It replaced the JBCL interface that were used in JDeveloper V1 and V2. JSPs are normal HTML pages with Java code pieces embedded in them. A JSP compiler is used in the background to generate a Servlet from the JSP page. Obviously your web server need to support JSP pages and must be configured properly to handle them. The class file is then executed on the server.
Output produced by the servlet is returned to the web browser.
Output will typically be HTML or XML code. You can use Oracle JDeveloper to create JSP pages. Alternatively you can open a standard text file and code the required HTML and Java manually. Java Stored procedures are executed by the database JVM in database memory space. Please note that Java Stored procedures are by default executed with invokers rights.