[JBoss Seam] - NullPointerException when get a row from a list
by dago
here is a class
package book;
import static javax.ejb.TransactionAttributeType.REQUIRES_NEW;
import static org.jboss.seam.ScopeType.SESSION;
import java.io.Serializable;
import java.util.List;
import javax.ejb.Remove;
import javax.ejb.Stateful;
import javax.ejb.TransactionAttribute;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.jboss.seam.ScopeType;
import org.jboss.seam.annotations.Logger;
import org.jboss.seam.annotations.Destroy;
import org.jboss.seam.annotations.Factory;
import org.jboss.seam.annotations.In;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.Observer;
import org.jboss.seam.annotations.Out;
import org.jboss.seam.annotations.Scope;
import org.jboss.seam.annotations.datamodel.DataModel;
import org.jboss.seam.annotations.datamodel.DataModelSelection;
import org.jboss.seam.core.FacesMessages;
import org.jboss.seam.log.Log;
@Stateful
@Scope(ScopeType.SESSION)
@LoggedIn
@Name("cnMessageActionTest")
public class CnMessageActionTest implements CnMessageTestInterface
{
@PersistenceContext
private EntityManager em;
@DataModel
private List cnMessages;
//@Out(required=false)
//@PersistenceContext
private CnMessage cnMessage;
@Factory
//@Observer("CnMessage hello")
public void getCnMessages()
{
cnMessages = em.createQuery("from CnMessage").getResultList();
//cnMessage = cnMessages.get(0);
}
public void getCnMessage(String enMsg){
cnMessage = cnMessages.get(1);
//return "#{cnMessages.cnMsg}";
}
@Destroy @Remove
public void destroy()
{}
}
when i call the method "getCnMessage" from another class
public class UITicker extends UIOutput {
private CnMessageActionTest cmat;
public void encodeBegin(FacesContext ctx) throws IOException {
ResponseWriter writer = ctx.getResponseWriter();
writer.startElement("div", this);
String enMsg = (String)getAttributes().get("enMsg");
cmat = new CnMessageActionTest();
cmat.getCnMessage(enMsg);
if (enMsg!=null)
writer.writeAttribute("enMsg", enMsg, null);
String style = (String)getAttributes().get("style");
if (style!=null)
writer.writeAttribute("style", style, null);
String styleClass = (String)getAttributes().get("styleClass");
if (styleClass!=null)
writer.writeAttribute("class", styleClass, null);
}
public void encodeEnd(FacesContext context) throws IOException {
ResponseWriter writer = context.getResponseWriter();
writer.endElement("div");
}
}
it thow exception:
java.lang.NullPointerException
at book.CnMessageActionTest.getCnMessage(CnMessageActionTest.java:60)
at ticker.UITicker.encodeBegin(UITicker.java:55)
at com.sun.facelets.tag.jsf.ComponentSupport.encodeRecursive(ComponentSupport.java:232)
at com.sun.facelets.tag.jsf.ComponentSupport.encodeRecursive(ComponentSupport.java:239)
at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:554)
at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:352)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at book.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:42)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.jboss.seam.servlet.SeamRedirectFilter.doFilter(SeamRedirectFilter.java:30)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
at java.lang.Thread.run(Thread.java:619)
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19Â years, 2Â months