如何在Sencha中实现文件上传和下载？

Ext.create('Ext.form.Panel', {
    fullscreen: true,
    items: [
        {
            xtype: 'filefield',
            name: 'photo',
            label: '选择照片'
        },
        {
            xtype: 'button',
            text: '上传',
            handler: function() {
                var form = this.up('formpanel');
                form.submit({
                    url: 'upload.php',
                    success: function(form, response) {
                        console.log('上传成功');
                    },
                    failure: function(form, response) {
                        console.log('上传失败');
                    }
                });
            }
        }
    ]
});

Ext.create('Ext.Button', {
    text: '下载文件',
    handler: function() {
        window.open('download.php?file=file.pdf', '_system');
    }
});