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Java CSV parsing with Apache Commons CSV parser 

Dr. Xi
Joined:
04/09/2007
Posts:
753

June 21, 2011 15:41:51    Last update: June 22, 2011 11:33:36
Demo code for CSV parsing with Apache Commons CSV parser.
  1. Java code: 
    import java.io.*;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVStrategy;

public class CSVParseDemo {
    public static void main(String[] args) throws IOException {
	if (args.length < 1) {
	    System.out.println("Usage: java CSVParseDemo <csv_file>");
	    return;
	}

	CSVParser parser = new CSVParser(new FileReader(args[0]), CSVStrategy.EXCEL_STRATEGY);
	String[] values = parser.getLine();
	while (values != null) {
	    printValues(parser.getLineNumber(), values);
	    values = parser.getLine();
	}
    }

    private static void printValues(int lineNumber, String[] as) {
	System.out.println("Line " + lineNumber + " has " + as.length + " values:");
	for (String s: as) {
	    System.out.println("\t|" + s + "|");
	}
	System.out.println();
    }
}

  2. Test with a simple CSV file: 
    psmith01,CLASS2B,Peter Smith 1,YEAR2,1,N,ADVANCED,STAFF,1,Y,Y
smehta,CLASS3G,Smeeta Mehta,LOCAL,1,Y,STANDARD,PUPIL,2.1,N,Y

    Result: 
    Line 1 has 11 values:
	|psmith01|
	|CLASS2B|
	|Peter Smith 1|
	|YEAR2|
	|1|
	|N|
	|ADVANCED|
	|STAFF|
	|1|
	|Y|
	|Y|

Line 2 has 11 values:
	|smehta|
	|CLASS3G|
	|Smeeta Mehta|
	|LOCAL|
	|1|
	|Y|
	|STANDARD|
	|PUPIL|
	|2.1|
	|N|
	|Y|

    The parser worked correctly.

  3. Test with a more complicated CSV file: 
    "psmith01 abc", "CLASS2B            "    , " Peter, Smith 1", "\", YEAR2 \""
" smehta ' \", \\, "   ,     "CLASS3G \\"
" smehta ' \", \\, "   ,     "CLASS3G \"

    Result: 
    Line 1 has 4 values:
	|psmith01 abc|
	|CLASS2B            |
	| Peter, Smith 1|
	|", YEAR2 "|

Line 2 has 2 values:
	| smehta ' ", \\, |
	|CLASS3G \\|

Exception in thread "main" java.io.IOException: (startline 2)eof reached before encapsulated token finished
	at org.apache.commons.csv.CSVParser.encapsulatedTokenLexer(CSVParser.java:510)
	at org.apache.commons.csv.CSVParser.nextToken(CSVParser.java:365)
	at org.apache.commons.csv.CSVParser.getLine(CSVParser.java:239)
	at CSVParseDemo.main(CSVParseDemo.java:16)

    The third line is invalid input, but throwing a Java IOException is a bit grave. Also, the parser is not able to escape a backslash.

  4. Add a new line in item two: 
    "One", "Two
", "Three"

    Result: 
    Line 2 has 3 values:
	|One|
	|Two
|
	|Three|

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