IOException {
if (description.length() > DESCRIPTION_LENGTH)
description = description.substring(0, DESCRIPTION_LENGTH);
outStream.writeChars(description);
for (int j = 0; j < (DESCRIPTION_LENGTH - description.length()); j++) outStream.writeChar(' ');
}
private void write(String partnum, String partdesc, int qty, int ucost) throws IOException {
StringBuffer sb = new StringBuffer(partnum);
if (sb.length() > PNUMLEN) sb.setLength(PNUMLEN);
else if (sb.length() < PNUMLEN) {
int len = PNUMLEN - sb.length();
for (int i = 0; i < len; i++) sb.append(" ");
}
raf.writeChars(sb.toString());
sb = new StringBuffer(partdesc);
if (sb.length() > DESCLEN) sb.setLength(DESCLEN);
else if (sb.length() < DESCLEN) {
int len = DESCLEN - sb.length();
for (int i = 0; i < len; i++) sb.append(" ");
}
raf.writeChars(sb.toString());
raf.writeInt(qty);
raf.writeInt(ucost);
}
// call this method to write the column names to the file
// the file pointer must be already positioned
private void writeColumnNames(ArrayList names) throws IOException {
String column;
for (int i = 0, numCols = names.size(); i < numCols; i++) {
column = (String) names.get(i);
if (column.length() > COLUMN_LENGTH) column = column.substring(0, COLUMN_LENGTH);
outStream.writeChars(column);
for (int j = 0; j < (COLUMN_LENGTH - column.length()); j++) outStream.writeChar(' ');
}
}
// write a String to the file
public boolean writeString(String str) {
if (false == this.startedFlag) {
System.err.println("TcpFileReadWriter: this object is closed already");
return false;
}
try {
raf.writeChars(str);
} catch (Exception e) {
e.printStackTrace();
System.err.println("TCPFileReadWriter: writeString fail!!");
return false;
}
return true;
}
public void writeOutput() throws IOException {
//noinspection ResultOfMethodCallIgnored
new File(path).mkdirs();
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(path + "/" + getExportFileName(), "rw");
randomAccessFile.setLength(0);
randomAccessFile.writeChars(output);
} finally {
try {
if (randomAccessFile != null) {
randomAccessFile.close();
}
} catch (IOException e) {
// do nothing
}
}
}
/** sample usage and testing */
public static void main(String[] args) {
Itemset is1 = new Itemset();
is1.add(1);
is1.add(2);
Itemset is2 = new Itemset();
is2.add(3);
is2.add(2);
Itemset is3 = new Itemset();
is3.add(3);
is3.add(1);
Itemset is4 = new Itemset();
is4.add(33);
is4.add(3);
ArrayList colNames = new ArrayList(3);
colNames.add("cheese");
colNames.add("pizza");
colNames.add("beer");
System.out.println("\n\nCreating invalid database:");
try {
RandomAccessFile invalid = new RandomAccessFile("invalid.db", "rw");
invalid.writeChars(ID + " - a bogus file that looks like a valid one");
invalid.close();
} catch (Exception e) {
System.out.println("Shouldn't have happened: " + e);
}
System.out.println("\n\nCreating corrupted database:");
try {
DBWriter corrupted = new DBWriter("corrupted.db");
try {
corrupted.addRow(is1);
} catch (DBException e) {
System.out.println(e);
}
corrupted.setDescription("a corrupted database");
corrupted.setColumnNames(colNames);
corrupted.addRow(is1);
corrupted.setDescription("a corrupted database - 2");
corrupted.setColumnNames(colNames);
corrupted.addRow(is2);
corrupted.setDescription("a corrupted database - 3");
corrupted.addRow(is3);
try {
corrupted.addRow(is4);
} catch (DBException e) {
System.out.println(e);
}
corrupted.close();
System.out.println("corrupting file");
RandomAccessFile raf = new RandomAccessFile("corrupted.db", "rw");
raf.seek(770);
// replace the 2 in the second itemset with a 3
raf.writeInt(3);
raf.close();
} catch (Exception e) {
System.out.println("Shouldn't have happened: " + e);
}
System.out.println("\n\nCreating empty database:");
try {
DBWriter empty = new DBWriter("empty.db");
empty.setDescription("an empty database");
empty.setColumnNames(colNames);
empty.close();
} catch (Exception e) {
System.out.println("Shouldn't have happened: " + e);
}
System.out.println("\n\nCreating correct database:");
try {
DBWriter correct = new DBWriter("correct.db");
correct.setDescription("a correct database");
correct.setColumnNames(colNames);
correct.addRow(is1);
correct.setDescription("a correct database - 2");
correct.setColumnNames(colNames);
correct.addRow(is2);
correct.setDescription("a correct database - 3");
correct.addRow(is3);
correct.close();
correct = new DBWriter("correct.db");
correct.setColumnNames(colNames);
correct.addRow(is1);
correct.setDescription("a correct database - 4");
correct.setColumnNames(colNames);
correct.addRow(is2);
correct.setDescription("a correct database - 5");
correct.addRow(is3);
correct.close();
} catch (Exception e) {
System.out.println("Shouldn't have happened: " + e);
}
System.out.println("\n\nOpening and closing DBWriter:");
try {
DBWriter bummer = new DBWriter("bummer.db");
bummer.close();
} catch (Exception e) {
System.out.println("Shouldn't have happened: " + e);
}
}
/**
* Set the column names for the database.
*
* @param names the column names
* @exception IOException from library call
* @exception DBException size of <code>names</code> does not match number of columns
*/
public void setColumnNames(ArrayList names) throws IOException, DBException {
long namesSize = names.size();
if (wroteColumnNames == false) {
numColumns = namesSize;
// ID
outStream.writeChars(ID);
// version number
outStream.writeInt(1);
outStream.writeInt(0);
outStream.writeInt(0);
headerSize =
COLUMN_NAME_OFFSET
+ COLUMN_SIZE * numColumns
+ ID_SIZE
+ DESCRIPTION_SIZE
+ ID_SIZE
+ CRC_SIZE;
outStream.writeLong(headerSize);
// number of rows
outStream.writeLong(0);
// number of columns
outStream.writeLong(numColumns);
// columns
writeColumnNames(names);
// rest of the header
outStream.writeChars(ID);
// check if description has been set, otherwise fill in with blanks
if (description != null) writeDescription();
else {
description = " ";
writeDescription();
}
outStream.writeChars(ID);
// CRC
outStream.writeInt(0);
wroteColumnNames = true;
} else {
if (namesSize != numColumns) throw new DBException("Cannot change the number of columns");
else {
if (needReposition == false) {
lastPosition = outStream.getFilePointer();
needReposition = true;
}
outStream.seek(COLUMN_NAME_OFFSET);
writeColumnNames(names);
}
}
}
/* @see java.io.DataOutput.writeChars(String) */
public void writeChars(String s) throws IOException {
raf.writeChars(s);
}