将base64格式的图片字符串转换成MultipartFile

转自：https://www.jianshu.com/p/d9c16b3ffd3c

byte[] decode = Base64.getDecoder().decode(imgFile);
String img = new String(decode);
log.info("上传图片......");
MultipartFile file = ImageUtils.base64ToMultipartFile(img);

创建两个java文件：ImageUtils、Base64DecodeMultipartFile

import org.apache.commons.codec.binary.Base64;
import org.springframework.web.multipart.MultipartFile;

public class ImageUtils {
    public static MultipartFile base64ToMultipartFile(String base64) {
        //base64编码后的图片有头信息所以要分离出来 [0]data:image/png;base64, 图片内容为索引[1]
        String[] baseStrs = base64.split(",");

        //取索引为1的元素进行处理
        byte[] b = Base64.decodeBase64(baseStrs[1]);
        for (int i = 0; i < b.length; ++i) {
            if (b[i] < 0) {
                b[i] += 256;
            }
        }

        //处理过后的数据通过Base64DecodeMultipartFile转换为MultipartFile对象
        return new Base64DecodeMultipartFile(b, baseStrs[0]);
    }
}

import org.springframework.web.multipart.MultipartFile;
import java.io.*;

public class Base64DecodeMultipartFile implements MultipartFile {
    private final byte[] imgContent;
    private final String header;

    public Base64DecodeMultipartFile(byte[] imgContent, String header) {
        this.imgContent = imgContent;
        this.header = header.split(";")[0];
    }

    @Override
    public String getName() {
        return System.currentTimeMillis() + Math.random() + "." + header.split("/")[1];
    }

    @Override
    public String getOriginalFilename() {
        return System.currentTimeMillis() + (int) Math.random() * 10000 + "." + header.split("/")[1];
    }

    @Override
    public String getContentType() {
        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);
    }
}