001 package edu.nrao.sss.webapp;
002
003 import javax.faces.context.FacesContext;
004 import javax.faces.application.Application;
005 import javax.faces.el.ValueBinding;
006 import javax.faces.el.EvaluationException;
007 import javax.faces.el.ReferenceSyntaxException;
008
009 import org.apache.log4j.Logger;
010
011 /**
012 * This class provides an easy way to get access to JSF Managed Beans via
013 * their EL value bindings (For example "#{managedBean}").
014 * @author btruitt
015 *
016 */
017 public class ManagedBeanRepository {
018 private static final Logger log = Logger.getLogger(ManagedBeanRepository.class);
019
020 /**
021 * Fetches the Object that is currently being used in the FacesContext
022 * by using its JSF Expression Language ValueBinding. The reference returned
023 * is a refrence of type <code>c</code>
024 *
025 * @param c The class of the object being referenced by elStatement
026 * @param elStatement a JSF EL statement (i.e. "#{managedBean}").
027 * @return null if the ValueBinding doesn't exist or is of the wrong type.
028 * @throws IllegalArgumentException if <code>elStatement</code> is invalid.
029 */
030 @SuppressWarnings("unchecked")
031 public static <T> T getManagedBean(Class<T> c, String elStatement)
032 {
033 FacesContext context = FacesContext.getCurrentInstance();
034
035 T ptab = null;
036 if (context != null)
037 {
038 Application app = context.getApplication();
039 if (app != null)
040 {
041 try
042 {
043 ValueBinding vb = app.createValueBinding(elStatement);
044 if (vb != null)
045 {
046 Object value = vb.getValue(context);
047 if (value != null && value.getClass().equals(c))
048 {
049 ptab = (T)value;
050 }
051 }
052 }
053 catch (ReferenceSyntaxException rse)
054 {
055 log.warn("Could not resolve the expression: " + elStatement, rse);
056 throw new IllegalArgumentException("EL statement: " + elStatement +
057 "is invalid", rse);
058 }
059 catch(EvaluationException ee)
060 {
061 log.warn("Could not resolve the expression: " + elStatement, ee);
062 throw new IllegalArgumentException("EL statement: " + elStatement +
063 "is invalid", ee);
064 }
065 }
066 }
067
068 return ptab;
069 }
070 }