Change Log

Version 3.0.1

2016-01-14

Rollback OSGi support. This was causing library jars to include more classes than expected, which interfered with Gradle builds.

Version 3.0.0

2016-01-13

This release commits to a stable 3.0 API. Read the 3.0.0-RC1 changes for advice on upgrading from 2.x to 3.x.

The Callback interface now takes a Call. This makes it easier to check if the call was canceled from within the callback. When migrating async calls to this new API, Call is now the first parameter for both onResponse() and onFailure().
Fix: handle multiple cookies in JavaNetCookieJar on Android.
Fix: improve the default HTTP message in MockWebServer responses.
Fix: don't leak file handles when a conditional GET throws.
Fix: Use charset specified by the request body content type in OkHttp's logging interceptor.
Fix: Don't eagerly release pools on cache hits.
New: Make OkHttp OSGi ready.
New: Add already-implemented interfaces Closeable and Flushable to the cache.

Version 3.0.0-RC1

2016-01-02

OkHttp 3 is a major release focused on API simplicity and consistency. The API changes are numerous but most are cosmetic. Applications should be able to upgrade from the 2.x API to the 3.x API mechanically and without risk.

Because the release includes breaking API changes, we're changing the project's package name from com.squareup.okhttp to okhttp3. This should make it possible for large applications to migrate incrementally. The Maven group ID is now com.squareup.okhttp3. For an explanation of this strategy, see Jake Wharton's post, Java Interoperability Policy for Major Version Updates.

This release obsoletes OkHttp 2.x, and all code that uses OkHttp's com.squareup.okhttp package should upgrade to the okhttp3 package. Libraries that depend on OkHttp should upgrade quickly to prevent applications from being stuck on the old version.

There is no longer a global singleton connection pool. In OkHttp 2.x, all OkHttpClient instances shared a common connection pool by default. In OkHttp 3.x, each new OkHttpClient gets its own private connection pool. Applications should avoid creating many connection pools as doing so prevents connection reuse. Each connection pool holds its own set of connections alive so applications that have many pools also risk exhausting memory!

The best practice in OkHttp 3 is to create a single OkHttpClient instance and share it throughout the application. Requests that needs a customized client should call OkHttpClient.newBuilder() on that shared instance. This allows customization without the drawbacks of separate connection pools.
OkHttpClient is now stateless. In the 2.x API OkHttpClient had getters and setters. Internally each request was forced to make its own complete snapshot of the OkHttpClient instance to defend against racy configuration changes. In 3.x, OkHttpClient is now stateless and has a builder. Note that this class is not strictly immutable as it has stateful members like the connection pool and cache.
Get and Set prefixes are now avoided. With ubiquitous builders throughout OkHttp these accessor prefixes aren't necessary. Previously OkHttp used get and set prefixes sporadically which make the API inconsistent and awkward to explore.
OkHttpClient now implements the new Call.Factory interface. This interface will make your code easier to test. When you test code that makes HTTP requests, you can use this interface to replace the real OkHttpClient with your own mocks or fakes.

The interface will also let you use OkHttp's API with another HTTP client's implementation. This is useful in sandboxed environments like Google App Engine.
OkHttp now does cookies. We've replaced java.net.CookieHandler with a new interface, CookieJar and added our own Cookie model class. This new cookie follows the latest RFC and supports the same cookie attributes as modern web browsers.
Form and Multipart bodies are now modeled. We've replaced the opaque FormEncodingBuilder with the more powerful FormBody and FormBody.Builder combo. Similarly we've upgraded MultipartBuilder into MultipartBody, MultipartBody.Part, and MultipartBody.Builder.
The Apache HTTP client and HttpURLConnection APIs are deprecated. They continue to work as they always have, but we're moving everything to the new OkHttp 3 API. The okhttp-apache and okhttp-urlconnection modules should be only be used to accelerate a transition to OkHttp's request/response API. These deprecated modules will be dropped in an upcoming OkHttp 3.x release.
Canceling batches of calls is now the application's responsibility. The API to cancel calls by tag has been removed and replaced with a more general mechanism. The dispatcher now exposes all in-flight calls via its runningCalls() and queuedCalls() methods. You can write code that selects calls by tag, host, or whatever, and invokes Call.cancel() on the ones that are no longer necessary.
OkHttp no longer uses the global java.net.Authenticator by default. We've changed our Authenticator interface to authenticate web and proxy authentication failures through a single method. An adapter for the old authenticator is available in the okhttp-urlconnection module.
Fix: Don't throw IOException on ResponseBody.contentLength() or close().
Fix: Never throw converting an HttpUrl to a java.net.URI. This changes the uri() method to handle malformed percent-escapes and characters forbidden by URI.
Fix: When a connect times out, attempt an alternate route. Previously route selection was less efficient when differentiating failures.
New: Response.peekBody() lets you access the response body without consuming it. This may be handy for interceptors!
New: HttpUrl.newBuilder() resolves a link to a builder.
New: Add the TLS version to the Handshake.
New: Drop Request.uri() and Request#urlString(). Just use Request.url().uri() and Request.url().toString().
New: Add URL to HTTP response logging.
New: Make HttpUrl the blessed URL method of Request.

