I want to Design a simple ETL process where source and output and transformation all three needs to be independent

I want to Design a simple ETL process where source and output and transformation all three needs to be independent i.e source can be a file and output to database and transformation logic must me plugaable. Could any one please help me to design classes where every thing should be dynamic and plugable . ex Extract / input source : read from a file

//future input source can be dbms also

transform : transform file content to capital form.

// this can be easily changeable

Load / output source : put above transform content to a file

/// future output source can be dbms also

Need help in designing classes in java which supports all this. I can use strategy pattern to plug strategy but all three but not able to do it