upload.md

Upload files

Jkmvc uses servlet3.0's javax.servlet.http.Part for uploading files, and improves into a convenient API to handle the upload file.

1 Upload configuration

vim src/main/resources/upload.properties

# upload directory, where the uploaded file save, without postfix "/"
uploadRootDirectory=/var/www/upload
encoding=gbk
# forbidden file extensions, splited by `,`
forbiddenExt = jsp,jspx,exe,sh,php,py
# domain to visit uploaded file
uploadDomain=http://localhost:8081/jkmvc/upload

Configuration item	usage
uploadRootDirectory	The root directory for upload, which jkmvc saves the upload files. To access these files, you need to setup a file server on this diretory.
uploadDomain	Domain name to access to upload files

2 Process upload files

2.1 upload form

The form is defined with enctype =" multipart / form-data " property.

<form class="form-inline" action="<%= req.absoluteUrl("user/uploadAvatar/" + user.getId()) %>" method="post" enctype="multipart/form-data">
    <div class="form-group">
        <label for="avatar">avatar</label>
        <input type="file" class="form-control" id="avatar" placeholder="avatar" name="avatar">
    </div>
    <button type="submit" class="btn btn-default">Upload</button>
</form>

2.2 Receive upload files

/**
 * upload avatar
 */
public fun uploadAvatar()
{
    // find a user
    val id: Int = req["id"]!!
    val user = UserModel(id)
    if(!user.isLoaded()){
        res.renderHtml("use [" + req["id"] + "] not exists")
        return
    }

    // check and handle upload request
    if(req.isUpload){ // check upload request
        user.avatar = req.storePartFileAndGetRelativePath("avatar")
        user.update()
    }

    // redirect to detail page
    redirect("user/detail/$id");
}

3 Download file

After the file upload, it needs to be downloaded. There are 2 ways to download the file:

3.1 Download by java

Call res.render (file: File) in the Controller, to return file to the browser

3.2 Download by the file server

We can use apache / nginx to provide file download service, by specify the upload directory as http root directory

location ~ \.(gif|jpg|jpeg|.js|.css)$ {
    root   /var/www/upload;
    index  index.html index.htm;
}