Version 2.7.2

2016-01-07

Fix: Don't eagerly release stream allocations on cache hits. We might still need them to handle redirects.

Version 2.7.1

2016-01-01

Fix: Don't do a health check on newly-created connections. This is unnecessary work that could put the client in an inconsistent state if the health check fails.

Version 2.7.0

2015-12-13

Rewritten connection management. Previously OkHttp's connection pool managed both idle and active connections for HTTP/2, but only idle connections for HTTP/1.x. With this update the connection pool manages both idle and active connections for everything. OkHttp now detects and warns on connections that were allocated but never released, and will enforce HTTP/2 stream limits. This update also fixes Call.cancel() to not do I/O on the calling thread.
Fix: Don't log gzipped data in the logging interceptor.
Fix: Don't resolve DNS addresses when connecting through a SOCKS proxy.
Fix: Drop the synthetic OkHttp-Selected-Protocol response header.
Fix: Support 204 and 205 'No Content' replies in the logging interceptor.
New: Add Call.isExecuted().

Version 2.6.0

2015-11-22

New Logging Interceptor. The logging-interceptor subproject offers simple request and response logging. It may be configured to log headers and bodies for debugging. It requires this Maven dependency:
```
<dependency>
  <groupId>com.squareup.okhttp</groupId>
  <artifactId>logging-interceptor</artifactId>
  <version>2.6.0</version>
</dependency>
```
Configure basic logging like this:
```
HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BASIC);
client.networkInterceptors().add(loggingInterceptor);
```
Warning: Avoid Level.HEADERS and Level.BODY in production because they could leak passwords and other authentication credentials to insecure logs.
WebSocket API now uses RequestBody and ResponseBody for messages. This is a backwards-incompatible API change.
The DNS service is now pluggable. In some situations this may be useful to manually prioritize specific IP addresses.
Fix: Don't throw when converting an HttpUrl to a java.net.URI. Previously URLs with special characters like | and [ would break when subjected to URI’s overly-strict validation.
Fix: Don't re-encode + as %20 in encoded URL query strings. OkHttp prefers %20 when doing its own encoding, but will retain + when that is provided.
Fix: Enforce that callers call WebSocket.close() on IO errors. Error handling in WebSockets is significantly improved.
Fix: Don't use SPDY/3 style header concatenation for HTTP/2 request headers. This could have corrupted requests where multiple headers had the same name, as in cookies.
Fix: Reject bad characters in the URL hostname. Previously characters like \0 would cause a late crash when building the request.
Fix: Allow interceptors to change the request method.
Fix: Don’t use the request's User-Agent or Proxy-Authorization when connecting to an HTTPS server via an HTTP tunnel. The Proxy-Authorization header was being leaked to the origin server.
Fix: Digits may be used in a URL scheme.
Fix: Improve connection timeout recovery.
Fix: Recover from getsockname crashes impacting Android releases prior to 4.2.2.
Fix: Drop partial support for HTTP/1.0. Previously OkHttp would send HTTP/1.0 on connections after seeing a response with HTTP/1.0. The fixed behavior is consistent with Firefox and Chrome.
Fix: Allow a body in OPTIONS requests.
Fix: Don't percent-encode non-ASCII characters in URL fragments.
Fix: Handle null fragments.
Fix: Don’t crash on interceptors that throw IOException before a connection is attempted.
New: Support WebDAV HTTP methods.
New: Buffer WebSocket frames for better performance.
New: Drop support for TLS_DHE_DSS_WITH_AES_128_CBC_SHA, our only remaining DSS cipher suite. This is consistent with Firefox and Chrome which have also dropped these cipher suite.

