JarCastingWelcome to kotlin-csv
👋
Pure Kotlin CSV Reader/Writer
Principals
1. Simple interface
- easy to setup
- use DSL so easy to read
2. No need to be aware of file close
- on 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 (Planned in #15)
- kotlin multiplatform project
Usage
Download
gradle DSL:
//gradle kotlin DSL
implementation("com.github.doyaaaaaken:kotlin-csv-jvm:0.15.2")
//gradle groovy DSL
implementation 'com.github.doyaaaaaken:kotlin-csv-jvm:0.15.2'
maven:
<dependency>
<groupId>com.github.doyaaaaaken</groupId>
<artifactId>kotlin-csv-jvm</artifactId>
<version>0.15.2</version>
</dependency>
@file:DependsOn("com.github.doyaaaaaken:kotlin-csv-jvm:0.15.2")
Examples
CSV Read examples
Simple case
You can read csv file from String, java.io.File or java.io.InputStream object.
// 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.
See detail about Sequence type on Kotlin official document.
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 be only called inside open method lambda block. Because, input stream is closed outside open method 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()
}
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)
}
}
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 = '\\'
}
| Opton | default value | description |
|---|---|---|
| charset | UTF-8 |
Charset encoding. The value must be supported by java.nio.charset.Charset. |
| quoteChar | " |
Character used as quote between each fields. |
| delimiter | , |
Character used as delimiter between each fields. 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 |
If empty line is found, skip it or not (=throw an exception). |
| skipMissMatchedRow | false |
If a invalid row which has different number of fields from other rows is found, skip it or not (=throw an exception). |
CSV Write examples
Simple case
You can write csv simply, only one line. No need to call other methods.
Also, You don't have 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 csv file per each line.
Also, You don't have to call use, close and flush 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))
}
long-running write (manual control for file close)
If you want to close file writer manually for performance reason (i.e. streaming scenario), you can use openAndGetRawWriter and get raw CsvFileWriter.
DO NOT forget to call close method manually.
val row1 = listOf("a", "b", "c")
@OptIn(KotlinCsvExperimental::class)
val writer = csvWriter().openAndGetRawWriter("test.csv")
writer.writeRow(row1)
writer.close()
Customize
When you create 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\n |
Character used as line terminator. |
| outputLastLineTerminator | true |
Output line break at the end 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) |
Links
Documents
Libraries which use kotlin-csv
- kotlin-grass: Csv File to Kotlin Data Class Parser.
Miscellaneous
🤝
Contributing
Contributions, issues and feature requests are welcome!
Feel free to check issues page.
If you have question, feel free to ask 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
📝
License
Copyright © 2019 doyaaaaaken.
This project is Apache License 2.0 licensed.
This project is inspired
This README was generated with