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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);    }}@Slf4jclass 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('\n');                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
   
     values = entry.getValue();                    return "\t" + entry.getKey() + ":" + (values.size() == 1 ?                            "\"" + values.get(0) + "\"" :                            values.stream().map(s -> "\"" + s + "\"").collect(Collectors.joining(", ")));                })                .collect(Collectors.joining(", \n", "\n[\n", "\n]\n"));    }}
   

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

1. 改写代码，不close流，读取完之后再reset流
2. 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('\n');    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

1. 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。

@Slf4jclass 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('\n');                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。

2. 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);    }}@Slf4jclass 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('\n');                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