gRPC请求中对header进行处理

gRPC请求设置header(Android、iOS、JavaServer)

1.[Android (Java)]

1.1只设置客户端请求时附带的header

见类 io.grpc.stub.MetadataUtils，其中有个方法:

/**
* Attaches a set of request headers to a stub.
*
* @param stub to bind the headers to.
* @param extraHeaders the headers to be passed by each call on the returned stub.
* @return an implementation of the stub with {@code extraHeaders} bound to each call.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1789")
public static <T extends AbstractStub<T>> T attachHeaders(
T stub,
final Metadata extraHeaders) {
return stub.withInterceptors(newAttachHeadersInterceptor(extraHeaders));
}

稍微自己封装一下的效果，如下：

private static <T extends AbstractStub<T>> T attachHeaders(T stub, final Map<String, String> headerMap) {
Metadata extraHeaders = new Metadata();
if (headerMap != null) {
for (String key : headerMap.keySet()) {
Metadata.Key<String> customHeadKey = Metadata.Key.of(key, Metadata.ASCII_STRING_MARSHALLER);
extraHeaders.put(customHeadKey, headerMap.get(key));
}
}
return MetadataUtils.attachHeaders(stub, extraHeaders);
}

1.2 支持设置客户端请求的header以及获取服务端返回结果中的header

第一步：主要是设置http的拦截器ClientInterceptor，拦截器类大概实现代码如下：

/**
* A interceptor to handle client header.
*
* @author Kido
* @email everlastxgb@gmail.com
* @create_time 2016/7/7 11:02
*/

class HeaderClientInterceptor implements ClientInterceptor {

private static final String TAG = "HeaderClientInterceptor";

private Map<String, String> mHeaderMap;

public HeaderClientInterceptor(Map<String, String> headerMap) {
mHeaderMap = headerMap;
}

@Override
public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(MethodDescriptor<ReqT, RespT> method,
CallOptions callOptions, Channel next) {
return new SimpleForwardingClientCall<ReqT, RespT>(next.newCall(method, callOptions)) {

@Override
public void start(Listener<RespT> responseListener, Metadata headers) {
/* put custom header */
if (mHeaderMap != null) {
for (String key : mHeaderMap.keySet()) {
Metadata.Key<String> customHeadKey = Metadata.Key.of(key, Metadata.ASCII_STRING_MARSHALLER);
headers.put(customHeadKey, mHeaderMap.get(key));
}
}
Logger.i(TAG, "header send to server:" + headers);
super.start(new SimpleForwardingClientCallListener<RespT>(responseListener) {
@Override
public void onHeaders(Metadata headers) {
/**
* if you don't need receive header from server,
* you can use {@link io.grpc.stub.MetadataUtils attachHeaders}
* directly to send header
*/
Logger.i(TAG, "header received from server:" + headers);
super.onHeaders(headers);
}
}, headers);
}
};
}
}

第二步：大概使用代码如下：

Map<String, String> headerMap = new HashMap<>();
//...
ClientInterceptor interceptor = new HeaderClientInterceptor(headerMap);
//...
ManagedChannel managedChannel = ManagedChannelBuilder.forAddress(host, port).usePlaintext(true).build();
Channel channel = ClientInterceptors.intercept(managedChannel, interceptor);

// then create stub here by this channel

2. [iOS (Objective-C)]

首先，可以看到GRPCCall中有如下属性：

@property(atomic, readonly) NSDictionary *responseHeaders;
@property(atomic, readonly) NSDictionary *responseTrailers;

接着，可以进行如下设置：

call.requestHeaders[@"My-Header"] = @"Value for this header";
call.requestHeaders[@"Another-Header"] = @"Its value";

3.[Server (Java)]

既然是Java，实现方式应该也和上述Android大概一样。

第一步：拦截器

/**
* A interceptor to handle server header.
*/
public class HeaderServerInterceptor implements ServerInterceptor {

private static final Logger logger = Logger.getLogger(HeaderServerInterceptor.class.getName());

private static Metadata.Key<String> customHeadKey =
Metadata.Key.of("custom_server_header_key", Metadata.ASCII_STRING_MARSHALLER);

@Override
public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
ServerCall<ReqT, RespT> call,
final Metadata requestHeaders,
ServerCallHandler<ReqT, RespT> next) {
logger.info("header received from client:" + requestHeaders);
return next.startCall(new SimpleForwardingServerCall<ReqT, RespT>(call) {
@Override
public void sendHeaders(Metadata responseHeaders) {
responseHeaders.put(customHeadKey, "customRespondValue");
super.sendHeaders(responseHeaders);
}
}, requestHeaders);
}
}

第二步：使用示例

//...
Server server = ServerBuilder.forPort(port)
.addService(ServerInterceptors.intercept(new GreeterImpl(), new HeaderServerInterceptor()))
.build()
.start();
//...