Version 2.5.0

2015-08-25

Timeouts now default to 10 seconds. Previously we defaulted to never timing out, and that was a lousy policy. If establishing a connection, reading the next byte from a connection, or writing the next byte to a connection takes more than 10 seconds to complete, you’ll need to adjust the timeouts manually.
OkHttp now rejects request headers that contain invalid characters. This includes potential security problems (newline characters) as well as simple non-ASCII characters (including international characters and emoji).
Call canceling is more reliable. We had a bug where a socket being connected wasn't being closed when the application used Call.cancel().
Changing a HttpUrl’s scheme now tracks the default port. We had a bug where changing a URL from http to https would leave it on port 80.

Okio has been updated to 1.6.0.

<dependency>
  <groupId>com.squareup.okio</groupId>
  <artifactId>okio</artifactId>
  <version>1.6.0</version>
</dependency>

New: Cache.initialize(). Call this on a background thread to eagerly initialize the response cache.
New: Fold MockWebServerRule into MockWebServer. This makes it easier to write JUnit tests with MockWebServer. The MockWebServer library now depends on JUnit, though it continues to work with all testing frameworks.
Fix: FormEncodingBuilder is now consistent with browsers in which characters it escapes. Previously we weren’t percent-encoding commas, parens, and other characters.
Fix: Relax FormEncodingBuilder to support building empty forms.
Fix: Timeouts throw SocketTimeoutException, not InterruptedIOException.
Fix: Change MockWebServer to use the same logic as OkHttp when determining whether an HTTP request permits a body.
Fix: HttpUrl now uses the canonical form for IPv6 addresses.
Fix: Use HttpUrl internally.
Fix: Recover from Android 4.2.2 EBADF crashes.
Fix: Don't crash with an IllegalStateException if an HTTP/2 or SPDY write fails, leaving the connection in an inconsistent state.
Fix: Make sure the default user agent is ASCII.

Version 2.4.0

2015-05-22

Forbid response bodies on HTTP 204 and 205 responses. Webservers that return such malformed responses will now trigger a ProtocolException in the client.
WebSocketListener has incompatible changes. The onOpen() method is now called on the reader thread, so implementations must return before further websocket messages will be delivered. The onFailure() method now includes an HTTP response if one was returned.

Version 2.4.0-RC1

2015-05-16

New HttpUrl API. It's like java.net.URL but good. Note that Request.Builder.url() now throws IllegalArgumentException on malformed URLs. (Previous releases would throw a MalformedURLException when calling a malformed URL.)
We've improved connect failure recovery. We now differentiate between setup, connecting, and connected and implement appropriate recovery rules for each. This changes Address to no longer use ConnectionSpec. (This is an incompatible API change).
FormEncodingBuilder now uses %20 instead of + for encoded spaces. Both are permitted-by-spec, but %20 requires fewer special cases.

Okio has been updated to 1.4.0.

<dependency>
  <groupId>com.squareup.okio</groupId>
  <artifactId>okio</artifactId>
  <version>1.4.0</version>
</dependency>

Request.Builder no longer accepts null if a request body is required. Passing null will now fail for request methods that require a body. Instead use an empty body such as this one:
```
    RequestBody.create(null, new byte[0]);
```

CertificatePinner now supports wildcard hostnames. As always with certificate pinning, you must be very careful to avoid bricking your app. You'll need to pin both the top-level domain and the *. domain for full coverage.

 client.setCertificatePinner(new CertificatePinner.Builder()
     .add("publicobject.com",   "sha1/DmxUShsZuNiqPQsX2Oi9uv2sCnw=")
     .add("*.publicobject.com", "sha1/DmxUShsZuNiqPQsX2Oi9uv2sCnw=")
     .add("publicobject.com",   "sha1/SXxoaOSEzPC6BgGmxAt/EAcsajw=")
     .add("*.publicobject.com", "sha1/SXxoaOSEzPC6BgGmxAt/EAcsajw=")
     .add("publicobject.com",   "sha1/blhOM3W9V/bVQhsWAcLYwPU6n24=")
     .add("*.publicobject.com", "sha1/blhOM3W9V/bVQhsWAcLYwPU6n24=")
     .add("publicobject.com",   "sha1/T5x9IXmcrQ7YuQxXnxoCmeeQ84c=")
     .add("*.publicobject.com", "sha1/T5x9IXmcrQ7YuQxXnxoCmeeQ84c=")
     .build());

