java.naming异常

javax.naming.NameNotFoundException: 名前 jdbc はこのコンテキストにバインドされていません    at org.apache.naming.NamingContext.lookup(NamingContext.java:770)    at org.apache.naming.NamingContext.lookup(NamingContext.java:140)    at org.apache.naming.NamingContext.lookup(NamingContext.java:781)    at org.apache.naming.NamingContext.lookup(NamingContext.java:140)    at org.apache.naming.NamingContext.lookup(NamingContext.java:781)    at org.apache.naming.NamingContext.lookup(NamingContext.java:153)    at org.apache.naming.SelectorContext.lookup(SelectorContext.java:152)    at javax.naming.InitialContext.lookup(Unknown Source)    at com.sys.util.Struts.<init>(Struts.java:14)    at com.sys.model.Product.<init>(Product.java:12)    at com.sys.action.SaveProductAction.execute(SaveProductAction.java:17)    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:877)    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:594)    at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1675)    at java.lang.Thread.run(Unknown Source)

public class Struts {    protected Context ctx = new InitialContext();    protected DataSource ds;    protected Connection conn;        public Struts() throws Exception {        ds = (DataSource)ctx.lookup("java:/comp/env/jdbc/struts");        conn = ds.getConnection();    }}