I want to use custom Boot-loader using internal flash.Is there any example source code of boot-loader and Application source?

[VGoya]

I am working on STM32L071CB

Want to divide internal flash in 3 parts

1. for boot-loader code

2. for Application code

3. for storing Image received on UART for Upgrade Application Source

Please Provide example source code.

[Tesla DeLorean]

You should look for ST's IAP (In Application Programming) examples in the HAL repositories for the part and similar boards. Likely also App Notes on topic area.​