Java APIs

I am using Weblogic81+Eclipse3.1+myEclipse3.64+J2SE142_08 to test a very simple web app with only one java file DVDManager.java and one index.jsp file. I imported java class and tried to it in jsp:
...
<jsp:useBean id="dvdmanager" scope="session" class="DVDManager" />
...
then I built the project without problem, but after I deployed the web app, and tried to run http://http://localhost:7001/DVDManager/, I got the following error:

<Error> <HTTP> <BEA-101020> <[ServletContext(id=12863780,name=DVDManager,context-path=/DVDManager)] Servlet failed with Exception
weblogic.servlet.jsp.JspException: (line 5): class 'DVDManager' could not be loaded
at weblogic.servlet.jsp.JspLexer.jspException(JspLexer.java:712)
at weblogic.servlet.jsp.JspLexer.processBeanTag(JspLexer.java:1380)

I also found that, if I don't use <jsp: useBean .../> and try to create a DVDManager object in index.jsp, I got the following error:

C:\bea\user_projects\domains\mydomain\.\myserver\.wlnotdelete\extract\myserver_dvdmanager_WebRoot\jsp_servlet\__index.java:137: cannot access DVDManager
bad class file: D:\EclipseWorkspace\DVDManager\WebRoot\WEB-INF\classes\DVDManager.class
class file has wrong version 49.0, should be 48.0
Please remove or make sure it appears in the correct subdirectory of the classpath.
DVDManager m = new DVDManager(); //[ /index.jsp; Line: 9]

the java home and classpath is correct. Anyone can help please? thanks.