小程序批量上传图片方案

前言

 　　目前小程序的 wx.uploadFile 方法，还不支持批量上传，只能使用循环一个一个进行上传，对于某些特定需求，或者想节约带宽的时候，显然这种方式还是满足不了，下面提供一种方案解决批量上传问题，虽然不是最优方案，但是能实现一次请求上传多个图片。

思路

　　小程序批量选择完图片后，把图片转换为base64编码，然后push到数组当中，然后通过 wx.request 请求服务端接口，服务端接口对其进行base64解码，最好转换为file文件流。

小程序端代码

  /**
   * 通过wx.chooseImage选择后的fileList
   * @param {*} fileList 
   */
  upPic: function (fileList) {
    let file = []
    for(let i=0;i<fileList.length;i++){
      const fileSystemManager = wx.getFileSystemManager()
      const data = fileSystemManager.readFileSync(fileList[i].path,'base64')
      file.push('data:image/jpeg;base64,'+data)
    }
    wx.request({
      url: 'http://192.168.3.78:8080/sh-api-videos/video/selected/upload', 
      data: {
        fileList: file
      },
      method: 'POST',
      header: {
        'content-type': 'application/json'
      },
      success (res) {
        console.log(res.data)
      }
    })
  }

服务端代码（java示例）

    /**
     * 接受fileList的controller方法
     * @param upload
     * @throws IOException
     */
    @PostMapping(value="/upload",consumes=MediaType.APPLICATION_JSON_VALUE)
    @SaveLog
    public void upload(@RequestBody @Valid Upload upload) throws IOException {
        List<String> fileList = upload.getFileList();
        for (int i=0;i<fileList.size();i++) {
            String str = fileList.get(i);
            MultipartFile multipartFile = BASE64DecodedMultipartFile.base64ToMultipart(str);
            System.out.println(multipartFile.getName());
            System.out.println(multipartFile.getOriginalFilename());
            approvalFile(multipartFile);
        }
    }
    // 此处是保存文件到本地，不使用可忽略
    public void approvalFile( MultipartFile filecontent){
        OutputStream os = null;
        InputStream inputStream = null;
        String fileName = null;
        try {
            inputStream = filecontent.getInputStream();
            fileName = filecontent.getOriginalFilename();
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            String path = "/Users/whao/tmp/upload/";
            // 2、保存到临时文件
            // 1K的数据缓冲
            byte[] bs = new byte[1024];
            // 读取到的数据长度
            int len;
            // 输出的文件流保存到本地文件
            File tempFile = new File(path);
            if (!tempFile.exists()) {
                tempFile.mkdirs();
            }
            os = new FileOutputStream(tempFile.getPath() + File.separator + fileName);
            // 开始读取
            while ((len = inputStream.read(bs)) != -1) {
                os.write(bs, 0, len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 完毕，关闭所有链接
            try {
                os.close();
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

服务端代码 (Upload实体类)

package com.sh.api.video.model;

import java.util.List;

public class Upload {

    private List<String> fileList;


    public List<String> getFileList() {
        return fileList;
    }
    public void setFileList(List<String> fileList) {
        this.fileList = fileList;
    }
}

服务端代码 （base64转换为MultipartFile工具类）

package com.sh.api.video.utils;
import org.springframework.web.multipart.MultipartFile;
import sun.misc.BASE64Decoder;
import java.io.*;
/**
 * base64转MultipartFile
 */
public class BASE64DecodedMultipartFile implements MultipartFile {
    private final byte[] imgContent;
    private final String header;

    public BASE64DecodedMultipartFile(byte[] imgContent, String header) {
        this.imgContent = imgContent;
        this.header = header.split(";")[0];
    }

    @Override
    public String getName() {
        // TODO - implementation depends on your requirements
        return System.currentTimeMillis() + Math.random() + "." + header.split("/")[1];
    }

    @Override
    public String getOriginalFilename() {
        // TODO - implementation depends on your requirements
        return System.currentTimeMillis() + (int) Math.random() * 10000 + "." + header.split("/")[1];
    }

    @Override
    public String getContentType() {
        // TODO - implementation depends on your requirements
        return header.split(":")[1];
    }

    @Override
    public boolean isEmpty() {
        return imgContent == null || imgContent.length == 0;
    }

    @Override
    public long getSize() {
        return imgContent.length;
    }

    @Override
    public byte[] getBytes() throws IOException {
        return imgContent;
    }

    @Override
    public InputStream getInputStream() throws IOException {
        return new ByteArrayInputStream(imgContent);
    }

    @Override
    public void transferTo(File dest) throws IOException, IllegalStateException {
        new FileOutputStream(dest).write(imgContent);
    }

    /**
     * base64转MultipartFile文件
     *
     * @param base64
     * @return
     */
    public static MultipartFile base64ToMultipart(String base64) {
        try {
            String[] baseStrs = base64.split(",");
            BASE64Decoder decoder = new BASE64Decoder();
            byte[] b = new byte[0];
            b = decoder.decodeBuffer(baseStrs[1]);
            for (int i = 0; i < b.length; ++i) {
                if (b[i] < 0) {
                    b[i] += 256;
                }
            }
            return new BASE64DecodedMultipartFile(b, baseStrs[0]);
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

}