@Field
    public void setFileExtension(String fileExtension) {
        this.fileExtension = fileExtension;
    }
If you want to customize the output file's file extension.
Do not include the "."

@param fileExtension
tika-pipes/tika-emitters/tika-emitter-fs/src/main/java/org/apache/tika/pipes/emitter/fs/FileSystemEmitter.java