React.js，如何将多部分/表单数据发送到服务器

问题描述

我们想将图像文件作为多部分/表单发送到后端，我们尝试使用html表单获取文件并将文件作为formData发送，这是代码

We want to send an image file as multipart/form to the backend, we try to use html form to get file and send the file as formData, here are the codes

export default class Task extends React.Component {

  uploadAction() {
    var data = new FormData();
    var imagedata = document.querySelector('input[type="file"]').files[0];
    data.append("data", imagedata);

    fetch("http://localhost:8910/taskCreationController/createStoryTask", {
      mode: 'no-cors',
      method: "POST",
      headers: {
        "Content-Type": "multipart/form-data"
        "Accept": "application/json",
        "type": "formData"
      },
      body: data
    }).then(function (res) {
      if (res.ok) {
        alert("Perfect! ");
      } else if (res.status == 401) {
        alert("Oops! ");
      }
    }, function (e) {
      alert("Error submitting form!");
    });
  }

  render() {
    return (
        <form encType="multipart/form-data" action="">
          <input type="file" name="fileName" defaultValue="fileName"></input>
          <input type="button" value="upload" onClick={this.uploadAction.bind(this)}></input>
        </form>
    )
  }
}

后端错误为嵌套异常为org.springframework.web.multipart.MultipartException:无法解析多部分servlet请求；嵌套异常为java.io.IOException:org.apache.tomcat.util.http .fileupload.FileUploadException:由于未找到多部分边界，因此请求被拒绝."

阅读此后，我们尝试了设置获取时标头的边界:

After reading this, we tried to set boundary to headers in fetch:

fetch("http://localhost:8910/taskCreationController/createStoryTask", {
      mode: 'no-cors',
      method: "POST",
      headers: {
        "Content-Type": "multipart/form-data; boundary=AaB03x" +
        "--AaB03x" +
        "Content-Disposition: file" +
        "Content-Type: png" +
        "Content-Transfer-Encoding: binary" +
        "...data... " +
        "--AaB03x--",
        "Accept": "application/json",
        "type": "formData"
      },
      body: data
    }).then(function (res) {
      if (res.ok) {
        alert("Perfect! ");
      } else if (res.status == 401) {
        alert("Oops! ");
      }
    }, function (e) {
      alert("Error submitting form!");
    });
  }

这一次，后端中的错误是:在路径为[]的上下文中，servlet [dispatcherServlet]的Servlet.service()引发了异常[请求处理失败；嵌套异常是具有根本原因的java.lang.NullPointerException]

This time, the error in backend is: Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

我们是否添加多部分边界权?应该在哪里?也许起初我们是错误的，因为我们没有获得multipart/form-data.我们如何才能正确获得它?

Do we add the multipart boundary right? Where should it be?Maybe we are wrong at first because we don't get the multipart/form-data. How can we get it correctly?

推荐答案

我们只是尝试删除标题即可，并​​且有效！

We just try to remove our headers and it works!

fetch("http://localhost:8910/taskCreationController/createStoryTask", {
      mode: 'no-cors',
      method: "POST",
      body: data
    }).then(function (res) {
      if (res.ok) {
        alert("Perfect! ");
      } else if (res.status == 401) {
        alert("Oops! ");
      }
    }, function (e) {
      alert("Error submitting form!");
    });

这篇关于React.js，如何将多部分/表单数据发送到服务器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！