I have a osm map for a certain region. Also using osm2po I extracted the graph which includes edges and nodes into the database. Now I want to visualize the map and then visualize the shortest path. How can I visualize the map in QGIS first? I mean it doesn't directly take the osm file? How can I accomplish this?
Try the OpenStreetMap Python plugin that ships with QGIS.
Choose the Plugins-> Manage Plugins... menu and enable the plugin.
Next, read the new HTML manual on using the plugin:
OpenStreetMap Plugin — QGIS User Guide
When you are ready to start doing some path routing check out underdark's info on the subject:
Tagged posts: osm2po | Free and Open Source GIS Ramblings
Starting with: An osm2po Quickstart