fix credentials config

It's always insecure credentials right now.

Author: tadayosi

src/main/java/com/github/tadayosi/tensorflow/serving/client/Configuration.java

@@ -4,6 +4,7 @@
 import java.util.Optional;
 import java.util.Properties;
 
+import io.grpc.ChannelCredentials;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -18,13 +19,14 @@ public class Configuration {
     public static final String CREDENTIALS = "credentials";
 
     private final Optional<String> target;
-    private final Optional<String> credentials;
+    private final Optional<ChannelCredentials> credentials;
 
     private Configuration() {
         Properties props = loadProperties();
 
         this.target = loadProperty(TARGET, props);
-        this.credentials = loadProperty(CREDENTIALS, props);
+        //this.credentials = loadProperty(CREDENTIALS, props);
+        this.credentials = Optional.empty();
     }
 
     static Properties loadProperties() {
@@ -59,7 +61,7 @@ public Optional<String> getTarget() {
         return target;
     }
 
-    public Optional<String> getCredentials() {
+    public Optional<ChannelCredentials> getCredentials() {
         return credentials;
     }
 }

src/main/java/com/github/tadayosi/tensorflow/serving/client/TensorFlowServingClient.java

@@ -41,7 +41,8 @@ public GetModelStatus.GetModelStatusResponse getModelStatus(GetModelStatus.GetMo
     }
 
     @Override
-    public GetModelMetadata.GetModelMetadataResponse getModelMetadata(GetModelMetadata.GetModelMetadataRequest request) {
+    public GetModelMetadata.GetModelMetadataResponse getModelMetadata(
+        GetModelMetadata.GetModelMetadataRequest request) {
         return predictionService.getModelMetadata(request);
     }
 
@@ -65,22 +66,22 @@ public static class Builder {
         private final Configuration configuration = Configuration.load();
 
         private Optional<String> target = configuration.getTarget();
-        private Optional<String> credentials = configuration.getCredentials();
+        private Optional<ChannelCredentials> credentials = configuration.getCredentials();
 
         public Builder target(String target) {
             this.target = Optional.of(target);
             return this;
         }
 
-        public Builder credentials(String credentials) {
+        public Builder credentials(ChannelCredentials credentials) {
             this.credentials = Optional.of(credentials);
             return this;
         }
 
         public TensorFlowServingClient build() {
             return new TensorFlowServingClient(
                 target.orElse(DEFAULT_TARGET),
-                InsecureChannelCredentials.create());
+                credentials.orElse(InsecureChannelCredentials.create()));
         }
     }
 }