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使用RestTemplate，显示请求信息，响应信息

这里不讲怎么用RestTemplate具体细节用法，就是一个学习中的过程记录

一个简单的例子

public class App {
    public static void main(String[] args) {
        String url = "https://api.uixsj.cn/hitokoto/get";
        RestTemplate restTemplate = new RestTemplate();
        String body = restTemplate.getForObject(url, String.class);
        System.out.println(body);
    }
}

运行结果：

❓：现在我想看看他的请求头，请求参数，响应头，响应体的详细信息是怎么样子的，这样也方便以后检查请求参数是否完整，响应正确与否。

经过搜集资料发现ClientHttpRequestInterceptor满足需求，于是就有了下面的代码

打印请求头/响应头

public class App {
    public static void main(String[] args) {
        String url = "https://api.uixsj.cn/hitokoto/get";
        RestTemplate restTemplate = new RestTemplate();
        // 加上拦截器打印将请求请求，响应信息打印出来
        restTemplate.setInterceptors(Collections.singletonList(new LoggingInterceptor()));
        String body = restTemplate.getForObject(url, String.class);
        System.out.println(body);
    }
}

@Slf4j
class LoggingInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        displayRequest(request, body);
        ClientHttpResponse response = execution.execute(request, body);
        displayResponse(response);
        return response;
    }

    /**
     * 显示请求相关信息
     * @param request
     * @param body
     */
    private void displayRequest(HttpRequest request, byte[] body) {
        log.debug("====request info====");
        log.debug("URI         : {}", request.getURI());
        log.debug("Method      : {}", request.getMethod());
        log.debug("Req Headers : {}", this.headersToString(request.getHeaders()));
        log.debug("Request body: {}", body == null ? "" : new String(body, StandardCharsets.UTF_8));
    }

    /**
     * 显示响应相关信息
     * @param response
     * @throws IOException
     */
    private void displayResponse(ClientHttpResponse response) throws IOException {
        StringBuilder inputStringBuilder = new StringBuilder();
        try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(response.getBody(), StandardCharsets.UTF_8))) {
            String line = bufferedReader.readLine();
            while (line != null) {
                inputStringBuilder.append(line);
                inputStringBuilder.append('
');
                line = bufferedReader.readLine();
            }
        }
        log.debug("====response info====");
        log.debug("Status code  : {}", response.getStatusCode());
        log.debug("Status text  : {}", response.getStatusText());
        log.debug("Resp Headers : {}", headersToString(response.getHeaders()));
        log.debug("Response body: {}", inputStringBuilder.toString());
    }

    /**
     * 将Http头信息格式化处理
     * @param httpHeaders
     * @return
     */
    private String headersToString(HttpHeaders httpHeaders) {
        if (Objects.isNull(httpHeaders)) {
            return "[]";
        }
        return httpHeaders.entrySet().stream()
                .map(entry -> {
                    List<String> values = entry.getValue();
                    return "	" + entry.getKey() + ":" + (values.size() == 1 ?
                            """ + values.get(0) + """ :
                            values.stream().map(s -> """ + s + """).collect(Collectors.joining(", ")));
                })
                .collect(Collectors.joining(", 
", "
[
", "
]
"));
    }
}

运行结果：

执行过程中会报错，具体错误信息是

Exception in thread "main" org.springframework.web.client.ResourceAccessException: I/O error on GET request for "https://api.uixsj.cn/hitokoto/get": stream is closed; nested exception is java.io.IOException: stream is closed

这里报错信息是流已关闭，报错是在添加LoggingInterceptor后出现的，那就是新加代码引起的。在看看LoggingInterceptor的实现，什么地方操作了流，并且关闭了流。

LoggingInterceptor.displayResponse这个方法里面，为了读取响应体操作了流response.getBody()，

try (...) {
}
// 这个try块结束后就把流给关了

注释掉代码中流操作相关代码，再次运行没有错误信息。因该是在拦截器后，RestTemplate也需要操作了response.getBody()的流（废话）。

Response body 不能读第二次这个很要命呀

问题找到了，初步的想到了几种解决

改写代码，不close流，读取完之后再reset流
代理一下ClientHttpResponse每次调用getBody都返回一个新的输入流

解决不能重复读Response body

方法一：读取完后不关闭流

// 略...
InputStream responseBody = response.getBody();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(responseBody, StandardCharsets.UTF_8));
String line = bufferedReader.readLine();
while (line != null) {
    inputStringBuilder.append(line);
    inputStringBuilder.append('
');
    line = bufferedReader.readLine();
}
responseBody.reset();
// 略...

