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使用场景：在接口处理之前，我们需要拿到请求参数，对参数进行校验。注意，这里需要拿到的是原始的请求信息！

一般的获取方式

ServletInputStream inputStream = request.getInputStream();
StringBuilder stringBuilder = new StringBuilder();
try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, request.getCharacterEncoding()))) {String line;while ((line = reader.readLine()) != null) {stringBuilder.append(line);}
} catch (IOException e) {e.printStackTrace();
}
String requestBody = stringBuilder.toString();

获取requestBody的代码大同小异，可自行搜索。代码没有问题，但是无法获取到requestBody，就要考虑接口方法是否使用了@RequestBody。

在Spring MVC框架中，当你使用@RequestBody注解时，Spring会在将请求转发到控制器方法之前，从HTTP请求体中读取数据并将其反序列化为Java对象。这一处理过程是由HttpMessageConverter完成的，它负责将请求体中的JSON、XML或其他格式的数据转换为Java对象。

请求体只能被读取一次：HTTP请求体是一个输入流，它只能被读取一次。一旦HttpMessageConverter读取了请求体，输入流就被“消耗”掉了，无法再次被读取。因此，当切面尝试访问请求体时，它发现输入流已经为空或不可用。

解决方法：

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;public class CachedBodyHttpServletRequestWrapper extends HttpServletRequestWrapper {private final byte[] cachedBody;public CachedBodyHttpServletRequestWrapper(HttpServletRequest request) throws IOException {super(request);ByteArrayOutputStream outputStream = new ByteArrayOutputStream();InputStream inputStream = request.getInputStream();byte[] buffer = new byte[1024];int bytesRead;while ((bytesRead = inputStream.read(buffer)) != -1) {outputStream.write(buffer, 0, bytesRead);}cachedBody = outputStream.toByteArray();}@Overridepublic ServletInputStream getInputStream() throws IOException {final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(cachedBody);return new ServletInputStream() {@Overridepublic boolean isFinished() {return byteArrayInputStream.available() == 0;}@Overridepublic boolean isReady() {return true;}@Overridepublic void setReadListener(ReadListener readListener) {}@Overridepublic int read() throws IOException {return byteArrayInputStream.read();}};}public String getCachedBody() {return new String(cachedBody, StandardCharsets.UTF_8);}
}

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;public class CachedBodyFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)throws IOException, ServletException {if (request instanceof HttpServletRequest) {HttpServletRequest httpRequest = (HttpServletRequest) request;CachedBodyHttpServletRequestWrapper cachedBodyRequestWrapper = new CachedBodyHttpServletRequestWrapper(httpRequest);chain.doFilter(cachedBodyRequestWrapper, response);} else {chain.doFilter(request, response);}}@Overridepublic void destroy() {}
}

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class FilterConfig {@Beanpublic FilterRegistrationBean<CachedBodyFilter> loggingFilter(){FilterRegistrationBean<CachedBodyFilter> registrationBean = new FilterRegistrationBean<>();registrationBean.setFilter(new CachedBodyFilter());registrationBean.addUrlPatterns("/*");return registrationBean;    }
}

然后在切面里利用CachedBodyHttpServletRequestWrapper 去获取requestBody就可以了。