README

kotlin-csv

Version
License: Apache License 2.0
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CodeFactor
Pure Kotlin CSV Reader/Writer.

Design goals

1. Simple interface

  • easy to setup
  • use DSL so easy to read

2. Automatic handling of I/O

  • in Java, we always need to close file. but it's boilerplate code and not friendly for non-JVM user.
  • provide interfaces which automatically close file without being aware.

3. Multiplatform

  • Kotlin Multiplatform projects support.

Usage

Download

Gradle

// Gradle Kotlin DSL
implementation("com.github.doyaaaaaken:kotlin-csv-jvm:1.9.2") // for JVM platform
implementation("com.github.doyaaaaaken:kotlin-csv-js:1.9.2") // for Kotlin JS platform
// Gradle Groovy DSL
implementation 'com.github.doyaaaaaken:kotlin-csv-jvm:1.9.2' // for JVM platform
implementation 'com.github.doyaaaaaken:kotlin-csv-js:1.9.2' // for Kotlin JS platform

Maven

<dependency>
<groupId>com.github.doyaaaaaken</groupId>
<artifactId>kotlin-csv-jvm</artifactId>
<version>1.9.2</version>
</dependency>
<dependency>
<groupId>com.github.doyaaaaaken</groupId>
<artifactId>kotlin-csv-js</artifactId>
<version>1.9.2</version>
</dependency>

kscript

@file:DependsOn("com.github.doyaaaaaken:kotlin-csv-jvm:1.9.2") // for JVM platform
@file:DependsOn("com.github.doyaaaaaken:kotlin-csv-js:1.9.2") // for Kotlin JS platform

Examples

CSV Read examples

Simple case
You can read csv file from String, java.io.File or java.io.InputStream object. No need to do any I/O handling. (No need to call use, close and flush method.)
// read from `String`
val csvData: String = "a,b,c\nd,e,f"
val rows: List<List<String>> = csvReader().readAll(csvData)
// read from `java.io.File`
val file: File = File("test.csv")
val rows: List<List<String>> = csvReader().readAll(file)
Read with header
val csvData: String = "a,b,c\nd,e,f"
val rows: List<Map<String, String>> = csvReader().readAllWithHeader(csvData)
println(rows) //[{a=d, b=e, c=f}]
Read as Sequence
Sequence type allows to execute lazily. It starts to process each rows before reading all row data.
Learn more about the Sequence type on Kotlin's official documentation.
csvReader().open("test1.csv") {
readAllAsSequence().forEach { row: List<String> ->
//Do something
println(row) //[a, b, c]
}
}
csvReader().open("test2.csv") {
readAllWithHeaderAsSequence().forEach { row: Map<String, String> ->
//Do something
println(row) //{id=1, name=doyaaaaaken}
}
}
NOTE: readAllAsSequence and readAllWithHeaderAsSequence methods can only be called within the open lambda block. The input stream is closed after the open lambda block.
Read line by line
If you want to handle line-by-line, you can do it by using open method. Use open method and then use readNext method inside nested block to read row.
csvReader().open("test.csv") {
readNext()
}
Read in a Suspending Function
csvReader().openAsync("test.csv") {
val container = mutalbeListOf<List<String>>()
delay(100) //other suspending task
readAllAsSequence().asFlow().collect { row ->
delay(100) // other suspending task
container.add(row)
}
}
Note: openAsync can be and only be accessed through a coroutine or another suspending function
Customize
When you create CsvReader, you can choose read options:
// this is tsv reader's option
val tsvReader = csvReader {
charset = "ISO_8859_1"
quoteChar = '"'
delimiter = '\t'
escapeChar = '\\'
}
Option
default value
description
logger
no-op
Logger instance for logging debug information at runtime.
charset
UTF-8
Charset encoding. The value must be supported by java.nio.charset.Charset.
quoteChar
"
Character used to quote fields.
delimiter
,
Character used as delimiter between each field. Use "\t" if reading TSV file.
escapeChar
"
Character to escape quote inside field string. Normally, you don't have to change this option. See detail comment on ICsvReaderContext.
skipEmptyLine
false
Whether to skip or error out on empty lines.
autoRenameDuplicateHeaders
false
Whether to auto rename duplicate headers or throw an exception.
skipMissMatchedRow
false
Deprecated. Replace with appropriate values in excessFieldsRowBehaviour and insufficientFieldsRowBehaviour, e.g. both set to IGNORE. Whether to skip an invalid row. If ignoreExcessCols is true, only rows with less than the expected number of columns will be skipped.
excessFieldsRowBehaviour
ERROR
Behaviour to use when a row has more fields (columns) than expected. ERROR (default), IGNORE (skip the row) or TRIM (remove the excess fields at the end of the row to match the expected number of fields).
insufficientFieldsRowBehaviour
ERROR
Behaviour to use when a row has fewer fields (columns) than expected. ERROR (default), IGNORE (skip the row) or EMPTY_STRING (replace missing fields with an empty string).

