OkHttpClientRequest.java

import java.io.IOException;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.List;
import java.util.Map;
import java.util.zip.GZIPOutputStream;

import org.springframework.http.ContentCodingType;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.client.ClientHttpRequest;
import org.springframework.http.client.ClientHttpResponse;

final class OkHttpClientRequest implements ClientHttpRequest {
  private final HttpURLConnection connection;
  private final HttpHeaders headers = new HttpHeaders();

	private boolean executed = false;

	private GZIPOutputStream compressedBody;
	private OutputStream body;

	public OkHttpClientRequest(HttpURLConnection connection) {
		this.connection = connection;
	}

	@Override
	public OutputStream getBody() throws IOException {
		if (this.body == null) {
			writeHeaders(headers);
			this.connection.connect();
			this.body = this.connection.getOutputStream();
		}
		if (shouldCompress()) {
			return getCompressedBody(this.body);
		} else {
			return this.body;
		}
	}

	@Override
	public HttpHeaders getHeaders() {
		return (this.executed ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
	}

	@Override
	public URI getURI() {
		try {
			return this.connection.getURL().toURI();
		} catch (URISyntaxException ex) {
			throw new IllegalStateException("Could not get HttpURLConnection URI: " + ex.getMessage(), ex);
		}
	}

	@Override
	public HttpMethod getMethod() {
		return HttpMethod.valueOf(this.connection.getRequestMethod());
	}

	@Override
	public ClientHttpResponse execute() throws IOException {
		try {
			if (this.body != null) {
				this.body.close();
			} else {
				writeHeaders(headers);
				this.connection.connect();
			}
		} catch (IOException ex) {
			// ignore
		}

		this.executed = true;
		return new OkHttpClientResponse(connection);
	}

	private boolean shouldCompress() {
		List<ContentCodingType> contentCodingTypes = this.headers.getContentEncoding();
		for (ContentCodingType contentCodingType : contentCodingTypes) {
			if (contentCodingType.equals(ContentCodingType.GZIP)) {
				return true;
			}
		}
		return false;
	}

	private OutputStream getCompressedBody(OutputStream body) throws IOException {
		if (this.compressedBody == null) {
			this.compressedBody = new GZIPOutputStream(body);
		}
		return this.compressedBody;
	}

	private void writeHeaders(HttpHeaders headers) {
		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
			String headerName = entry.getKey();
			for (String headerValue : entry.getValue()) {
				this.connection.addRequestProperty(headerName, headerValue);
			}
		}
	}
}

OkHttpClientResponse.java

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.util.List;
import java.util.zip.GZIPInputStream;

import org.springframework.http.ContentCodingType;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.util.StringUtils;

final class OkHttpClientResponse implements ClientHttpResponse {
  private final HttpURLConnection connection;
  private static final String AUTH_ERROR = "Received authentication challenge is null";
	private static final String AUTH_ERROR_JELLY_BEAN = "No authentication challenges found";
	private static final String PROXY_AUTH_ERROR = "Received HTTP_PROXY_AUTH (407) code while not using proxy";
	private HttpHeaders headers;
	private GZIPInputStream compressedBody;

	public OkHttpClientResponse(HttpURLConnection connection) {
		this.connection = connection;
	}

	private int handleIOException(IOException ex) throws IOException {
		if (AUTH_ERROR.equals(ex.getMessage()) || AUTH_ERROR_JELLY_BEAN.equals(ex.getMessage())) {
			return HttpStatus.UNAUTHORIZED.value();
		} else if (PROXY_AUTH_ERROR.equals(ex.getMessage())) {
			return HttpStatus.PROXY_AUTHENTICATION_REQUIRED.value();
		} else {
			throw ex;
		}
	}

