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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
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
close流，读取完之后再reset流ClientHttpResponse每次调用getBody都返回一个新的输入流// 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。
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。
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：
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