[alibaba/fastjson]JavaBean中存在MultipartFile属性时，调用JSONObject.toJSONString(javaBean)导致异常

JavaBean——User

import lombok.Data;
import org.springframework.web.multipart.MultipartFile;

@Data
public class User {
    private int id;
    private MultipartFile file;
}

异常调用

controller接收到前端传来的id和file后，实例化上图的User，在调用方法JSONObject.toJSONString(user);时就会有异常产生。

@PostMapping("/upload")
public String uploadFile(@RequestParam int id, @RequestParam MultipartFile file){
        User user = new User();
        user.setId(id);
        user.setFile(file);
        JSONObject.toJSONString(user);
        return null;
}

异常

java.io.FileNotFoundException: MultipartFile resource [file] cannot be resolved to absolute file path
    at org.springframework.core.io.AbstractResource.getFile(AbstractResource.java:138) ~[spring-core-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
    at com.alibaba.fastjson.util.FieldInfo.get(FieldInfo.java:564) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.FieldSerializer.getPropertyValueDirect(FieldSerializer.java:145) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:282) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:149) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.FieldSerializer.writeValue(FieldSerializer.java:320) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:470) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.JavaBeanSerializer.write(JavaBeanSerializer.java:149) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.JSONSerializer.writeWithFieldName(JSONSerializer.java:360) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.serializer.ASMSerializer_1_User.write(Unknown Source) ~[na:na]
    at com.alibaba.fastjson.serializer.JSONSerializer.write(JSONSerializer.java:312) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.JSON.toJSONString(JSON.java:769) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.JSON.toJSONString(JSON.java:707) ~[fastjson-1.2.73.jar:na]
    at com.alibaba.fastjson.JSON.toJSONString(JSON.java:672) ~[fastjson-1.2.73.jar:na]
    at com.charon.springlearn.controller.Controller1.uploadFile(Controller1.java:55) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_181]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:878) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:792) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) ~[tomcat-embed-core-9.0.38.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.38.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.9.RELEASE.jar:5.2.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_181]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_181]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.38.jar:9.0.38]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_181]

jeffren1997

debug了代码，发现了原因

fastjson在打印JSON字符串时，会通过反射得到一个object的所有getter方法，然后取其值，最后拼装成一个JSON字符串。
MultipartFile对象有一个 Resource getResource() 方法

default Resource getResource() {
    return new MultipartFileResource(this);
}

fastjson在得到Resource后，会继续对Resource对象进行遍历
Resource是一个接口，其中有个 getFile 方法

File getFile() throws IOException;

MultipartFileResource本身并没有对 getFile 进行重写

查看父类中的 getFile 方法

public File getFile() throws IOException {
throw new FileNotFoundException(this.getDescription() + " cannot be resolved to absolute file path");
}

解惑！

jeffren1997

所以楼主是怎么解决的

Guanyong-Liang

解决了嘛?

EricFengFuuuu

不建议对MultipartFile对象进行序列化/反序列化操作，加注解把它排除掉

LSL1618

我们这需要将MultipartFile文件通过dubbo传输，必须要将MultipartFile序列化，不然通不过dubbo协议，有什么好思路嘛，本来使用JSON.toJSONString()，但是会爆同上的错误

Liudiey

我们这需要将MultipartFile文件通过dubbo传输，必须要将MultipartFile序列化，不然通不过dubbo协议，有什么好思路嘛，本来使用JSON.toJSONString()，但是会爆同上的错误

User类中能否试试定义MultipartFile的实现类属性CommonsMultipartFile或者StandardMultipartFile

或者试试能否排除掉MultipartFile中的某个get方法，它没有属性好像没办法排除。

LSL1618

[alibaba/fastjson]JavaBean中存在MultipartFile属性时，调用JSONObject.toJSONString(javaBean)导致异常

回答