摘要：在使用開發(fā)的時候希望把，，等等的信息記錄到我們的日志中，方便我們排查問題，也能對系統(tǒng)的數(shù)據(jù)做一些統(tǒng)計。使用了來攔截并分發(fā)請求，我們只要自己實現(xiàn)一個并在其中對請求和響應做處理打印到日志中即可。

在使用Spring Boot開發(fā) web api 的時候希望把 request，request header ，response reponse header , uri, method 等等的信息記錄到我們的日志中，方便我們排查問題，也能對系統(tǒng)的數(shù)據(jù)做一些統(tǒng)計。

Spring 使用了 DispatcherServlet 來攔截并分發(fā)請求，我們只要自己實現(xiàn)一個 DispatcherServlet 并在其中對請求和響應做處理打印到日志中即可。

我們實現(xiàn)一個自己的分發(fā) Servlet ，它繼承于 DispatcherServlet，我們實現(xiàn)自己的 doDispatch(HttpServletRequest request, HttpServletResponse response) 方法。

public class LoggableDispatcherServlet extends DispatcherServlet {

    private static final Logger logger = LoggerFactory.getLogger("HttpLogger");

    private static final ObjectMapper mapper = new ObjectMapper();

    @Override
    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ContentCachingRequestWrapper requestWrapper = new ContentCachingRequestWrapper(request);
        ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(response);
        //創(chuàng)建一個 json 對象，用來存放 http 日志信息
        ObjectNode rootNode = mapper.createObjectNode();
        rootNode.put("uri", requestWrapper.getRequestURI());
        rootNode.put("clientIp", requestWrapper.getRemoteAddr());
        rootNode.set("requestHeaders", mapper.valueToTree(getRequestHeaders(requestWrapper)));
        String method = requestWrapper.getMethod();
        rootNode.put("method", method);
        try {
            super.doDispatch(requestWrapper, responseWrapper);
        } finally {
            if(method.equals("GET")) {
                rootNode.set("request", mapper.valueToTree(requestWrapper.getParameterMap()));
            } else {
                JsonNode newNode = mapper.readTree(requestWrapper.getContentAsByteArray());
                rootNode.set("request", newNode);
            }

            rootNode.put("status", responseWrapper.getStatus());
            JsonNode newNode = mapper.readTree(responseWrapper.getContentAsByteArray());
            rootNode.set("response", newNode);

            responseWrapper.copyBodyToResponse();

            rootNode.set("responseHeaders", mapper.valueToTree(getResponsetHeaders(responseWrapper)));
            logger.info(rootNode.toString());
        }
    }

    private Map getRequestHeaders(HttpServletRequest request) {
        Map headers = new HashMap<>();
        Enumeration headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            headers.put(headerName, request.getHeader(headerName));
        }
        return headers;

    }

    private Map getResponsetHeaders(ContentCachingResponseWrapper response) {
        Map headers = new HashMap<>();
        Collection headerNames = response.getHeaderNames();
        for (String headerName : headerNames) {
            headers.put(headerName, response.getHeader(headerName));
        }
        return headers;
    }

在 LoggableDispatcherServlet 中，我們可以通過 HttpServletRequest 中的 InputStream 或 reader 來獲取請求的數(shù)據(jù)，但如果我們直接在這里讀取了流或內(nèi)容，到后面的邏輯將無法進行下去，所以需要實現(xiàn)一個可以緩存的 HttpServletRequest。好在 Spring 提供這樣的類，就是 ContentCachingRequestWrapper 和 ContentCachingResponseWrapper， 根據(jù)官方的文檔這兩個類正好是來干這個事情的，我們只要將 HttpServletRequest 和 HttpServletResponse 轉化即可。

HttpServletRequest wrapper that caches all content read from the input stream and reader, and allows this content to be retrieved via a byte array.
Used e.g. by AbstractRequestLoggingFilter. Note: As of Spring Framework 5.0, this wrapper is built on the Servlet 3.1 API.
HttpServletResponse wrapper that caches all content written to the output stream and writer, and allows this content to be retrieved via a byte array.
Used e.g. by ShallowEtagHeaderFilter. Note: As of Spring Framework 5.0, this wrapper is built on the Servlet 3.1 API.

實現(xiàn)好我們的 LoggableDispatcherServlet后，接下來就是要指定使用 LoggableDispatcherServlet 來分發(fā)請求。

@SpringBootApplication
public class SbDemoApplication implements ApplicationRunner {

    public static void main(String[] args) {
        SpringApplication.run(SbDemoApplication.class, args);
    }
    @Bean
    public ServletRegistrationBean dispatcherRegistration() {
        return new ServletRegistrationBean(dispatcherServlet());
    }
    @Bean(name = DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
    public DispatcherServlet dispatcherServlet() {
        return new LoggableDispatcherServlet();
    }
}

增加一個簡單的 Controller 來測試一下

@RestController
@RequestMapping("/hello")
public class HelloController {

    @RequestMapping(value = "/word", method = RequestMethod.POST)
    public Object hello(@RequestBody Object object) {
        return object;
    }
}

使用 curl 發(fā)送一個 Post 請求：

$ curl --header "Content-Type: application/json" 
  --request POST 
  --data "{"username":"xyz","password":"xyz"}" 
  http://localhost:8080/hello/word
{"username":"xyz","password":"xyz"}

查看打印的日志：

{
    "uri":"/hello/word",
    "clientIp":"0:0:0:0:0:0:0:1",
    "requestHeaders":{
        "content-length":"35",
        "host":"localhost:8080",
        "content-type":"application/json",
        "user-agent":"curl/7.54.0",
        "accept":"*/*"
    },
    "method":"POST",
    "request":{
        "username":"xyz",
        "password":"xyz"
    },
    "status":200,
    "response":{
        "username":"xyz",
        "password":"xyz"
    },
    "responseHeaders":{
        "Content-Length":"35",
        "Date":"Sun, 17 Mar 2019 08:56:50 GMT",
        "Content-Type":"application/json;charset=UTF-8"
    }
}

當然打印出來是在一行中的，我進行了一下格式化。我們還可以在日志中增加請求的時間，耗費的時間以及異常信息等。