[Java] Fix for issue #3365: Support for gzip compression (#4967)

* Fix for issue 3365 for Java

* Added tests

* Convert CRLF to LF

* Convert CRLF to LF in tests

modules/swagger-codegen/src/main/resources/Java/ApiClient.mustache

@@ -15,6 +15,7 @@ import com.sun.jersey.api.client.Client;
 import com.sun.jersey.api.client.ClientResponse;
 import com.sun.jersey.api.client.GenericType;
 import com.sun.jersey.api.client.config.DefaultClientConfig;
+import com.sun.jersey.api.client.filter.GZIPContentEncodingFilter;
 import com.sun.jersey.api.client.filter.LoggingFilter;
 import com.sun.jersey.api.client.WebResource.Builder;
 
@@ -110,6 +111,7 @@ public class ApiClient {
     DefaultClientConfig conf = new DefaultClientConfig();
     conf.getSingletons().add(jsonProvider);
     Client client = Client.create(conf);
+    client.addFilter(new GZIPContentEncodingFilter({{#useGzipFeature}}true{{/useGzipFeature}}{{^useGzipFeature}}false{{/useGzipFeature}}));
     if (debugging) {
       client.addFilter(new LoggingFilter());
     }

modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache

@@ -128,6 +128,11 @@ public class ApiClient {
     public ApiClient() {
         httpClient = new OkHttpClient();
 
+        {{#useGzipFeature}}
+        // Enable gzip request compression
+        httpClient.interceptors().add(new GzipRequestInterceptor());
+        {{/useGzipFeature}}
+
         verifyingSsl = true;
 
         json = new JSON(this);

modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/GzipRequestInterceptor.mustache

@@ -0,0 +1,70 @@
+{{>licenseInfo}}
+
+package {{invokerPackage}};
+
+import com.squareup.okhttp.*;
+import okio.Buffer;
+import okio.BufferedSink;
+import okio.GzipSink;
+import okio.Okio;
+
+import java.io.IOException;
+
+/**
+ * Encodes request bodies using gzip.
+ *
+ * Taken from https://github.com/square/okhttp/issues/350
+ */
+class GzipRequestInterceptor implements Interceptor {
+    @Override public Response intercept(Chain chain) throws IOException {
+        Request originalRequest = chain.request();
+        if (originalRequest.body() == null || originalRequest.header("Content-Encoding") != null) {
+            return chain.proceed(originalRequest);
+        }
+
+        Request compressedRequest = originalRequest.newBuilder()
+                                                   .header("Content-Encoding", "gzip")
+                                                   .method(originalRequest.method(), forceContentLength(gzip(originalRequest.body())))
+                                                   .build();
+        return chain.proceed(compressedRequest);
+    }
+
+    private RequestBody forceContentLength(final RequestBody requestBody) throws IOException {
+        final Buffer buffer = new Buffer();
+        requestBody.writeTo(buffer);
+        return new RequestBody() {
+            @Override
+            public MediaType contentType() {
+                return requestBody.contentType();
+            }
+
+            @Override
+            public long contentLength() {
+                return buffer.size();
+            }
+
+            @Override
+            public void writeTo(BufferedSink sink) throws IOException {
+                sink.write(buffer.snapshot());
+            }
+        };
+    }
+
+    private RequestBody gzip(final RequestBody body) {
+        return new RequestBody() {
+            @Override public MediaType contentType() {
+                return body.contentType();
+            }
+
+            @Override public long contentLength() {
+                return -1; // We don't know the compressed length in advance!
+            }
+
+            @Override public void writeTo(BufferedSink sink) throws IOException {
+                BufferedSink gzipSink = Okio.buffer(new GzipSink(sink));
+                body.writeTo(gzipSink);
+                gzipSink.close();
+            }
+        };
+    }
+}