使用；框架进行通信时，有时候需要对编写拦截器对请求或者响应对象进行拦截。如何实现拦截呢？
服务端
服务端拦截器如下图所示：
serverCall：是响应的回调接口，可以用于直接关闭请求；
一般拦截器返回的是next.startCall(serverCall, headers);但是如果想获取到请求对象或者响应对象，需要通过装饰器模式来进行增强，在增强的时候，可以做一些处理。
public class TestServerInterceptor implements ServerInterceptor {
public static final Metadata.Key<Long> USER_ID_KEY = Metadata.Key.of("userId", ASCII_LONG_MARSHALLER);
public static final Metadata.Key<String> OPT_NAME_KEY = Metadata.Key.of("userName", ASCII_STRING_MARSHALLER);
public static final ThreadLocal<Long> USER_THREAD_LOCAL = new ThreadLocal<>();
@Override
public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> serverCall, Metadata headers,
ServerCallHandler<ReqT, RespT> next) {
/**
* 处理请求的header，做一些特殊处理
*/
//例如验证权限
if (headers.get(USER_ID_KEY) == null) {
//直接关闭请求
serverCall.close(Status.UNAUTHENTICATED.withDescription("auth failed"), new Metadata());
}
//此处可以将header的值放入到ThreadLocal中
return new ForwardingServerCallListener.SimpleForwardingServerCallListener<ReqT>(next.startCall(
/**
* 回调监听接口
*/
new ForwardingServerCall.SimpleForwardingServerCall<ReqT, RespT>(serverCall) {
/**
* 发送响应报文时候的拦截（可以打印响应报文）
* @param message response message.
*/
@Override
public void sendMessage(RespT message) {
//可以做点什么（这里可以拿到接口的response）
log.info("test open sendMessage：{}", ObjectMapperUtils.toJSON(message));
super.sendMessage(message);
log.info("test close sendMessage");
}
/**
* 发送响应报文的拦截（可以设置响应header头）
* @param headers metadata to send prior to any response body.
*/
@Override
public void sendHeaders(Metadata headers) {
log.info("test open sendHeaders");
Metadata.Key<Long> respXxx = Metadata.Key.of("respXxx", ASCII_LONG_MARSHALLER);
headers.put(respXxx, 1232L);
super.sendHeaders(headers);
log.info("test close sendHeaders");
}
}, headers)) {
/**
* 打印请求报文
*/
@Override
public void onMessage(ReqT message) {
//打印入参
log.info("test open onMessage：{}", ObjectMapperUtils.toJSON(message));
//参数处理，校验，若发现数据有误，则抛出异常
log.info("test close onMessage");
}
/**
* 代表本次请求正常结束
*/
@Override
public void onComplete() {
log.info("test open onComplete()");
//可以做点什么
delegate().onComplete();
log.info("test close onComplete()");
}
/**
* 代表本次请求被取消掉，通常发生在服务端执行出现异常的情况会被调用。
*
* 例如请求超时，会执行到这个方法。
*/
@Override
public void onCancel() {
log.info("test open onCancel()");
delegate().onCancel();
log.info("test close onCancel()");
}
/**
* 贯穿整个请求的整个生命周期。
*/
@Override
public void onHalfClose() {
log.info("test open onHalfClose()");
log.info("test close onHalfClose()");
}
};
//return next.startCall(serverCall, headers);
}
}
执行的顺序：
open onMessage()
close onMessage()
open onHalfClose()
open 业务代码
open onComplete()
close onComplete()
close onHalfClose()
客户端
- SimpleForwardingClientCallListener是对响应报文的监听；
public class TestClientInterceptor implements ClientInterceptor {
public static final Key<Long> USER_ID_KEY = Key.of("userId", ASCII_LONG_MARSHALLER);
public static final Key<String> OPT_NAME_KEY = Key.of("userName", ASCII_STRING_MARSHALLER);
@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) {
/**
* 发送请求报文的时候，对请求的heade进行处理。
*/
log.info("test open injectHeadersFromScope()");
headers.put(USER_ID_KEY, 1001L);
log.info("test close injectHeadersFromScope()");
//开始请求，入参即为响应报文的处理，
super.start(new ForwardingClientCallListener.SimpleForwardingClientCallListener<RespT>(responseListener) {
/**
* 响应报文来了，进行处理
* @param message returned by the server
*/
public void onMessage(RespT message) {
log.info("test open onMessage：{}", ObjectMapperUtils.toJSON(message));
super.onMessage(message);
log.info("test close onMessage ");
}
/**
* 响应报文来了，获取到响应的header头信息
* @param headers containing metadata sent by the server at the start of the response.
*/
@Override
public void onHeaders(Metadata headers) {
Key<Long> respXxx = Key.of("respXxx", ASCII_LONG_MARSHALLER);
log.info("test open onHeaders：{}", headers.get(respXxx));
super.onHeaders(headers);
log.info("test close onHeaders");
}
/**
*
* @param status the result of the remote call. 错误码
* @param trailers metadata provided at call completion.
*/
@Override
public void onClose(Status status, Metadata trailers) {
log.info("test open onClose() :resp {}", ObjectMapperUtils.toJSON(status));
super.onClose(status, trailers);
log.info("test close onClose()");
}
@Override
public void onReady() {
log.info("test open onReady()");
super.onReady();
log.info("test close onReady()");
}
}, headers);
log.info("test close start()");
}
/**
* 发送请求报文
* @param message message to be sent to the server.
*/
@Override
public void sendMessage(ReqT message) {
log.info("test open sendMessage():{}",ObjectMapperUtils.toJSON(message));
super.sendMessage(message);
log.info("test close sendMessage()");
}
@Override
public void halfClose() {
log.info("test open halfClose()");
super.halfClose();
log.info("test close halfClose()");
}
@Override
public void cancel(String message, Throwable cause) {
log.info("test open cancel()");
super.cancel(message, cause);
log.info("test close cancel()");
}
};
}
}
如果仅仅是将ThreadLocal的值通过header向下传递，可以这样重写：
@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) {
injectHeadersFromScope(headers);
// @1 在Header中设置需要透传的值
super.start(responseListener, headers);
}
};
}
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