问题描述：

在spring boot的拦截器中，读取ServletRequest中的内容，抛出异常:getReader() has already been called for this request异常

原因：

ServletRequest的getReader()和getInputStream()两个方法只能被调用一次

解决办法:

先将 Request Body 保存，然后通过 Servlet 自带的 HttpServletRequestWrapper 类覆盖 getReader() 和getInputStream() 方法，使流从保存的body读取。然后再Filter中将ServletRequest替换为AuthenticationRequestWrapper。

public class MyRequestWrapper extends HttpServletRequestWrapper {
     private final String body;

    public MyRequestWrapper(HttpServletRequest request) throws IOException {
       super(request);

        StringBuilder sb = new StringBuilder();
        String line;
        BufferedReader reader = request.getReader();
        while ((line = reader.readLine()) != null) {
            sb.append(line);
        }
        // cache play load when create wrapper
        body = sb.toString();
    }
 
    public String getBody() {
        return body;
    }
}

try {
     MyRequestWrapper myRequestWrapper = new MyRequestWrapper(request);
     return myRequestWrapper.getBody();
} catch (IOException e) {
     log.error("get request body exception", e);
     throw new RuntimeException(e);
}