ninja-core/src/main/java/ninja/utils/MimeTypes.java
public boolean isValidMimeType(String mimeType) {
        if (mimeType == null) {
            return false;
        } else if (mimeType.indexOf(";") != -1) {
            return mimetypes.contains(mimeType.split(";")[0]);
        } else {
            return mimetypes.contains(mimeType);
        }
    }
public boolean isValidMimeType(String mimeType) {
        if (mimeType == null) {
            return false;
        } else if (mimeType.indexOf(";") != -1) {
            return mimetypes.contains(mimeType.split(";")[0]);
        } else {
            return mimetypes.contains(mimeType);
        }
    }
check the mimetype is referenced in the mimetypes database

@param mimeType
the mimeType to verify