html5 file轉換base64

html中file

  <tr>
                                <td>註冊文件</td>
                                <td colspan="3"><input id="file"  type="file" name="file" autocomplete="off"/><input  type="hidden" name="registerBase64" autocomplete="off"/></td>
                            </tr>

javascript處理

$("#file").change(function() {
        var file = this.files[0];
        if(file.size>1024*1024*0.3){
        toastr.warning('上傳文件太大！');
            return false;
        }
        var reader = new FileReader();
        reader.readAsDataURL(file);
        reader.onload = function(f) {
        
        var res=this.result.replace("data:application/octet-stream;base64,", "");
            $("input[name='registerBase64']").val(res);
        }
    });

後臺action獲取

private String registerBase64;
    public String getRegisterBase64() {
        return registerBase64;
    }

    public void setRegisterBase64(String registerBase64) {
        this.registerBase64 = registerBase64;
    }