package com.panogenesis.webapp.taglib;
   
   import java.lang.reflect.AccessibleObject;
   import java.lang.reflect.Field;
   import java.util.HashMap;
   import java.util.Map;
   
   import javax.servlet.jsp.JspException;
   import javax.servlet.jsp.PageContext;
  import javax.servlet.jsp.tagext.TagSupport;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import com.panogenesis.Constants;
  
  
  /***
   * <p>This class is designed to put all the public variables in a class to a
   * specified scope - designed for exposing a Constants class to Tag
   * Libraries.</p>
   *
   * <p>It is designed to be used as follows:
   * <pre>&lt;tag:constants /&gt;</pre>
   * </p>
   *
   * <p>Optional values are "className" (fully qualified) and "scope".</p>
   *
   * <p>
   * <a href="BaseAction.java.html"><i>View Source</i></a>
   * </p>
   *
   * @author <a href="mailto:matt@raibledesigns.com">Matt Raible</a>
   * @version $Revision: 1.5 $ $Date: 2004/09/30 04:41:19 $
   *
   * @jsp.tag name="constants" bodycontent="empty"
   *  tei-class="com.panogenesis.webapp.taglib.ConstantsTei"
   */
  public class ConstantsTag extends TagSupport {
      private final Log log = LogFactory.getLog(ConstantsTag.class);
      
      /***
       * The class to expose the variables from.
       */
      public String clazz = Constants.class.getName();
  
      /***
       * The scope to be put the variable in.
       */
      protected String scope = null;
  
      /***
       * The single variable to expose.
       */
      protected String var = null;
  
      public int doStartTag() throws JspException {
          // Using reflection, get the available field names in the class
          Class c = null;
          int toScope = PageContext.PAGE_SCOPE;
  
          if (scope != null) {
              toScope = getScope(scope);
          }
  
          try {
              c = Class.forName(clazz);
          } catch (ClassNotFoundException cnf) {
              log.error("ClassNotFound - maybe a typo?");
              throw new JspException(cnf.getMessage());
          }
  
          try {
              // if var is null, expose all variables
              if (var == null) {
                  Field[] fields = c.getDeclaredFields();
  
                  AccessibleObject.setAccessible(fields, true);
  
                  for (int i = 0; i < fields.length; i++) {
                      /*if (log.isDebugEnabled()) {
                         log.debug("putting '" + fields[i].getName() + "=" +
                                   fields[i].get(this) + "' into " + scope +
                                   " scope");
                         }*/
                      pageContext.setAttribute(fields[i].getName(),
                                               fields[i].get(this), toScope);
                  }
              } else {
                  try {
                      String value = (String) c.getField(var).get(this);
                      pageContext.setAttribute(c.getField(var).getName(), value,
                                               toScope);
                  } catch (NoSuchFieldException nsf) {
                      log.error(nsf.getMessage());
                      throw new JspException(nsf);
                  }
              }
          } catch (IllegalAccessException iae) {
              log.error("Illegal Access Exception - maybe a classloader issue?");
             throw new JspException(iae);
         }
 
         // Continue processing this page
         return (SKIP_BODY);
     }
 
     /***
      * @jsp.attribute
      */
     public void setClassName(String clazz) {
         this.clazz = clazz;
     }
 
     public String getClassName() {
         return this.clazz;
     }
 
     /***
      * @jsp.attribute
      */
     public void setScope(String scope) {
         this.scope = scope;
     }
 
     public String getScope() {
         return (this.scope);
     }
 
     /***
      * @jsp.attribute
      */
     public void setVar(String var) {
         this.var = var;
     }
 
     public String getVar() {
         return (this.var);
     }
 
     /***
      * Release all allocated resources.
      */
     public void release() {
         super.release();
         clazz = null;
         scope = Constants.class.getName();
     }
     
     // ~========== From Struts' TagUtils class =====================
 
     /***
      * Maps lowercase JSP scope names to their PageContext integer constant
      * values.
      */
     private static final Map scopes = new HashMap();
 
     /***
      * Initialize the scope names map and the encode variable with the 
      * Java 1.4 method if available.
      */
     static {
         scopes.put("page", new Integer(PageContext.PAGE_SCOPE));
         scopes.put("request", new Integer(PageContext.REQUEST_SCOPE));
         scopes.put("session", new Integer(PageContext.SESSION_SCOPE));
         scopes.put("application", new Integer(PageContext.APPLICATION_SCOPE));
     }
     
     /***
      * Converts the scope name into its corresponding PageContext constant value.
      * @param scopeName Can be "page", "request", "session", or "application" in any
      * case.
      * @return The constant representing the scope (ie. PageContext.REQUEST_SCOPE).
      * @throws JspException if the scopeName is not a valid name.
      */
     public int getScope(String scopeName) throws JspException {
         Integer scope = (Integer) scopes.get(scopeName.toLowerCase());
 
         if (scope == null) {
             throw new JspException("Scope '" + scopeName + "' not a valid option");
         }
 
         return scope.intValue();
     }
 }