	@Override
	public InputStream getBody() throws IOException {
		InputStream errorStream = this.connection.getErrorStream();
		InputStream body = (errorStream != null ? errorStream : this.connection.getInputStream());

		if (isCompressed()) {
			return getCompressedBody(body);
		}
		return body;
	}

	@Override
	public HttpHeaders getHeaders() {
		if (this.headers == null) {
			this.headers = new HttpHeaders();
			// Header field 0 is the status line for most HttpURLConnections, but not on GAE
			String name = this.connection.getHeaderFieldKey(0);
			if (StringUtils.hasLength(name)) {
				this.headers.add(name, this.connection.getHeaderField(0));
			}
			int i = 1;
			while (true) {
				name = this.connection.getHeaderFieldKey(i);
				if (!StringUtils.hasLength(name)) {
					break;
				}
				this.headers.add(name, this.connection.getHeaderField(i));
				i++;
			}
		}
		return this.headers;
	}

	@Override
	public int getRawStatusCode() throws IOException {
		try {
			return this.connection.getResponseCode();
		} catch (IOException ex) {
			return handleIOException(ex);
		}
	}

	@Override
	public HttpStatus getStatusCode() throws IOException {
		return HttpStatus.valueOf(getRawStatusCode());
	}

	@Override
	public String getStatusText() throws IOException {
		try {
			return this.connection.getResponseMessage();
		} catch (IOException ex) {
			return HttpStatus.valueOf(handleIOException(ex)).getReasonPhrase();
		}
	}

	@Override
	public void close() {
		if (this.compressedBody != null) {
			try {
				this.compressedBody.close();
			} catch (IOException e) {
				// ignore
			}
		}
		this.connection.disconnect();
	}

	private boolean isCompressed() {
		List<ContentCodingType> contentCodingTypes = this.getHeaders().getContentEncoding();
		for (ContentCodingType contentCodingType : contentCodingTypes) {
			if (contentCodingType.equals(ContentCodingType.GZIP)) {
				return true;
			}
		}
		return false;
	}

	private InputStream getCompressedBody(InputStream body) throws IOException {
		if (this.compressedBody == null) {
			this.compressedBody = new GZIPInputStream(body);
		}
		return this.compressedBody;
	}
}

OkHttpFactory.java

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.Proxy;
import java.net.URI;

import org.springframework.http.HttpMethod;
import org.springframework.http.client.ClientHttpRequest;
import org.springframework.http.client.ClientHttpRequestFactory;

import com.squareup.okhttp.OkHttpClient;

public class OkHttpFactory implements ClientHttpRequestFactory {

  private final OkHttpClient client = new OkHttpClient();
  private int connectTimeout = -1;
	private int readTimeout = -1;

	@Override
	public ClientHttpRequest createRequest(final URI uri, final HttpMethod httpMethod) throws IOException {
		final HttpURLConnection connection = this.client.open(uri.toURL());
		prepareConnection(connection, httpMethod.name());

		return new OkHttpClientRequest(connection);
	}

	public void setProxy(Proxy proxy) {
		this.client.setProxy(proxy);
	}

	public void setConnectTimeout(int connectTimeout) {
		this.connectTimeout = connectTimeout;
	}

	public void setReadTimeout(int readTimeout) {
		this.readTimeout = readTimeout;
	}

	protected void prepareConnection(HttpURLConnection connection, String httpMethod) throws IOException {
		if (this.connectTimeout >= 0) {
			connection.setConnectTimeout(this.connectTimeout);
		}
		if (this.readTimeout >= 0) {
			connection.setReadTimeout(this.readTimeout);
		}
		connection.setDoInput(true);
		if ("GET".equals(httpMethod)) {
			connection.setInstanceFollowRedirects(true);
		} else {
			connection.setInstanceFollowRedirects(false);
		}
		if ("PUT".equals(httpMethod) || "POST".equals(httpMethod)) {
			connection.setDoOutput(true);
		} else {
			connection.setDoOutput(false);
		}
		connection.setRequestMethod(httpMethod);
	}
}