如何在Spring Boot（Java）中解码base64中的文件？

Question

我正在通过web服务将文件从前端（Angular）发送到后端（Java）。如何在Spring Boot中解码文件？

这是我在Angular中的代码：（用base64编码文件）在一个带有3个参数（base64、名称、大小）的函数中

readAndUploadFile(theFile: any) {
    let file = new FileModel();
    
    // Set File Information
    file.fileName = theFile.name;
    file.fileSize = theFile.size;
    file.fileType = theFile.type;
    file.lastModifiedTime = theFile.lastModified;
    file.lastModifiedDate = theFile.lastModifiedDate;
    
    // Use FileReader() object to get file to upload
    // NOTE: FileReader only works with newer browsers
    let reader = new FileReader();
    
    // Setup onload event for reader
    reader.onload = () => {
        // Store base64 encoded representation of file
        file.fileAsBase64 = reader.result.toString();
        
        // POST to server
        this.uploadService.uploadFile(file.fileAsBase64,file.fileName,file.fileSize).subscribe(resp => { 
         
            this.messages.push("Upload complete");
            console.log("tst",resp); });
    }
    
    // Read the file
    reader.readAsDataURL(theFile);
} 


uploadFile(): void {
  this.readAndUploadFile(this.theFile);
} 

我在后端的代码：

@RequestMapping("/UploadFile")
public String uploadFile(String base64, String name, String size) throws Exception {
 
    return "true";
}

Answer 1

有一些方法可以对base64进行编码和解码，一个好的方法是使用Apache Commons编解码器库或Java base64编码器/解码器。https://www.baeldung.com/java-base64-encode-and-decode

Answer 2

byte[] data = Base64.decodeBase64(base64);
try (OutputStream stream = new FileOutputStream("path to file ")) {
    stream.write(data);
}

Answer 3

您可以使用以下命令下载转换为Base64格式的文件。

@RequestMapping(value = "/UploadFile")
public String uploadFile(HttpServletResponse response String base64, String name, String size) throws Exception {
    byte[] decodedFile = Base64.getDecoder().decode(base64.getBytes(StandardCharsets.UTF_8));
    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition", "attachment; filename=" + name);
    response.setHeader("Pragma", "no-cache");
    response.setHeader("Cache-Control", "no-cache");

    InputStream is = new ByteArrayInputStream(decodedFile);
    IOUtils.copy(is, response.getOutputStream());
    response.flushBuffer();
    return "true";
}