很遗憾，执行后依旧有错误

Exception in thread "main" org.springframework.web.client.ResourceAccessException: I/O error on GET request for "https://api.uixsj.cn/hitokoto/get": mark/reset not supported; nested exception is java.io.IOException: mark/reset not supported

说的很清楚，不支持mark/reset方法。很明显了它不允许随意修改读取定位。没办法只转为第二种方法了。

方法二：代理，每次都返回一个新的流

静态代理实现ClientHttpResponse接口，好在ClientHttpResponse实现的接口数量不多，实现的代码如下。

@Slf4j
class LoggingInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        displayRequest(request, body);
        ClientHttpResponse response = execution.execute(request, body);
        // 包装代理一下
        response = new ClientHttpResponseWrapper(response);
        displayResponse(response);
        return response;
    }

    /**
     * 显示请求相关信息
     * @param request
     * @param body
     */
    private void displayRequest(HttpRequest request, byte[] body) {
        // 略...
    }

    /**
     * 显示响应相关信息
     * @param response
     * @throws IOException
     */
    private void displayResponse(ClientHttpResponse response) throws IOException {
        StringBuilder inputStringBuilder = new StringBuilder();
        try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(response.getBody(), StandardCharsets.UTF_8))) {
            String line = bufferedReader.readLine();
            while (line != null) {
                inputStringBuilder.append(line);
                inputStringBuilder.append('
');
                line = bufferedReader.readLine();
            }
        }
        // 略...
    }

    /**
     * 将Http头信息格式化处理
     * @param httpHeaders
     * @return
     */
    private String headersToString(HttpHeaders httpHeaders) {
        // 略...
    }

    private class ClientHttpResponseWrapper implements ClientHttpResponse {
        private ClientHttpResponse clientHttpResponse;
        private byte[] body;

        public ClientHttpResponseWrapper(ClientHttpResponse clientHttpResponse) {
            this.clientHttpResponse = clientHttpResponse;
        }

        @Override
        public HttpStatus getStatusCode() throws IOException {
            return this.clientHttpResponse.getStatusCode();
        }

        @Override
        public int getRawStatusCode() throws IOException {
            return this.clientHttpResponse.getRawStatusCode();
        }

        @Override
        public String getStatusText() throws IOException {
            return this.clientHttpResponse.getStatusText();
        }

        @Override
        public void close() {
            this.clientHttpResponse.close();
        }

        /**
         * 缓存body每次返回一个新的输入流
         * @return
         * @throws IOException
         */
        @Override
        public InputStream getBody() throws IOException {
            if (Objects.isNull(this.body)) {
                this.body = StreamUtils.copyToByteArray(this.clientHttpResponse.getBody());
            }
            return new ByteArrayInputStream(this.body == null ? new byte[0] : this.body);
        }

        @Override
        public HttpHeaders getHeaders() {
            return this.clientHttpResponse.getHeaders();
        }
    }
}

运行效果：

代码运行没问题，但是总感觉代码写出来笨笨的，要重写这么多用不着的方法，看着不舒服，换个写法。

动态代理


public class App {
    public static void main(String[] args) {
        String url = "https://api.uixsj.cn/hitokoto/get";
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.setInterceptors(Collections.singletonList(new LoggingInterceptor()));
        String body = restTemplate.getForObject(url, String.class);
        System.out.println(body);
    }

}

@Slf4j
class LoggingInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        displayRequest(request, body);
        ClientHttpResponse response = execution.execute(request, body);
        // 包装代理一下
        response = (ClientHttpResponse) Proxy.newProxyInstance(response.getClass().getClassLoader(), new Class[]{ClientHttpResponse.class}, new ClientHttpResponseHandler(response));
        displayResponse(response);
        return response;
    }

    /**
     * 显示请求相关信息
     * @param request
     * @param body
     */
    private void displayRequest(HttpRequest request, byte[] body) {
        // 略......
    }

    /**
     * 显示响应相关信息
     * @param response
     * @throws IOException
     */
    private void displayResponse(ClientHttpResponse response) throws IOException {
        StringBuilder inputStringBuilder = new StringBuilder();
        try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(response.getBody(), StandardCharsets.UTF_8))) {
            String line = bufferedReader.readLine();
            while (line != null) {
                inputStringBuilder.append(line);
                inputStringBuilder.append('
');
                line = bufferedReader.readLine();
            }
        }
        // 略......
    }

    /**
     * 将Http头信息格式化处理
     * @param httpHeaders
     * @return
     */
    private String headersToString(HttpHeaders httpHeaders) {
        // 略......
    }

    private static class ClientHttpResponseHandler implements InvocationHandler {
        private static final String methodName = "getBody";
        private ClientHttpResponse clientHttpResponse;
        private byte[] body;

        ClientHttpResponseHandler(ClientHttpResponse clientHttpResponse) {
            this.clientHttpResponse = clientHttpResponse;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (StringUtils.equals(methodName, method.getName())) {
                if (Objects.isNull(this.body)) {
                    this.body = StreamUtils.copyToByteArray(this.clientHttpResponse.getBody());
                }
                return new ByteArrayInputStream(this.body == null ? new byte[0] : this.body);
            }
            return method.invoke(this.clientHttpResponse, args);
        }
    }
}

运行结果：

总结

使用RestTemplate想要显示详细请求信息，和响应信息
添加拦截器
拦截器中操作InputSteam导致流关闭，不能重复读Response body
尝试不关闭流，重置流的方案失败
使用代理解决 Response body 不能读第二次读的问题
- 静态代理（可以重复读Response body了）
- 动态代理（可以重复读Response body了）
静态代理的代码有点啰嗦，动态代理又有点不够味

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原文地址：https://www.cnblogs.com/pi-laoban/p/14071279.html

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