**This release upgrades OkHttp to Kotlin.** We tried our best to make fast and safe to upgrade
from OkHttp 3.x. We wrote an [upgrade guide][upgrading_to_okhttp_4] to help with the migration and a
[blog post][okhttp4_blog_post] to explain it.

 *  Fix: Target Java 8 bytecode for Java and Kotlin.


## Version 4.0.0-RC3

_2019-06-24_

 *  Fix: Retain binary-compatibility in `okhttp3.internal.HttpMethod`. Naughty third party SDKs

      return new MockResponse()
          .setStatus("HTTP/1.1 404")
          .addHeader("content-type: text/plain; charset=utf-8")
          .setBody("NOT FOUND: " + path);
    } catch (IOException e) {
      return new MockResponse()
          .setStatus("HTTP/1.1 500")
          .addHeader("content-type: text/plain; charset=utf-8")
          .setBody("SERVER ERROR: " + e);
    }
  }

    request.addHeader("Accept", "text/plain")

    httpClient.execute(request).use { response ->
      assertThat(response.code).isEqualTo(200)
      assertThat(EntityUtils.toString(response.entity)).isEqualTo("hello, Apache HttpClient 5.x")
    }

    val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")

       *
       * Example:
       * ```
       * --> POST /greeting http/1.1
       * Host: example.com
       * Content-Type: plain/text
       * Content-Length: 3
       * --> END POST
       *
       * <-- 200 OK (22ms)
       * Content-Type: plain/text
       * Content-Length: 6
       * <-- END HTTP
       * ```
       */
      HEADERS,

      /**

        .header("Accept", "text/plain")
        .build()

    val response = httpClient.send(request, BodyHandlers.ofString())
    assertThat(response.statusCode()).isEqualTo(200)
    assertThat(response.body()).isEqualTo("hello, Java HTTP Client")

    val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")

      assertThat(requestBody.contentType()).isNull()
    }
  }

  @Test
  fun testFileDescriptorMediaType() {
    assertOnFileDescriptor { fd ->
      val contentType = "text/plain".toMediaType()

      val requestBody = fd.toRequestBody(contentType)

      assertThat(requestBody.contentType()).isEqualTo(contentType)
    }
  }

  @Test
  fun testFileDescriptorReadTwice() {

    body.byteStream().close()
    assertThat(closed.get()).isTrue()
  }

  @Test
  fun unicodeTextWithUnsupportedEncoding() {
    val text = "eile oli oliiviõli"
    val body = text.toResponseBody("text/plain; charset=unknown".toMediaType())
    assertThat(body.string()).isEqualTo(text)
  }

  companion object {
    @JvmOverloads
    fun body(
      hex: String,
      charset: String? = null,

  fun getContentTypeConnects() {
    server.enqueue(
      MockResponse(
        headers = headersOf("Content-Type", "text/plain"),
        body = "ABC",
      ),
    )
    val response = getResponse(newRequest("/"))
    assertThat(response.body.contentType()).isEqualTo(
      "text/plain".toMediaType(),
    )
    response.body.close()
  }

  @Test
  fun getContentEncodingConnects() {

    val mediaType = parse("text/plain; charset=\"!@#$%^&*()\"")
    assertNull(mediaType.charsetName())
  }

  @Test fun testUnsupportedCharset() {
    val mediaType = parse("text/plain; charset=utf-wtf")
    assertNull(mediaType.charsetName())
  }

  @Test fun testCharsetNameIsDoubleQuotedAndSingleQuoted() {
    val mediaType = parse("text/plain;charset=\"'utf-8'\"")
    assertNull(mediaType.charsetName())

            .header("Content-Type", "text/plain-ish")
            .build(),
        )
      }
    server.enqueue(MockResponse())
    client.newCall(
      request()
        .post("Hi?".toRequestBody(PLAIN))
        .build(),
    ).execute()
    applicationLogs
      .assertLogEqual("--> POST $url")
      .assertLogEqual("Content-Type: text/plain; charset=utf-8")
      .assertLogEqual("Content-Length: 3")