Interceptors lists are now deep-copied by OkHttpClient.clone(). Previously clones shared interceptors, which made it difficult to customize the interceptors on a request-by-request basis.
New: Headers.toMultimap().
New: RequestBody.create(MediaType, ByteString).
New: ConnectionSpec.isCompatible(SSLSocket).
New: Dispatcher.getQueuedCallCount() and Dispatcher.getRunningCallCount(). These can be useful in diagnostics.
Fix: OkHttp no longer shares timeouts between pooled connections. This was causing some applications to crash when connections were reused.
Fix: OkApacheClient now allows an empty PUT and POST.
Fix: Websockets no longer rebuffer socket streams.
Fix: Websockets are now better at handling close frames.
Fix: Content type matching is now case insensitive.
Fix: Vary headers are not lost with android.net.http.HttpResponseCache.
Fix: HTTP/2 wasn't enforcing stream timeouts when writing the underlying connection. Now it is.
Fix: Never return null on call.proceed(). This was a bug in call cancelation.
Fix: When a network interceptor mutates a request, that change is now reflected in Response.networkResponse().
Fix: Badly-behaving caches now throw a checked exception instead of a NullPointerException.
Fix: Better handling of uncaught exceptions in MockWebServer with HTTP/2.

Version 2.3.0

2015-03-16

HTTP/2 support. We've done interop testing and haven't seen any problems. HTTP/2 support has been a big effort and we're particularly thankful to Adrian Cole who has helped us to reach this milestone.
RC4 cipher suites are no longer supported by default. To connect to old, obsolete servers relying on these cipher suites, you must create a custom ConnectionSpec.
Beta WebSockets support.. The okhttp-ws subproject offers a new websockets client. Please try it out! When it's ready we intend to include it with the core OkHttp library.

Okio updated to 1.3.0.

<dependency>
  <groupId>com.squareup.okio</groupId>
  <artifactId>okio</artifactId>
  <version>1.3.0</version>
</dependency>

Fix: improve parallelism of async requests. OkHttp's Dispatcher had a misconfigured ExecutorService that limited the number of worker threads. If you're using Call.enqueue() this update should significantly improve request concurrency.
Fix: Lazily initialize the response cache. This avoids strict mode warnings when initializing OkHttp on Android‘s main thread.
Fix: Disable ALPN on Android 4.4. That release of the feature was unstable and prone to native crashes in the underlying OpenSSL code.
Fix: Don't send both If-None-Match and If-Modified-Since cache headers when both are applicable.
Fix: Fail early when a port is out of range.
Fix: Offer Content-Length headers for multipart request bodies.
Fix: Throw UnknownServiceException if a cleartext connection is attempted when explicitly forbidden.
Fix: Throw a SSLPeerUnverifiedException when host verification fails.
Fix: MockWebServer explicitly closes sockets. (On some Android releases, closing the input stream and output stream of a socket is not sufficient.
Fix: Buffer outgoing HTTP/2 frames to limit how many outgoing frames are created.
Fix: Avoid crashing when cache writing fails due to a full disk.
Fix: Improve caching of private responses.
Fix: Update cache-by-default response codes.
Fix: Reused Request.Builder instances no longer hold stale URL fields.
New: ConnectionSpec can now be configured to use the SSL socket's default cipher suites. To use, set the cipher suites to null.
New: Support DELETE with a request body.
New: Headers.of(Map) creates headers from a Map.

