How to convert a multipart file to File?

问题:

Can any one tell me what is a the best way to convert a multipart file (org.springframework.web.multipart.MultipartFile) to File (java.io.File) ?

In my spring mvc web project i'm getting uploaded file as Multipart file.I have to convert it to a File(io) ,there fore I can call this image storing service(Cloudinary).They only take type (File).

I have done so many searches but failed.If anybody knows a good standard way please let me know? Thnx

回答1:

You can get the content of multipartFile by using the getBytes method and you can create an instance of the File class by using the FileOutputStream class.

public File convert(MultipartFile file)
{    
    File convFile = new File(file.getOriginalFilename());
    convFile.createNewFile(); 
    FileOutputStream fos = new FileOutputStream(convFile); 
    fos.write(file.getBytes());
    fos.close(); 
    return convFile;
}

You can also use the transferTo method:

public File multipartToFile(MultipartFile multipart) throws IllegalStateException, IOException 
{
    File convFile = new File( multipart.getOriginalFilename());
    multipart.transferTo(convFile);
    return convFile;
}

回答2:

Although the accepted answer is correct but if you are just trying to upload your image to cloudinary, there's a better way:

Map upload = cloudinary.uploader().upload(multipartFile.getBytes(), ObjectUtils.emptyMap());

Where multipartFile is your org.springframework.web.multipart.MultipartFile.

回答3:

small correction on @PetrosTsialiamanis post , new File( multipart.getOriginalFilename()) this will create file in server location where sometime you will face write permission issues for the user, its not always possible to give write permission to every user who perform action. System.getProperty("java.io.tmpdir") will create temp directory where your file will be created properly. This way you are creating temp folder, where file gets created , later on you can delete file or temp folder.

public  static File multipartToFile(MultipartFile multipart, String fileName) throws IllegalStateException, IOException {
    File convFile = new File(System.getProperty("java.io.tmpdir")+"/"+fileName);
    multipart.transferTo(convFile);
    return convFile;
}

put this method in ur common utility and use it like for eg. Utility.multipartToFile(...)

回答4:

You can also use the Apache Commons IO library and the FileUtils class. In case you are using maven you can load it using the above dependency.

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.4</version>
</dependency>

The source for the MultipartFile save to disk.

File file = new File(directory, filename);

// Create the file using the touch method of the FileUtils class.
// FileUtils.touch(file);

// Write bytes from the multipart file to disk.
FileUtils.writeByteArrayToFile(file, multipartFile.getBytes());

回答5:

The answer by Alex78191 has worked for me.

public File getTempFile(MultipartFile multipartFile)
{

CommonsMultipartFile commonsMultipartFile = (CommonsMultipartFile) multipartFile;
FileItem fileItem = commonsMultipartFile.getFileItem();
DiskFileItem diskFileItem = (DiskFileItem) fileItem;
String absPath = diskFileItem.getStoreLocation().getAbsolutePath();
File file = new File(absPath);

//trick to implicitly save on disk small files (<10240 bytes by default)

if (!file.exists()) {
    file.createNewFile();
    multipartFile.transferTo(file);
}

return file;
}

For uploading files having size greater than 10240 bytes please change the maxInMemorySize in multipartResolver to 1MB.

<bean id="multipartResolver"
    class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- setting maximum upload size t 20MB -->
<property name="maxUploadSize" value="20971520" />
<!-- max size of file in memory (in bytes) -->
<property name="maxInMemorySize" value="1048576" />
<!-- 1MB --> </bean>

回答6:

You can access tempfile in Spring by casting if the class of interface MultipartFile is CommonsMultipartFile.

public File getTempFile(MultipartFile multipartFile)
{
    CommonsMultipartFile commonsMultipartFile = (CommonsMultipartFile) multipartFile;
    FileItem fileItem = commonsMultipartFile.getFileItem();
    DiskFileItem diskFileItem = (DiskFileItem) fileItem;
    String absPath = diskFileItem.getStoreLocation().getAbsolutePath();
    File file = new File(absPath);

    //trick to implicitly save on disk small files (<10240 bytes by default)
    if (!file.exists()) {
        file.createNewFile();
        multipartFile.transferTo(file);
    }

    return file;
}

To get rid of the trick with files less than 10240 bytes maxInMemorySize property can be set to 0 in @Configuration @EnableWebMvc class. After that, all uploaded files will be stored on disk.

@Bean(name = "multipartResolver")
    public CommonsMultipartResolver createMultipartResolver() {
        CommonsMultipartResolver resolver = new CommonsMultipartResolver();
        resolver.setDefaultEncoding("utf-8");
        resolver.setMaxInMemorySize(0);
        return resolver;
    }

回答7:

  private File convertMultiPartToFile(MultipartFile file ) throws IOException
    {
        File convFile = new File( file.getOriginalFilename() );
        FileOutputStream fos = new FileOutputStream( convFile );
        fos.write( file.getBytes() );
        fos.close();
        return convFile;
    }