我正在尝试使用 Google Cloud Speech api 来识别语音，遵循示例代码
https://github.com/GoogleCloudPlatform/java-docs-samples/tree/master/speech/grpc
我已按照说明创建了此处提到的凭据（服务帐户密钥），还创建了计费帐户。
当我执行mvn clean install命令时，它开始运行测试用例；我收到以下错误：
> Running com.examples.cloud.speech.RecognitionAudioFactoryTest
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.652 sec - in com.examples.cloud.speech.RecognitionAudioFactory
Running com.examples.cloud.speech.StreamingRecognizeClientTest
Dec 01, 2016 11:50:07 PM io.grpc.internal.ManagedChannelImpl <init>
INFO: [ManagedChannelImpl@77b5c3de] Created with target speech.googleapis.com:443
WARN - recognize failed: {0}
io.grpc.StatusRuntimeException: UNAUTHENTICATED
at io.grpc.Status.asRuntimeException(Status.java:545)
at io.grpc.stub.ClientCalls$StreamObserverToCallListenerAdapter.onClose(ClientCalls.java:395)
at io.grpc.ClientInterceptors$CheckedForwardingClientCall.start(ClientInterceptors.java:203)
at io.grpc.stub.ClientCalls.startCall(ClientCalls.java:273)
at io.grpc.stub.ClientCalls.asyncStreamingRequestCall(ClientCalls.java:266)
at io.grpc.stub.ClientCalls.asyncBidiStreamingCall(ClientCalls.java:109)
at com.google.cloud.speech.v1beta1.SpeechGrpc$SpeechStub.streamingRecognize(SpeechGrpc.java:206)
at com.examples.cloud.speech.StreamingRecognizeClient.recognize(StreamingRecognizeClient.java:135)
at com.examples.cloud.speech.StreamingRecognizeClientTest.test16KHzAudio(StreamingRecognizeClientTest.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:367)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:274)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:238)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:161)
at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:290)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:242)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:121)
Caused by: java.io.IOException: Error getting access token for service account:
at com.google.auth.oauth2.ServiceAccountCredentials.refreshAccessToken(ServiceAccountCredentials.java:319)
at com.google.auth.oauth2.OAuth2Credentials.refresh(OAuth2Credentials.java:149)
at com.google.auth.oauth2.OAuth2Credentials.getRequestMetadata(OAuth2Credentials.java:135)
at io.grpc.auth.ClientAuthInterceptor.getRequestMetadata(ClientAuthInterceptor.java:150)
at io.grpc.auth.ClientAuthInterceptor.access$100(ClientAuthInterceptor.java:64)
at io.grpc.auth.ClientAuthInterceptor$1.checkedStart(ClientAuthInterceptor.java:96)
at io.grpc.ClientInterceptors$CheckedForwardingClientCall.start(ClientInterceptors.java:195)
... 32 more
Caused by: java.net.UnknownHostException: accounts.google.com
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:625)
at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:432)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:527)
at sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:275)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:371)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.jav
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:933)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177)
at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(HttpURLConnection.java:1092)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:250)
at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:77)
at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:965)
at com.google.auth.oauth2.ServiceAccountCredentials.refreshAccessToken(ServiceAccountCredentials.java:317)
... 38 more
你能帮我理解发生了什么吗？