Question: How to export Oracle DB data using SQL Developer? I need all data, tables, constraints, structure and so on.

Answer: 
In SQL Developer, from the top menu choose Tools > Data Export. This launches the Data Export wizard. It's pretty straightforward from there. 

There is a tutorial on the OTN site. [Find it here](http://www.oracle.com/webfolder/technetwork/tutorials/obe/db/sqldev/r30/SQLdev3.0_Import_Export/sqldev3.0_import_export.htm).
In **version 3**, they changed "**export**" to "**unload**". It still functions more or less the same.