Version 2.2.0

2014-12-30

RequestBody.contentLength() now throws IOException. This is a source-incompatible change. If you have code that calls RequestBody.contentLength(), your compile will break with this update. The change is binary-compatible, however: code compiled for OkHttp 2.0 and 2.1 will continue to work with this update.
COMPATIBLE_TLS no longer supports SSLv3. In response to the POODLE vulnerability, OkHttp no longer offers SSLv3 when negotiation an HTTPS connection. If you continue to need to connect to webservers running SSLv3, you must manually configure your own ConnectionSpec.
OkHttp now offers interceptors. Interceptors are a powerful mechanism that can monitor, rewrite, and retry calls. The project wiki has a full introduction to this new API.
New: APIs to iterate and selectively clear the response cache.
New: Support for SOCKS proxies.
New: Support for TLS_FALLBACK_SCSV.
New: Update HTTP/2 support to to h2-16 and hpack-10.
New: APIs to prevent retrying non-idempotent requests.
Fix: Drop NPN support. Going forward we support ALPN only.
Fix: The hostname verifier is now strict. This is consistent with the hostname verifier in modern browsers.
Fix: Improve CONNECT handling for misbehaving HTTP proxies.
Fix: Don't retry requests that failed due to timeouts.
Fix: Cache 302s and 308s that include appropriate response headers.
Fix: Improve pooling of connections that use proxy selectors.
Fix: Don't leak connections when using ALPN on the desktop.
Fix: Update Jetty ALPN to 7.1.2.v20141202 (Java 7) and 8.1.2.v20141202 (Java 8). This fixes a bug in resumed TLS sessions where the wrong protocol could be selected.
Fix: Don't crash in SPDY and HTTP/2 when disconnecting before connecting.
Fix: Avoid a reverse DNS-lookup for a numeric proxy address
Fix: Resurrect http/2 frame logging.
Fix: Limit to 20 authorization attempts.

Version 2.1.0

2014-11-11

New: Typesafe APIs for interacting with cipher suites and TLS versions.
Fix: Don't crash when mixing authorization challenges with upload retries.

Version 2.1.0-RC1

2014-11-04

OkHttp now caches private responses. We've changed from a shared cache to a private cache, and will now store responses that use an Authorization header. This means OkHttp's cache shouldn't be used on middleboxes that sit between user agents and the origin server.
TLS configuration updated. OkHttp now explicitly enables TLSv1.2, TLSv1.1 and TLSv1.0 where they are supported. It will continue to perform only one fallback, to SSLv3. Applications can now configure this with the ConnectionSpec class.

To disable TLS fallback:
```
client.setConnectionSpecs(Arrays.asList(
    ConnectionSpec.MODERN_TLS, ConnectionSpec.CLEARTEXT));
```
To disable cleartext connections, permitting https URLs only:
```
client.setConnectionSpecs(Arrays.asList(
    ConnectionSpec.MODERN_TLS, ConnectionSpec.COMPATIBLE_TLS));
```

New cipher suites. Please confirm that your webservers are reachable with this limited set of cipher suites.

                                         Android
Name                                     Version

TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256  5.0
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256    5.0
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256      5.0
TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA     4.0
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA     4.0
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA       4.0
TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA       4.0
TLS_ECDHE_ECDSA_WITH_RC4_128_SHA         4.0
TLS_ECDHE_RSA_WITH_RC4_128_SHA           4.0
TLS_DHE_RSA_WITH_AES_128_CBC_SHA         2.3
TLS_DHE_DSS_WITH_AES_128_CBC_SHA         2.3
TLS_DHE_RSA_WITH_AES_256_CBC_SHA         2.3
TLS_RSA_WITH_AES_128_GCM_SHA256          5.0
TLS_RSA_WITH_AES_128_CBC_SHA             2.3
TLS_RSA_WITH_AES_256_CBC_SHA             2.3
SSL_RSA_WITH_3DES_EDE_CBC_SHA            2.3  (Deprecated in 5.0)
SSL_RSA_WITH_RC4_128_SHA                 2.3
SSL_RSA_WITH_RC4_128_MD5                 2.3  (Deprecated in 5.0)

Okio updated to 1.0.1.

<dependency>
  <groupId>com.squareup.okio</groupId>
  <artifactId>okio</artifactId>
  <version>1.0.1</version>
</dependency>

