This JavaPro article says you should learn;
- HyperText Markup Language (HTML)
- Servlets and JSP
- JavaScript
- Structured Query Language (SQL) and Java Database Connectivity (JDBC)
- Web Container Administration and Application Deployment
- eXtensible Markup Language (XML)
- Model 2 Architecture, JSP Standard Tag Libraries (JSTL)
- Jakarta Taglibs Project and Other Libraries, Apache’s Struts Project,
- EXtensible HyperText Markup Language (XHTML)
- Dynamic HTML (DHTML)
- Applet Programming
- The HTTP Protocol
- Enterprise JavaBeans (EJB)
- Java Naming and Directory Interface (JNDI)