java Excel文件生成后转MultipartFile 完成文件上传。

淡淡的烟草味﹌ 2022-04-18 05:59 1264阅读 0赞

由于需求。。

使用了ByteArrayOutputStream和ByteArrayInputStream类.  
**将XSSFWorkbook 写入ByteArrayOutputStream.然后用ByteArrayOutputStream来转换为字节流.然后再将字节流转换为ByteArrayInputStream …至此,我们就在内存中将excel转换成了输入流…**  
话不多说，上代码：

//wb   为 XSSFWorkbook wb = new XSSFWorkbook();//创建一个Workbook
       //由于生成Excel代码太多... 
       ByteArrayOutputStream os = new ByteArrayOutputStream();
            try {
                wb.write(os);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            byte[] b = os.toByteArray();
            ByteArrayInputStream in = new ByteArrayInputStream(b);
            String  strBase64 = ioToBase64(in);
            MultipartFile file = base64ToMultipart(strBase64);
            
            然后通过MultipartFile完成文件上传。..

// io转base64 
    public static String ioToBase64(InputStream in) throws IOException {
            String strBase64 = null;
            try{
                 //in.available()//返回文件的字节长度
                byte[] bytes = new byte[in.available()];
                in.read(bytes);
                // 将文件中的内容读入到数组中
                strBase64 = new BASE64Encoder().encode(bytes);   //将字节流数组转换为字符串
                in.close();
            }catch (IOException e) {
                    e.printStackTrace();
                }
                return strBase64;
            }
    
    
        public static MultipartFile base64ToMultipart(String base64) {
            try {
                BASE64Decoder decoder = new BASE64Decoder();
                byte[] b = decoder.decodeBuffer(base64);
                for (int i = 0; i < b.length; ++i) {
                    if (b[i] < 0) {
                        b[i] += 256;
                    }
                }
                return new BASE64DecodedMultipartFile(b, base64);
            } catch (Exception e) {
                e.printStackTrace();
                return null;
            }
        }

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);
        }
    }

参考博客：  
[https://blog.csdn.net/u011109420/article/details/51330677][https_blog.csdn.net_u011109420_article_details_51330677]  
[https://blog.csdn.net/qq\_37861937/article/details/78218547][https_blog.csdn.net_qq_37861937_article_details_78218547]  
[https://blog.csdn.net/izb2008/article/details/79623234][https_blog.csdn.net_izb2008_article_details_79623234]

[https_blog.csdn.net_u011109420_article_details_51330677]: https://blog.csdn.net/u011109420/article/details/51330677
[https_blog.csdn.net_qq_37861937_article_details_78218547]: https://blog.csdn.net/qq_37861937/article/details/78218547
[https_blog.csdn.net_izb2008_article_details_79623234]: https://blog.csdn.net/izb2008/article/details/79623234