New APIs to permit easy certificate pinning. Be warned, certificate pinning is dangerous and could prevent your application from trusting your server!
Cache improvements. This release fixes some severe cache problems including a bug where the cache could be corrupted upon certain access patterns. We also fixed a bug where the cache was being cleared due to a corrupted journal. We've added APIs to configure a request's Cache-Control headers, and to manually clear the cache.
Request cancellation fixes. This update fixes a bug where synchronous requests couldn't be canceled by tag. This update avoids crashing when onResponse() throws an IOException. That failure will now be logged instead of notifying the thread's uncaught exception handler. We've added a new API, Call.isCanceled() to check if a call has been canceled.
New: Update MultipartBuilder to support content length.
New: Make it possible to mock OkHttpClient and Call.
New: Update to h2-14 and hpack-9.
New: OkHttp includes a user-agent by default, like okhttp/2.1.0-RC1.
Fix: Handle response code 308 Permanent Redirect.
Fix: Don't skip the callback if a call is canceled.
Fix: Permit hostnames with underscores.
Fix: Permit overriding the content-type in OkApacheClient.
Fix: Use the socket factory for direct connections.
Fix: Honor OkUrlFactory APIs that disable redirects.
Fix: Don't crash on concurrent modification of SPDY SPDY settings.

Version 2.0.0

This release commits to a stable 2.0 API. Read the 2.0.0-RC1 changes for advice on upgrading from 1.x to 2.x.

2014-06-21

API Change: Use IOException in Callback.onFailure(). This is a source-incompatible change, and is different from OkHttp 2.0.0-RC2 which used Throwable.
Fix: Fixed a caching bug where we weren't storing rewritten request headers like Accept-Encoding.
Fix: Fixed bugs in handling the SPDY window size. This was stalling certain large downloads
Update the language level to Java 7. (OkHttp requires Android 2.3+ or Java 7+.)

Version 2.0.0-RC2

2014-06-11

This update fixes problems in 2.0.0-RC1. Read the 2.0.0-RC1 changes for advice on upgrading from 1.x to 2.x.

Fix: Don't leak connections! There was a regression in 2.0.0-RC1 where connections were neither closed nor pooled.
Fix: Revert builder-style return types from OkHttpClient's timeout methods for binary compatibility with OkHttp 1.x.
Fix: Don't skip client stream 1 on SPDY/3.1. This fixes SPDY connectivity to https://google.com, which doesn't follow the SPDY/3.1 spec!
Fix: Always configure NPN headers. This fixes connectivity to https://facebook.com when SPDY and HTTP/2 are both disabled. Otherwise an unexpected NPN response is received and OkHttp crashes.
Fix: Write continuation frames when HPACK data is larger than 16383 bytes.
Fix: Don't drop uncaught exceptions thrown in async calls.
Fix: Throw an exception eagerly when a request body is not legal. Previously we ignored the problem at request-building time, only to crash later with a NullPointerException.
Fix: Include a backwards-compatible OkHttp-Response-Source header with OkUrlFactory responses.
Fix: Don't include a default User-Agent header in requests made with the Call API. Requests made with OkUrlFactory will continue to have a default user agent.

New: Guava-like API to create headers:

Headers headers = Headers.of(name1, value1, name2, value2, ...).

New: Make the content-type header optional for request bodies.
New: Response.isSuccessful() is a convenient API to check response codes.
New: The response body can now be read outside of the callback. Response bodies must always be closed, otherwise they will leak connections!
New: APIs to create multipart request bodies (MultipartBuilder) and form encoding bodies (FormEncodingBuilder).

Version 2.0.0-RC1

2014-05-23

OkHttp 2 is designed around a new API that is true to HTTP, with classes for requests, responses, headers, and calls. It uses modern Java patterns like immutability and chained builders. The API now offers asynchronous callbacks in addition to synchronous blocking calls.

