异常处理：getReader() has already been called for this request

场景描述：

    在 Spring Boot 自定义拦截器中，需要对请求 body 中的内容做签名验证。在日志切面中，需要打印请求 body 中的内容。

报错内容：

java.lang.IllegalStateException: getReader() has already been called for this request
    at org.apache.catalina.connector.Request.getInputStream(Request.java:1069)
    at org.apache.catalina.connector.RequestFacade.getInputStream(RequestFacade.java:365)
    at com.igg.aggregate.server.aspect.LogAspect.before(LogAspect.java:80)

自己的报错（想把getReader输出两遍）

java.lang.IllegalStateException: getReader() has already been called for this request
    org.apache.catalina.connector.Request.getInputStream(Request.java:1032)
    org.apache.catalina.connector.RequestFacade.getInputStream(RequestFacade.java:364)
    org.apache.commons.fileupload.servlet.ServletRequestContext.getInputStream(ServletRequestContext.java:112)
    org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.<init>(FileUploadBase.java:952)
    org.apache.commons.fileupload.FileUploadBase.getItemIterator(FileUploadBase.java:310)
    org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:334)
    org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:115)
    com.cc8w.controller.TestController.upload(TestController.java:68)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:498)

 

原因分析：

    HttpServletRequest 的 getInputStream() 和 getReader() 都只能读取一次，由于 Request Body 是流的形式读取，那么

流读了一次就没有了，所以只能被调用一次。

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。

代码示例：

public class MyRequestWrapper extends HttpServletRequestWrapper {
    private byte[] 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);
        }
        String body = sb.toString();
        this.body = body.getBytes(StandardCharsets.UTF_8);
    }


    public String getBody() {
        return new String(body, StandardCharsets.UTF_8);
    }
}

 

 

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