CSV Write examples

Simple case
You can start writing csv in one line, no need to do any I/O handling (No need to call use, close and flush method.):
val rows = listOf(listOf("a", "b", "c"), listOf("d", "e", "f"))
csvWriter().writeAll(rows, "test.csv")
// if you'd append data on the tail of the file, assign `append = true`.
csvWriter().writeAll(rows, "test.csv", append = true)
// You can also write into OutpusStream.
csvWriter().writeAll(rows, File("test.csv").outputStream())
You can also write a csv file line by line by open method:
val row1 = listOf("a", "b", "c")
val row2 = listOf("d", "e", "f")
csvWriter().open("test.csv") {
writeRow(row1)
writeRow(row2)
writeRow("g", "h", "i")
writeRows(listOf(row1, row2))
}
Write in a Suspending Function
val rows = listOf(listOf("a", "b", "c"), listOf("d", "e", "f")).asSequence()
csvWriter().openAsync(testFileName) {
delay(100) //other suspending task
rows.asFlow().collect {
delay(100) // other suspending task
writeRow(it)
}
}
Write as String
val rows = listOf(listOf("a", "b", "c"), listOf("d", "e", "f"))
val csvString: String = csvWriter().writeAllAsString(rows) //a,b,c\r\nd,e,f\r\n
long-running write (manual control for file close)
If you want to close a file writer manually for performance reasons (e.g. streaming scenario), you can use openAndGetRawWriter and get a raw CsvFileWriter. DO NOT forget to close the writer!
val row1 = listOf("a", "b", "c")
@OptIn(KotlinCsvExperimental::class)
val writer = csvWriter().openAndGetRawWriter("test.csv")
writer.writeRow(row1)
writer.close()
Customize
When you create a CsvWriter, you can choose write options.
val writer = csvWriter {
charset = "ISO_8859_1"
delimiter = '\t'
nullCode = "NULL"
lineTerminator = "\n"
outputLastLineTerminator = true
quote {
mode = WriteQuoteMode.ALL
char = '\''
}
}
Option
default value
description
charset
UTF-8
Charset encoding. The value must be supported by java.nio.charset.Charset.
delimiter
,
Character used as delimiter between each fields. Use "\t" if reading TSV file.
nullCode
(empty string)
Character used when a written field is null value.
lineTerminator
\r
Character used as line terminator.
outputLastLineTerminator
true
Output line break at the end of file or not.
prependBOM
false
Output BOM (Byte Order Mark) at the beginning of file or not.
quote.char
"
Character to quote each fields.
quote.mode
CANONICAL
Quote mode. - CANONICAL: Not quote normally, but quote special characters (quoteChar, delimiter, line feed). This is the specification of CSV. - ALL: Quote all fields. - NON_NUMERIC: Quote non-numeric fields. (ex. 1,"a",2.3)
Documents
Libraries which use kotlin-csv

Miscellaneous

🤝 Contributing

Contributions, issues and feature requests are welcome! If you have questions, ask away in Kotlin Slack's kotlin-csv room.

💻 Development

git clone [email protected]:doyaaaaaken/kotlin-csv.git
cd kotlin-csv
./gradlew check

Show your support

Give a ⭐️ if this project helped you!

📝 License

Copyright © 2019 doyaaaaaken. This project is licensed under Apache 2.0.

This project is inspired ❤️ by scala-csv
This README was generated with ❤️ by readme-md-generator
Last modified 1mo ago