API Changes

New Request and Response types, each with their own builder. There's also a RequestBody class to write the request body to the network and a ResponseBody to read the response body from the network. The standalone Headers class offers full access to the HTTP headers.
Okio dependency added. OkHttp now depends on Okio, an I/O library that makes it easier to access, store and process data. Using this library internally makes OkHttp faster while consuming less memory. You can write a RequestBody as an Okio BufferedSink and a ResponseBody as an Okio BufferedSource. Standard InputStream and OutputStream access is also available.
New Call and Callback types execute requests and receive their responses. Both types of calls can be canceled via the Call or the OkHttpClient.
URLConnection support has moved to the okhttp-urlconnection module. If you're upgrading from 1.x, this change will impact you. You will need to add the okhttp-urlconnection module to your project and use the OkUrlFactory to create new instances of HttpURLConnection:
```
// OkHttp 1.x:
HttpURLConnection connection = client.open(url);

// OkHttp 2.x:
HttpURLConnection connection = new OkUrlFactory(client).open(url);
```
Custom caches are no longer supported. In OkHttp 1.x it was possible to define your own response cache with the java.net.ResponseCache and OkHttp's OkResponseCache interfaces. Both of these APIs have been dropped. In OkHttp 2 the built-in disk cache is the only supported response cache.
HttpResponseCache has been renamed to Cache. Install it with OkHttpClient.setCache(...) instead of OkHttpClient.setResponseCache(...).
OkAuthenticator has been replaced with Authenticator. This new authenticator has access to the full incoming response and can respond with whichever followup request is appropriate. The Challenge class is now a top-level class and Credential is replaced with a utility class called Credentials.
OkHttpClient.getFollowProtocolRedirects() renamed to getFollowSslRedirects(). We reserve the word protocol for the HTTP version being used (HTTP/1.1, HTTP/2). The old name of this method was misleading; it was always used to configure redirects between https:// and http:// schemes.
RouteDatabase is no longer public API. OkHttp continues to track which routes have failed but this is no exposed in the API.
ResponseSource is gone. This enum exposed whether a response came from the cache, network, or both. OkHttp 2 offers more detail with raw access to the cache and network responses in the new Response class.
TunnelRequest is gone. It specified how to connect to an HTTP proxy. OkHttp 2 uses the new Request class for this.
Dispatcher is a new class that manages the queue of asynchronous calls. It implements limits on total in-flight calls and in-flight calls per host.

Implementation changes

Support Android TrafficStats socket tagging.
Drop authentication headers on redirect.
Added support for compressed data frames.
Process push promise callbacks in order.
Update to http/2 draft 12.
Update to HPACK draft 07.
Add ALPN support. Maven will use ALPN on OpenJDK 8.
Update NPN dependency to target jdk7u60-b13 and Oracle jdk7u55-b13.
Ensure SPDY variants support zero-length DELETE and POST.
Prevent leaking a cache item's InputStreams when metadata read fails.
Use a string to identify TLS versions in routes.
Add frame logger for HTTP/2.
Replacing httpMinorVersion with Protocol. Expose HTTP/1.0 as a potential protocol.
Use Protocol to describe framing.
Implement write timeouts for HTTP/1.1 streams.
Avoid use of SPDY stream ID 1, as that's typically used for UPGRADE.
Support OAuth in Authenticator.
Permit a dangling semicolon in media type parsing.

Version 1.6.0

2014-05-23

Offer bridges to make it easier to migrate from OkHttp 1.x to OkHttp 2.0. This adds OkUrlFactory, Cache, and @Deprecated annotations for APIs dropped in 2.0.

Version 1.5.4

2014-04-14

Drop ALPN support in Android. There's a concurrency bug in all currently-shipping versions.
Support asynchronous disconnects by breaking the socket only. This should prevent flakiness from multiple threads concurrently accessing a stream.

Version 1.5.3

2014-03-29

Fix bug where the Content-Length header was not always dropped when following a redirect from a POST to a GET.
Implement basic support for Thread.interrupt(). OkHttp now checks for an interruption before doing a blocking call. If it is interrupted, it throws an InterruptedIOException.

Version 1.5.2

2014-03-17

Fix bug where deleting a file that was absent from the HttpResponseCache caused an IOException.
Fix bug in HTTP/2 where our HPACK decoder wasn't emitting entries in certain eviction scenarios, leading to dropped response headers.

Version 1.5.1

2014-03-11

Fix 1.5.0 regression where connections should not have been recycled.
Fix 1.5.0 regression where transparent Gzip was broken by attempting to recover from another I/O failure.
Fix problems where spdy/3.1 headers may not have been compressed properly.
Fix problems with spdy/3.1 and http/2 where the wrong window size was being used.
Fix 1.5.0 regression where conditional cache responses could corrupt the connection pool.

Version 1.5.0

2014-03-07

OkHttp no longer uses the default SSL context.

Applications that want to use the global SSL context with OkHttp should configure their OkHttpClient instances with the following:

okHttpClient.setSslSocketFactory(HttpsURLConnection.getDefaultSSLSocketFactory());

A simpler solution is to avoid the shared default SSL socket factory. Instead, if you need to customize SSL, do so for your specific OkHttpClient instance only.

