给RestTemplate加全局日志打印

原创

eeaters

发布于 2023-08-08 11:30:32

5150

发布于 2023-08-08 11:30:32

文章被收录于专栏：阿杰阿杰

项目中几乎所有的rpc调用都用了RestTemplate，日志并不完善，同事要对所有请求增加一个日志和响应的日志输出

选用了Interceptor进行RestTemplate的增强，碰到了流只能用一次的问题. 网上有两种解决的方向:

用拦截器 ClientHttpRequestInterceptor , 但是大多数文章没有解决流的一次性问题.
用工厂BufferingClientHttpRequestFactory , 但是代码限定了包装的是apache的HttpComponentsClientHttpRequestFactory .我没有这个包, 也不想莫名其妙的就引入这个包

因此决定撸一下源码给一个有理有据的解决方案

看下源码

RestTemplate

@Nullable
protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
        @Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
    //...
    try {
        //核心是createRequest构建的request中包含什么逻辑
        ClientHttpRequest request = createRequest(url, method);
        //执行的代码在request.execute()
        response = request.execute();
        handleResponse(url, method, response);
        return (responseExtractor != null ? responseExtractor.extractData(response) : null);
    }
    //...
}

protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
    ClientHttpRequest request = getRequestFactory().createRequest(url, method);
}

InterceptingHttpAccessor

RestTemplate继承的是该类.

@Override
    public ClientHttpRequestFactory getRequestFactory() {
        List<ClientHttpRequestInterceptor> interceptors = getInterceptors();
        if (!CollectionUtils.isEmpty(interceptors)) {
            ClientHttpRequestFactory factory = this.interceptingRequestFactory;
            if (factory == null) {
                factory = new InterceptingClientHttpRequestFactory(super.getRequestFactory(), interceptors);
                this.interceptingRequestFactory = factory;
            }
            return factory;
        }
        else {
            return super.getRequestFactory();
        }
    }

InterceptingClientHttpRequestFactory

requestTemplate进行远程调用时, 会走到InterceptingClientHttpRequest.execute方法,内部再链到executeInternal上

class InterceptingClientHttpRequest extends AbstractBufferingClientHttpRequest {

    private final ClientHttpRequestFactory requestFactory;

    private final List<ClientHttpRequestInterceptor> interceptors;
    
    //父类中执行execute时,会调用到子类的executeInternal方法
    @Override
    protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
        InterceptingRequestExecution requestExecution = new InterceptingRequestExecution();
        return requestExecution.execute(this, bufferedOutput);
    }

}

InterceptingRequestExecution

private class InterceptingRequestExecution implements ClientHttpRequestExecution {

    private final Iterator<ClientHttpRequestInterceptor> iterator;

    public InterceptingRequestExecution() {
        this.iterator = interceptors.iterator();
    }

    @Override
    public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
        if (this.iterator.hasNext()) {
            ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
            return nextInterceptor.intercept(request, body, this);
        }
        else {
            HttpMethod method = request.getMethod();
            Assert.state(method != null, "No standard HTTP method");
            ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
            //...
            return delegate.execute();
        }
    }
}

执行时序图

选择方案-RequestFactory

如果需要对响应流进行包装实现可重用. 最佳的位置有两处: 最后一个interceptor或者delegate本身返回的就是可重用流

这里就想到了网上提到的 BufferingClientHttpRequestFactory , 这是源码自身提供的支持, 只不过由于这个功能应该不是通用的功能但是会多占用内存, 因此提供支持, 但是是否用就看开发者本身了

RestTemplateBuilder

public ClientHttpRequestFactory buildRequestFactory() {
        ClientHttpRequestFactory requestFactory = null;
        if (this.requestFactory != null) {
            requestFactory = this.requestFactory.get();
        }
        else if (this.detectRequestFactory) {
            requestFactory = new ClientHttpRequestFactorySupplier().get();
        }
        if (requestFactory != null) {
            if (this.requestFactoryCustomizer != null) {
                this.requestFactoryCustomizer.accept(requestFactory);
            }
        }
        return requestFactory;
    }

ClientHttpRequestFactorySupplier

public class ClientHttpRequestFactorySupplier implements Supplier<ClientHttpRequestFactory> {

    private static final Map<String, String> REQUEST_FACTORY_CANDIDATES;

    static {
        Map<String, String> candidates = new LinkedHashMap<>();
        candidates.put("org.apache.http.client.HttpClient",
                "org.springframework.http.client.HttpComponentsClientHttpRequestFactory");
        candidates.put("okhttp3.OkHttpClient", "org.springframework.http.client.OkHttp3ClientHttpRequestFactory");
        REQUEST_FACTORY_CANDIDATES = Collections.unmodifiableMap(candidates);
    }

    //根据引入的依赖决定加载的是什么工厂
    @Override
    public ClientHttpRequestFactory get() {
        for (Map.Entry<String, String> candidate : REQUEST_FACTORY_CANDIDATES.entrySet()) {
            ClassLoader classLoader = getClass().getClassLoader();
            if (ClassUtils.isPresent(candidate.getKey(), classLoader)) {
                Class<?> factoryClass = ClassUtils.resolveClassName(candidate.getValue(), classLoader);
                return (ClientHttpRequestFactory) BeanUtils.instantiateClass(factoryClass);
            }
        }
        return new SimpleClientHttpRequestFactory();
    }
}

最终测试代码

 @Test
    public void test() {
        RestTemplate restTemplate = new RestTemplate();
        ClientHttpRequestFactory clientHttpRequestFactory = new ClientHttpRequestFactorySupplier().get();
        restTemplate.setRequestFactory(new BufferingClientHttpRequestFactory(clientHttpRequestFactory));
        restTemplate.getInterceptors().add(new LoggingInterceptor());

        String forObject = restTemplate.getForObject("http://www.baidu.com", String.class);
        System.out.println("forObject = " + forObject);
    }

    //这时候所有的拦截器都可以将body获取到随便用了
    public class LoggingInterceptor implements ClientHttpRequestInterceptor {
        @Override
        public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
            ClientHttpResponse execute = execution.execute(request, body);
            System.out.println("body = " + new String(execute.getBody().readAllBytes()));
            System.out.println("body = " + new String(execute.getBody().readAllBytes()));
            return execute;
        }
    }

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