doc: initiate some package javadoc

Initated package javadoc for 
* `io.grpc.stub`, 
* `io.grpc.auth`, 
* `io.grpc.util`, 
* `io.grpc.protobuf`, 
* `io.grpc.protobuf.lite`,
* `io.grpc.protobuf.nano`

1 files changed, 75 insertions, 0 deletions

diff --git a/stub/src/main/java/io/grpc/stub/package-info.java b/stub/src/main/java/io/grpc/stub/package-info.java
new file mode 100644
index 000000000..6347f1238
--- /dev/null
+++ b/stub/src/main/java/io/grpc/stub/package-info.java
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2017, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *
+ *    * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * API for the Stub layer.
+ *
+ * <p>The gRPC Java API is split into two main parts: The stub layer and the call layer. The stub
+ * layer is a wrapper around the call layer.
+ *
+ * <p>In the most common case of gRPC over Protocol Buffers, stub classes are automatically
+ * generated from service definition .proto files by the Protobuf compiler. See <a
+ * href="http://www.grpc.io/docs/generatedcode/java.html">gRPC java Generated Code Guide</a>.
+ *
+ * <p>The server side stub classes are abstract classes with RPC methods for the server application
+ * to implement/override. These classes internally use {@link io.grpc.stub.ServerCalls} to interact
+ * with the call layer. The RPC methods consume a {@link io.grpc.stub.StreamObserver} object {@code
+ * responseObserver} as one of its arguments. When users are implementing/override these
+ * methods in the server application, they may call the {@link io.grpc.stub.StreamObserver#onNext
+ * onNext()}, {@link io.grpc.stub.StreamObserver#onError onError()} and {@link
+ * io.grpc.stub.StreamObserver#onCompleted onCompleted()} methods on the {@code responseObserver}
+ * argument to send out a response message, error and completion notification respectively. If the
+ * RPC is client-streaming or bidirectional-streaming, the abstract RPC method should return a
+ * {@code requestObserver} which is also a {@link io.grpc.stub.StreamObserver} object. User should
+ * typically implement the {@link io.grpc.stub.StreamObserver#onNext onNext()}, {@link
+ * io.grpc.stub.StreamObserver#onError onError()} and {@link io.grpc.stub.StreamObserver#onCompleted
+ * onCompleted()} callbacks of {@code requestObserver} to define how the server application would
+ * react when receiving a message, error and completion notification respectively from the client
+ * side.
+ *
+ * <p>The client side stub classes are implementations of {@link io.grpc.stub.AbstractStub} that
+ * provide the RPC methods for the client application to call. The RPC methods in the client stubs
+ * internally use {@link io.grpc.stub.ClientCalls} to interact with the call layer. For asynchronous
+ * stubs, the RPC methods also consume a {@link io.grpc.stub.StreamObserver} object {@code
+ * responseObserver} as one of its arguments, and moreover for client-streaming or
+ * bidirectional-streaming, also return a {@code requestObserver} which is also a {@link
+ * io.grpc.stub.StreamObserver} object. In contrast to the server side, users should implement the
+ * {@link io.grpc.stub.StreamObserver#onNext onNext()}, {@link io.grpc.stub.StreamObserver#onError
+ * onError()} and {@link io.grpc.stub.StreamObserver#onCompleted onCompleted()} callbacks of {@code
+ * responseObserver} to define what the client application would do when receiving a response
+ * message, error and completion notification respectively from the server side, and then pass the
+ * {@code responseObserver} to the RPC method in the client stub. If the RPC method returns a {@code
+ * requestObserver}, users should call the {@link io.grpc.stub.StreamObserver#onNext onNext()},
+ * {@link io.grpc.stub.StreamObserver#onError onError()} and {@link
+ * io.grpc.stub.StreamObserver#onCompleted onCompleted()} methods on the {@code requestObserver} to
+ * send out a request message, error and completion notification respectively.
+ */
+package io.grpc.stub;