Synthetic headers have changed

Previously OkHttp added a synthetic response header, OkHttp-Selected-Transport. It has been replaced with a new synthetic header, OkHttp-Selected-Protocol.

Changes

New: Support for HTTP-draft-09/2.0.
New: Support for spdy/3.1. Dropped support for spdy/3.
New: Use ALPN on Android platforms that support it (4.4+)
New: CacheControl model and parser.
New: Protocol selection in MockWebServer.
Fix: Route selection shouldn't use TLS modes that we know will fail.
Fix: Cache SPDY responses even if the response body is closed prematurely.
Fix: Use strict timeouts when aborting a download.
Fix: Support Shoutcast HTTP responses like ICY 200 OK.
Fix: Don't unzip if there isn't a response body.
Fix: Don't leak gzip streams on redirects.
Fix: Don't do DNS lookups on invalid hosts.
Fix: Exhaust the underlying stream when reading gzip streams.
Fix: Support the PATCH method.
Fix: Support request bodies on DELETE method.
Fix: Drop the okhttp-protocols module.
Internal: Replaced internal byte array buffers with pooled buffers ("OkBuffer").

Version 1.3.0

2014-01-11

New: Support for "PATCH" HTTP method in client and MockWebServer.
Fix: Drop Content-Length header when redirected from POST to GET.
Fix: Correctly read cached header entries with malformed header names.
Fix: Do not directly support any authentication schemes other than "Basic".
Fix: Respect read timeouts on recycled connections.
Fix: Transmit multiple cookie values as a single header with delimiter.
Fix: Ensure null is never returned from a connection's getHeaderFields().
Fix: Persist proper Content-Encoding header to cache for GZip responses.
Fix: Eliminate rare race condition in SPDY streams that would prevent connection reuse.
Fix: Change HTTP date formats to UTC to conform to RFC2616 section 3.3.
Fix: Support SPDY header blocks with trailing bytes.
Fix: Allow ; as separator for Cache-Control header.
Fix: Correct bug where HTTPS POST requests were always automatically buffered.
Fix: Honor read timeout when parsing SPDY headers.

Version 1.2.1

2013-08-23

Resolve issue with 'jar-with-dependencies' artifact creation.
Fix: Support empty SPDY header values.

Version 1.2.0

2013-08-11

New APIs on OkHttpClient to set default timeouts for connect and read.
Fix bug when caching SPDY responses.
Fix a bug with SPDY plus half-closed streams. (thanks kwuollett)
Fix a bug in Content-Length reporting for gzipped streams in the Apache HTTP client adapter. (thanks kwuollett)
Work around the Alcatel getByInetAddress bug (thanks k.kocel)
Be more aggressive about testing pooled sockets before reuse. (thanks warpspin)
Include Content-Type and Content-Encoding in the Apache HTTP client adapter. (thanks kwuollett)
Add a media type class to OkHttp.

Change custom header prefix:

X-Android-Sent-Millis is now OkHttp-Sent-Millis
X-Android-Received-Millis is now OkHttp-Received-Millis
X-Android-Response-Source is now OkHttp-Response-Source
X-Android-Selected-Transport is now OkHttp-Selected-Transport

Improve cache invalidation for POST-like requests.
Bring MockWebServer into OkHttp and teach it SPDY.

Version 1.1.1

2013-06-23

Fix: ClassCastException when caching responses that were redirected from HTTP to HTTPS.

Version 1.1.0

2013-06-15

Fix: Connection reuse was broken for most HTTPS connections due to a bug in the way the hostname verifier was selected.
Fix: Locking bug in SpdyConnection.
Fix: Ignore null header values (for compatibility with HttpURLConnection).
Add URLStreamHandlerFactory support so that URL.openConnection() uses OkHttp.
Expose the transport ("http/1.1", "spdy/3", etc.) via magic request headers. Use X-Android-Transports to write the preferred transports and X-Android-Selected-Transport to read the negotiated transport.

Version 1.0.2

2013-05-11

Fix: Remove use of Java 6-only APIs.
Fix: Properly handle exceptions from NetworkInterface when querying MTU.
Fix: Ensure MTU has a reasonable default and upper-bound.

Version 1.0.1

2013-05-06

Correct casing of SSL in method names (getSslSocketFactory/setSslSocketFactory).

Version 1.0.0