[components] Issue https://github.com/mozilla-mobile/android-components/issues/1325: (lib-fetch-httpurlconnection): A concept-fetch implementation using HttpURLConnection.

mobile/android/android-components/components/lib/fetch-httpurlconnection/README.md

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+# [Android Components](../../../README.md) > Libraries > Fetch-HttpURLConnection
+
+A [concept-fetch](../../concept/fetch/README.md) implementation using [HttpURLConnection](https://developer.android.com/reference/java/net/HttpURLConnection.html).
+
+This implementation of `concept-fetch` uses [HttpURLConnection](https://developer.android.com/reference/java/net/HttpURLConnection.html) from the standard library of the Android System. Therefore this component has no third-party dependencies and is smaller than other implementations. It's intended use is for apps that have strict APK size constraints.
+
+## Usage
+
+### Setting up the dependency
+
+Use Gradle to download the library from [maven.mozilla.org](https://maven.mozilla.org/) ([Setup repository](../../../README.md#maven-repository)):
+
+```Groovy
+implementation "org.mozilla.components:lib-fetch-httpurlconnection:{latest-version}"
+```
+
+### Performing requests
+
+See the [concept-fetch documentation](../../concept/fetch/README.md) for generic examples of using the API of components implementing `concept-fetch`.
+
+## License
+
+    This Source Code Form is subject to the terms of the Mozilla Public
+    License, v. 2.0. If a copy of the MPL was not distributed with this
+    file, You can obtain one at http://mozilla.org/MPL/2.0/

mobile/android/android-components/components/lib/fetch-httpurlconnection/build.gradle

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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+
+android {
+    compileSdkVersion Config.compileSdkVersion
+
+    defaultConfig {
+        minSdkVersion Config.minSdkVersion
+        targetSdkVersion Config.targetSdkVersion
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation Deps.kotlin_stdlib
+    implementation Deps.kotlin_coroutines
+
+    implementation project(':concept-fetch')
+
+    testImplementation Deps.testing_junit
+    testImplementation Deps.testing_robolectric
+    testImplementation Deps.testing_mockito
+
+    testImplementation project(':tooling-fetch-tests')
+}
+
+apply from: '../../../publish.gradle'
+ext.configurePublish(Config.componentsGroupId, archivesBaseName, gradle.componentDescriptions[archivesBaseName])

mobile/android/android-components/components/lib/fetch-httpurlconnection/proguard-rules.pro

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+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

mobile/android/android-components/components/lib/fetch-httpurlconnection/src/main/AndroidManifest.xml

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+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="mozilla.components.lib.fetch.httpurlconnection" />

mobile/android/android-components/components/lib/fetch-httpurlconnection/src/main/java/mozilla/components/lib/fetch/httpurlconnection/HttpURLConnectionClient.kt

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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.lib.fetch.httpurlconnection
+
+import mozilla.components.concept.fetch.Client
+import mozilla.components.concept.fetch.Headers
+import mozilla.components.concept.fetch.MutableHeaders
+import mozilla.components.concept.fetch.Request
+import mozilla.components.concept.fetch.Response
+import java.io.FileNotFoundException
+import java.io.IOException
+import java.io.InputStream
+import java.net.HttpURLConnection
+import java.net.URL
+import java.util.zip.GZIPInputStream
+
+/**
+ * [HttpURLConnection] implementation of [Client].
+ */
+class HttpURLConnectionClient : Client() {
+    @Throws(IOException::class)
+    override fun fetch(request: Request): Response {
+        val connection = (URL(request.url).openConnection() as HttpURLConnection)
+
+        connection.setupWith(request)
+        connection.addHeadersFrom(request, defaultHeaders = defaultHeaders)
+        connection.addBodyFrom(request)
+
+        return connection.toResponse()
+    }
+}
+
+private fun HttpURLConnection.addBodyFrom(request: Request) {
+    if (request.body == null) {
+        return
+    }
+
+    request.body?.let { body ->
+        doOutput = true
+
+        body.useStream { inStream ->
+            outputStream.use { outStream ->
+                inStream
+                    .buffered()
+                    .copyTo(outStream)
+                outStream.flush()
+            }
+        }
+    }
+}
+
+private fun HttpURLConnection.setupWith(request: Request) {
+    requestMethod = request.method.name
+    instanceFollowRedirects = request.redirect == Request.Redirect.FOLLOW
+
+    request.connectTimeout?.let { (timeout, unit) ->
+        connectTimeout = unit.toMillis(timeout).toInt()
+    }
+
+    request.readTimeout?.let { (timeout, unit) ->
+        readTimeout = unit.toMillis(timeout).toInt()
+    }
+}
+
+private fun HttpURLConnection.addHeadersFrom(request: Request, defaultHeaders: Headers) {
+    defaultHeaders.filter { header ->
+        request.headers?.contains(header.name) != true
+    }.forEach { header ->
+        setRequestProperty(header.name, header.value)
+    }
+
+    request.headers?.forEach { header ->
+        addRequestProperty(header.name, header.value)
+    }
+}
+
+private fun HttpURLConnection.toResponse(): Response {
+    return Response(
+        url.toString(),
+        responseCode,
+        translateHeaders(this),
+        createBody(this)
+    )
+}
+
+private fun translateHeaders(connection: HttpURLConnection): Headers {
+    val headers = MutableHeaders()
+
+    var index = 0
+
+    while (connection.getHeaderField(index) != null) {
+        val name = connection.getHeaderFieldKey(index)
+        if (name == null) {
+            index++
+            continue
+        }
+
+        val value = connection.getHeaderField(index)
+
+        headers.append(name, value)
+
+        index++
+    }
+
+    return headers
+}
+
+private fun createBody(connection: HttpURLConnection): Response.Body {
+    val gzipped = connection.contentEncoding == "gzip"
+
+    withFileNotFoundExceptionIgnored {
+        return HttpUrlConnectionBody(
+            connection,
+            connection.inputStream,
+            gzipped
+        )
+    }
+
+    withFileNotFoundExceptionIgnored {
+        return HttpUrlConnectionBody(
+            connection,
+            connection.errorStream,
+            gzipped
+        )
+    }
+
+    return EmptyBody()
+}
+
+private class EmptyBody : Response.Body("".byteInputStream())
+
+private class HttpUrlConnectionBody(
+    private val connection: HttpURLConnection,
+    stream: InputStream,
+    gzipped: Boolean
+) : Response.Body(if (gzipped) GZIPInputStream(stream) else stream) {
+    override fun close() {
+        super.close()
+
+        connection.disconnect()
+    }
+}
+
+private inline fun withFileNotFoundExceptionIgnored(block: () -> Unit) {
+    try {
+        block()
+    } catch (e: FileNotFoundException) {
+        // Ignore
+    }
+}

mobile/android/android-components/components/lib/fetch-httpurlconnection/src/test/java/mozilla/components/lib/fetch/httpurlconnection/HttpUrlConnectionFetchTestCases.kt

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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package mozilla.components.lib.fetch.httpurlconnection
+
+import mozilla.components.concept.fetch.Client
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class HttpUrlConnectionFetchTestCases : mozilla.components.tooling.fetch.tests.FetchTestCases() {
+    override fun createNewClient(): Client = HttpURLConnectionClient()
+
+    // Inherits test methods from generic test suite base class
+
+    @Test
+    fun `Client instance`() {
+        // We need at least one test case defined here so that this is recognized as test class.
+        assertTrue(createNewClient() is HttpURLConnectionClient)
+    }
+}