📦 What is MultipartFile?

MultipartFile is an interface provided by Spring to represent an uploaded file received in a multipart/form-data request.

It allows you to read, store, or manipulate uploaded files in memory or on disk.

🔧 It lives in: org.springframework.web.multipart.MultipartFile

---

🧪 Common Use Case

File upload in a REST API:

✅ Automatically maps uploaded file to the MultipartFile parameter.

---

🎯 Key Methods in MultipartFile

Method	Description
getName()	Returns the name of the parameter in the form
getOriginalFilename()	Gets the original filename (e.g., "resume.pdf")
getContentType()	MIME type like "image/png", "application/pdf"
getBytes()	File content as byte array
getInputStream()	InputStream to read file content
transferTo(File dest)	Save uploaded file to a specific location
isEmpty()	Checks if the file has no content

🛠️ Sample File Upload Endpoint

@RestController
public class FileUploadController {

    @PostMapping("/upload")
    public String uploadFile(@RequestParam("file") MultipartFile file) {
        try {
            File dest = new File("uploads/" + file.getOriginalFilename());
            file.transferTo(dest); // saves file to disk
            return "Uploaded: " + file.getOriginalFilename();
        } catch (IOException e) {
            return "Upload failed: " + e.getMessage();
        }
    }
}

---

📂 Multipart Configuration (Optional)

Spring Boot automatically enables multipart support, but you can configure limits:

---

🧠 Notes

• @RequestParam("file") MultipartFile file binds the form field named "file" to the parameter.
• Can support multiple files using MultipartFile[] or List<MultipartFile>.
• Make sure your frontend uses enctype="multipart/form-data".

---

✅ Summary

Feature	Description
Interface Name	MultipartFile
Used For	Handling file uploads in Spring Boot
Key Methods	getBytes(), getOriginalFilename(), transferTo()
Configuration	Set max sizes in application.properties