HTTPCLIENT-1015: Support only-if-cached directive

Contributed by Michajlo Matijkiw <michajlo_matijkiw at comcast.com>


git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk@1024383 13f79535-47bb-0310-9956-ffa450edef68

httpclient-cache/src/main/java/org/apache/http/impl/client/cache/CachingHttpClient.java

@@ -407,6 +407,11 @@ public class CachingHttpClient implements HttpClient {
                 log.debug("Cache miss [host: " + target + "; uri: " + rl.getUri() + "]");
             }
 
+            if (!mayCallBackend(request)) {
+                return new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_GATEWAY_TIMEOUT,
+                        "Gateway Timeout");
+            }
+
             Set<HttpCacheEntry> variantEntries = null;
             try {
                 responseCache.getVariantCacheEntries(target, request);
@@ -447,6 +452,11 @@ public class CachingHttpClient implements HttpClient {
             return cachedResponse;
         }
 
+        if (!mayCallBackend(request)) {
+            return new BasicHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_GATEWAY_TIMEOUT,
+                    "Gateway Timeout");
+        }
+
         if (validityPolicy.isRevalidatable(entry)) {
             log.debug("Revalidating the cache entry");
 
@@ -472,6 +482,17 @@ public class CachingHttpClient implements HttpClient {
         return callBackend(target, request, context);
     }
 
+    private boolean mayCallBackend(HttpRequest request) {
+        for (Header h: request.getHeaders("Cache-Control")) {
+            for (HeaderElement elt : h.getElements()) {
+                if ("only-if-cached".equals(elt.getName())) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+
     private boolean explicitFreshnessRequest(HttpRequest request, HttpCacheEntry entry, Date now) {
         for(Header h : request.getHeaders("Cache-Control")) {
             for(HeaderElement elt : h.getElements()) {

httpclient-cache/src/test/java/org/apache/http/impl/client/cache/TestCachingHttpClient.java

@@ -1931,6 +1931,59 @@ public class TestCachingHttpClient {
         Assert.assertSame(resp, result);
     }
 
+    @Test
+    public void testIfOnlyIfCachedAndNoCacheEntryBackendNotCalled() throws IOException {
+        impl = new CachingHttpClient(mockBackend);
+
+        request.addHeader("Cache-Control", "only-if-cached");
+
+        HttpResponse resp = impl.execute(host, request);
+
+        Assert.assertEquals(HttpStatus.SC_GATEWAY_TIMEOUT, resp.getStatusLine().getStatusCode());
+    }
+
+    @Test
+    public void testIfOnlyIfCachedAndEntryNotSuitableBackendNotCalled() throws Exception {
+
+        request.setHeader("Cache-Control", "only-if-cached");
+
+        entry = HttpTestUtils.makeCacheEntry(new Header[]{new BasicHeader("Cache-Control", "must-revalidate")});
+
+        requestIsFatallyNonCompliant(null);
+        requestProtocolValidationIsCalled();
+        cacheInvalidatorWasCalled();
+        requestPolicyAllowsCaching(true);
+        getCacheEntryReturns(entry);
+        cacheEntrySuitable(false);
+
+        replayMocks();
+        HttpResponse resp = impl.execute(host, request);
+        verifyMocks();
+
+        Assert.assertEquals(HttpStatus.SC_GATEWAY_TIMEOUT, resp.getStatusLine().getStatusCode());
+    }
+
+    @Test
+    public void testIfOnlyIfCachedAndEntryExistsAndIsSuitableReturnsEntry() throws Exception {
+
+        request.setHeader("Cache-Control", "only-if-cached");
+
+        requestIsFatallyNonCompliant(null);
+        requestProtocolValidationIsCalled();
+        cacheInvalidatorWasCalled();
+        requestPolicyAllowsCaching(true);
+        getCacheEntryReturns(entry);
+        cacheEntrySuitable(true);
+        responseIsGeneratedFromCache();
+        entryHasStaleness(0);
+
+        replayMocks();
+        HttpResponse resp = impl.execute(host, request);
+        verifyMocks();
+
+        Assert.assertSame(mockCachedResponse, resp);
+    }
+
     private void getCacheEntryReturns(HttpCacheEntry result) throws IOException {
         EasyMock.expect(mockCache.getCacheEntry(host, request)).andReturn(result);
     }