142 lines
5.4 KiB
Markdown
142 lines
5.4 KiB
Markdown
[](https://opensource.org/licenses/Apache-2.0)
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[](https://kotlinlang.org/)
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[](https://oss.sonatype.org/content/repositories/snapshots/net/thauvin/erik/urlencoder/)
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[](https://github.com/ethauvin/urlencoder/releases/latest)
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[](https://maven-badges.herokuapp.com/maven-central/net.thauvin.erik/urlencoder)
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[](https://sonarcloud.io/dashboard?id=ethauvin_urlencoder)
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[](https://github.com/ethauvin/urlencoder/actions/workflows/gradle.yml)
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[](https://github.com/ethauvin/urlencoder/actions/workflows/gradle.yml)
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# URL Encoder for Kotlin
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A simple defensive library to encode/decode URL components.
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This library was adapted from the [RIFE2 Web Application Framework](https://rife2.com).
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A pure Java version can also be found at [https://github.com/gbevin/urlencoder](https://github.com/gbevin/urlencoder).
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The rules are determined by combining the unreserved character set from
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[RFC 3986](https://www.rfc-editor.org/rfc/rfc3986#page-13) with the
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percent-encode set from
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[application/x-www-form-urlencoded](https://url.spec.whatwg.org/#application-x-www-form-urlencoded-percent-encode-set).
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Both specs above support percent decoding of two hexadecimal digits to a
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binary octet, however their unreserved set of characters differs and
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`application/x-www-form-urlencoded` adds conversion of space to `+`,
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that has the potential to be misunderstood.
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This class encodes with rules that will be decoded correctly in either case.
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Additionally, this library allocates no memory when encoding isn't needed and
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does the work in a single pass without multiple loops. Both of these
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optimizations have a significantly beneficial impact on performance of encoding
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compared to other solutions like the standard `URLEncoder` in the JDK or
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`UriUtils` in Spring.
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## Examples (TL;DR)
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```kotlin
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UrlEncoder.encode("a test &") // -> a%20test%20%26
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UrlEncoder.encode("%#okékÉȢ smile!😁") // -> %25%23ok%C3%A9k%C3%89%C8%A2%20smile%21%F0%9F%98%81
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UrlEncoder.encode("?test=a test", allow = "?=") // -> ?test=a%20test
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UrlEncoder.endode("foo bar", spaceToPlus = true) // -> foo+bar
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UrlEncoder.decode("a%20test%20%26") // -> a test &
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UrlEncoder.decode("%25%23ok%C3%A9k%C3%89%C8%A2%20smile%21%F0%9F%98%81") // -> %#okékÉȢ smile!😁
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UrlEncoder.decode("foo+bar", plusToSpace = true) // -> foo bar
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```
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## Gradle, Maven, etc.
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To use with [Gradle](https://gradle.org/), include the following dependency in your build file:
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```gradle
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repositories {
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mavenCentral()
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maven { url = uri("https://oss.sonatype.org/content/repositories/snapshots") } // only needed for SNAPSHOT
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}
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dependencies {
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implementation("net.thauvin.erik:urlencoder:1.3.0")
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}
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```
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Instructions for using with Maven, Ivy, etc. can be found
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on [Maven Central](https://maven-badges.herokuapp.com/maven-central/net.thauvin.erik/urlencoder).
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## Standalone usage
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UrlEncoder can be used on the command line also, both for encoding and decoding.
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You have two options:
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* run it with Gradle
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* build the jar and launch it with Java
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The usage is as follows:
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```
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Encode and decode URL components defensively.
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-e encode (default)
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-d decode
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```
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### Running with Gradle
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```shell
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./gradlew run --args="-e 'a test &'" # -> a%20test%20%26
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./gradlew run --args="%#okékÉȢ" # -> %25%23ok%C3%A9k%C3%89%C8%A2
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./gradlew run --args="-d 'a%20test%20%26'" # -> a test &
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```
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### Running with Java
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First build the jar file:
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```shell
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./gradlew clean fatJar
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```
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Then run it:
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```shell
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java -jar lib/build/libs/urlencoder-*all.jar -e "a test &" # -> a%20test%20%26
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java -jar lib/build/libs/urlencoder-*all.jar "%#okékÉȢ" # -> %25%23ok%C3%A9k%C3%89%C8%A2
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java -jar lib/build/libs/urlencoder-*.all.jar -d "a%20test%20%26" # -> a test &
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```
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## Why not simply use `java.net.URLEncoder`?
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Apart for being quite inefficient, some URL components encoded with `URLEncoder.encode` might not be able to be properly decoded.
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For example, a simply search query such as:
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```kotlin
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val u = URLEncoder.encode("foo +bar", StandardCharsets.UTF_8)
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```
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would be encoded as:
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```
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foo+%2Bbar
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```
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Trying to decode it with [Spring](https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/util/UriUtils.html#decode(java.lang.String,java.lang.String)), for example:
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```kotlin
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UriUtils.decode(u, StandardCharsets.UTF_8))
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```
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would return:
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```
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foo++bar
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```
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Unfortunately, decoding with [Uri.decode](https://developer.android.com/reference/android/net/Uri#decode(java.lang.String)) on Android, [decodeURI](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/decodeURI) in Javascript, etc. would yield the exact same result.
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