opencsv

Frequently Asked Questions

General

1. What is opencsv?
2. Where can I get it?
3. What features does opencsv support?

Reading and Writing

1. How do I read and parse a CSV file?
2. Can I use my own separators and quote characters?
3. Can I write csv files with opencsv?
4. Can I dump out SQL tables to CSV?
5. Is there a way to bind my CSV file to a list of Javabeans?

Other Stuff

1. Can I use opencsv in my commercial applications?
2. Can I get the source? More example code?
3. How can I use it in my Maven projects?
4. Who maintains opencsv?

opencsv Development Stuff

1. Is there a snapshot Maven repo for opencsv?
2. I'm an opencsv developer, how do you go about releasing a new version?

General

What is opencsv?

opencsv is a very simple csv (comma-separated values) parser library for Java. It was developed because all of current csv parsers I've come across don't have commercial-friendly licenses.

Where can I get it?

Source and binaries are available from  Sourceforge. You can check out the  javadocs online.

What features does opencsv support?

opencsv supports all the basic csv-type things you're likely to want to do:

• Arbitrary numbers of values per line
• Ignoring commas in quoted elements
• Handling quoted entries with embedded carriage returns (ie entries that span multiple lines)
• Configurable separator and quote characters (or use sensible defaults)
• Read all the entries at once, or use an Iterator style model
• Creating csv files from String[] (ie. automatic escaping of embedded quote chars)

Reading and Writing

How do I read and parse a CSV file?

If you want to use an Iterator style pattern, you might do something like this:

    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
    String [] nextLine;
    while ((nextLine = reader.readNext()) != null) {
        // nextLine[] is an array of values from the line
        System.out.println(nextLine[0] + nextLine[1] + "etc...");
    }
           

Or, if you might just want to slurp the whole lot into a  List, just call  readAll()...

    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
    List myEntries = reader.readAll();
           

which will give you a  List of  String[] that you can iterate over. If all else fails, check out the  Javadoc.

Can I use my own separators and quote characters?

Yes. There are constructors that cater for supplying your own separator and quote characters. Say you're using a tab for your separator, you can do something like this:

    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"), '\t');
               

And if you single quoted your escaped characters rather than double quote them, you can use the three arg constructor:

    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"), '\t', '\'');
           

You may also skip the first few lines of the file if you know that the content doesn't start till later in the file. So, for example, you can skip the first two lines by doing:

    CSVReader reader = new CSVReader(new FileReader("yourfile.csv"), '\t', '\'', 2);
           

Can I write csv files with opencsv?

Yes. There is a CSVWriter in the same package that follows the same semantics as the CSVReader. For example, to write a tab separated file:

     CSVWriter writer = new CSVWriter(new FileWriter("yourfile.csv"), '\t');
     // feed in your array (or convert your data to an array)
     String[] entries = "first#second#third".split("#");
     writer.writeNext(entries);
	writer.close();
               

If you'd prefer to use your own quote characters, you may use the three arg version of the constructor, which takes a quote character (or feel free to pass in CSVWriter.NO_QUOTE_CHARACTER).

You can also customise the line terminators used in the generated file (which is handy when you're exporting from your Linux web application to Windows clients). There is a constructor argument for this purpose.

Can I dump out SQL tables to CSV?

Yes you can. Sean Sullivan added a neat feature to CSVWriter so you can pass  writeAll() a ResultSet.

java.sql.ResultSet myResultSet = ....
writer.writeAll(myResultSet, includeHeaders);
           

Is there a way to bind my CSV file to a list of Javabeans?

Yes there is. Kyle Miller added a new set of classes to allow you to bind a CSV file to a list of JavaBeans based on column name, column position, or a custom mapping strategy. You can find the new classes in the  au.com.bytecode.opencsv.bean package. Here's how you can map to a java bean based on the field positions in your CSV file:

ColumnPositionMappingStrategy strat = new ColumnPositionMappingStrategy();
strat.setType(YourOrderBean.class);
String[] columns = new String[] {"name", "orderNumber", "id"}; // the fields to bind do in your JavaBean
strat.setColumnMapping(columns);

CsvToBean csv = new CsvToBean();
List list = csv.parse(strat, yourReader);
           

For more detailed examples, check out the test cases for each of the available mapping strategies under the /test/au/com/bytecode/opencsv/bean/.

Other Stuff

Can I use opencsv in my commercial applications?

Yes. opencsv is available under a commercial-friendly Apache 2.0 license. You are free to include it in your commericial applications without any fee or charge, and you are free to modify it to suit your circumstances. To find out more details of the license, read the  Apache 2.0 license agreement.

Can I get the source? More example code?

Yes. The download from the SourceForge page includes the full source in the  /src directory. It's just a few files, so go crazy. There is also a sample addressbook csv reader in the  /examples directory. And for extra marks, there's a JUnit test suite in the  /test directory.

How can I use it in my Maven projects?

Add a dependency element to your pom:

<dependency>
	<groupId>net.sf.opencsv</groupId>
	<artifactId>opencsv</artifactId>
	<version>2.0</version>
</dependency>
				

Who maintains opencsv?

opencsv was developed in a couple of hours by Glen Smith. You can read his  blog for more info and contact details. Kyle Miller contributed the bean binding work, Scott Conway has done tons of bug fixing, and Sean Sullivan is the current maintainer of the project.

If you've found a bug, you can report it on the  project page at Sourceforge. Please post a sample file that demonstrates your issue. For bonus marks, post a patch too. :-)

opencsv Development Stuff

Is there a snapshot Maven repo for opencsv?

Yes. We're using a  repo provided by the good folk at Sonatype.

I'm an opencsv developer, how do you go about releasing a new version?

Here's the general process for a release:

• First you talk to everyone else on the team to make sure they're on the same page.
• After that you can follow the detailed instructions found on the Sonatype site to get a JIRA username/password
• As part of that process, you'll need to add your JIRA account name as a comment to our existing JIRA ticket.
• Once you have access, change your Maven settings.xml on your local machine per Step 7a.1. in the Sonatype setup doc.
• With all that in place, you can do a "mvn deploy" to release snapshots, or if you're ready to release, create a new branch, set the version in the POM, and "mvn release" again.
• For prod releases, the release process puts things in the staging Nexus at Sonatype. It's a manual step from there to release (see step 8 of the Sonatype setup doc). First you have to "Close" the release in the staging repo (which checks the signatures and metadata), then they sent you an email, then you have to "Release" the release to central.
• Finally, update the Sourceforge website with the latest Javadoc by using a "mvn site:deploy" (Details here)