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FastCSV FastCSV

FAQ

General questions

How to contribute?

Contributions are welcome! Please refer to the Contribution Guide.

Where to ask questions? Where to get help?

If you have questions about FastCSV, please ask them on GitHub Discussions.

How to suggest a feature?

Feature requests can be submitted via the GitHub issue tracker. Make sure that the feature would align with the goals of FastCSV.

How to report a bug?

If you encounter a bug, please report it by creating a new issue on the GitHub issue tracker. Make sure to include a JUnit test that reproduces the issue. This helps to understand the problem and to verify the fix.

Please do not report security vulnerabilities through public GitHub issues, discussions, or pull requests.

How to report a security vulnerability?

If you discover a security vulnerability, please report it via https://github.com/osiegmar/FastCSV/security.

Do I need a CSV library?

Java does not provide built-in support for reading and writing CSV files.

You may wonder why you need a CSV library at all, since CSV files are just text files separated by commas – right? Well, not so fast! 😉

Think about how to handle:

  • enclosed and non-enclosed fields
  • fields containing commas, line breaks or (escaped) quotes
  • different line endings
  • empty lines or empty fields
  • optional headers
  • BOM (Byte Order Mark) headers
  • large files/fields without running out of memory
  • garbled data (e.g. data outside of quotes)
  • comments

FastCSV handles all these cases and more, so you don’t have to worry about them. With only a few kilobytes in size and zero dependencies, FastCSV is a great choice for reading and writing CSV files in Java.

While most parts of this documentation are focused on the features of FastCSV, this section explicitly addresses some questions about features that are not supported by FastCSV or how to achieve certain tasks.

Encoding

Does FastCSV support mixed encodings?

FastCSV supports reading and writing CSV files in any encoding supported by Java.

However, it does not support mixed encodings within a single CSV file. The encoding of the file must be consistent.

Control characters

Does FastCSV support field separators with multiple characters?

While CSV stands for “Comma-Separated Values” and the RFC specifies only the comma as the field separator, FastCSV allows configuring the field separator to support real-world CSV files that may use different separators like semicolon or tab.

Although it does not support field separators with multiple characters (each).

Does FastCSV support mixed field separators?

The use of mixed field separators (e.g., comma and semicolon) within a single CSV file is not supported by FastCSV.

The configured field separator (comma by default) is used for the entire CSV file.

Does FastCSV support field encapsulation with multiple characters?

While the RFC specifies only double quotes to encapsulate fields, FastCSV allows configuring the character to support real-world CSV files that may use different characters, like single quotes.

However, it does not support field encapsulation with multiple characters (each).

Does FastCSV support mixed field encapsulation?

The use of mixed field encapsulation (e.g., double quotes and single quotes) within a single CSV file is not supported by FastCSV.

The configured quote character (double quote by default) is used for the entire CSV file.

Does FastCSV allow configuring the escape character?

The RFC defines that double quotes are escaped by doubling them. A string a " b would be written as "a "" b".

If you configure FastCSV to use a different quote character, it will also be escaped by doubling it. A string a ' b would be written as 'a '' b', if you configure the quote character to be a single quote.

FastCSV does not support configuring a different escape character.

See also: https://github.com/osiegmar/FastCSV/issues/103

Auto conversion/mapping

Does FastCSV support automatic bean mapping?

See Bean Mapping example for more information.

Does FastCSV support automatic type conversion?

The CSV format does not specify data types. FastCSV reads and writes all fields as strings.

When writing CSV records, you have to convert fields to strings yourself.

When reading CSV records, you have the following options:

  • Use the CsvRecord API to access fields as strings and convert them to the desired type. You may also combine this with the Java stream API (see above).
  • Implement a custom CsvCallbackHandler to access raw data (char[]). Checkout the Reader with custom CallBackHandler example.