Forge model conversion, transparent png pictures can not be converted, java language

1. The original code is convertible
2. Now there is a problem with the conversion of transparent png images, and there is no error, but the status code at the time of download is 404, and there is no problem with opaque png and jpg images
3. Next, the name of the picture, originally .png, the browser reported an error _ png.jpg and * _ png.jpg.png image could not be found
does anyone know why or how to solve it?

Apr.17,2021
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e53b3f-45263.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e53b3f-45263.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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