cache library version (#2238)

pongad · web-flow · commit 793943cbb6c0 · 2017-07-15T12:33:18.000+10:00
so we don't need to read environment properties every call. Fixes #2234. This is not the approach proposed in the issue. As implemented in this PR, we will read the property once for every client instantiation, not once ever. Still, this should be fast enough, and we won't need to maintain double-check-locking mechanism.
diff --git a/google-cloud-core-http/src/main/java/com/google/cloud/http/HttpTransportOptions.java b/google-cloud-core-http/src/main/java/com/google/cloud/http/HttpTransportOptions.java
@@ -149,6 +149,7 @@ public HttpRequestInitializer getHttpRequestInitializer(
     final HttpRequestInitializer delegate =
         scopedCredentials != null && scopedCredentials != NoCredentials.getInstance()
             ? new HttpCredentialsAdapter(scopedCredentials) : null;
+    final String xGoogHeader = getXGoogApiClientHeader(serviceOptions.getLibraryVersion());
     return new HttpRequestInitializer() {
       @Override
       public void initialize(HttpRequest httpRequest) throws IOException {
@@ -163,8 +164,7 @@ public void initialize(HttpRequest httpRequest) throws IOException {
         }
 
         HttpHeaders headers = httpRequest.getHeaders();
-        headers.set(
-            "x-goog-api-client", getXGoogApiClientHeader(serviceOptions.getLibraryVersion()));
+        headers.set("x-goog-api-client", xGoogHeader);
       }
     };
   }

Original file line number	Diff line number	Diff line change
`@@ -149,6 +149,7 @@ public HttpRequestInitializer getHttpRequestInitializer(`
`149`	`149`	`final HttpRequestInitializer delegate =`
`150`	`150`	`scopedCredentials != null && scopedCredentials != NoCredentials.getInstance()`
`151`	`151`	`? new HttpCredentialsAdapter(scopedCredentials) : null;`
	`152`	`+ final String xGoogHeader = getXGoogApiClientHeader(serviceOptions.getLibraryVersion());`
`152`	`153`	`return new HttpRequestInitializer() {`
`153`	`154`	`@Override`
`154`	`155`	`public void initialize(HttpRequest httpRequest) throws IOException {`
`@@ -163,8 +164,7 @@ public void initialize(HttpRequest httpRequest) throws IOException {`
`163`	`164`	`}`
`164`	`165`
`165`	`166`	`HttpHeaders headers = httpRequest.getHeaders();`
`166`		`- headers.set(`
`167`		`- "x-goog-api-client", getXGoogApiClientHeader(serviceOptions.getLibraryVersion()));`
	`167`	`+ headers.set("x-goog-api-client", xGoogHeader);`
`168`	`168`	`}`
`169`	`169`	`};`
`170`	`170`	`}`