PrincipalTag.java

package edu.gatech.oad.rocket.findmythings.server.util.tags;

import freemarker.core.Environment;
import freemarker.log.Logger;
import freemarker.template.TemplateDirectiveBody;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModelException;

import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.util.Map;

/**
 * <p>Tag used to print out the String value of a user's default principal,
 * or a specific principal as specified by the tag's attributes.</p>
 *
 * <p> If no attributes are specified, the tag prints out the <tt>toString()</tt>
 * value of the user's default principal.  If the <tt>type</tt> attribute
 * is specified, the tag looks for a principal with the given type.  If the
 * <tt>property</tt> attribute is specified, the tag prints the string value of
 * the specified property of the principal.  If no principal is found or the user
 * is not authenticated, the tag displays nothing unless a <tt>defaultValue</tt>
 * is specified.</p>
 *
 * <p>Equivalent to {@link org.apache.shiro.web.tags.PrincipalTag}</p>
 *
 * @since 0.2
 */
@SuppressWarnings("rawtypes")
class PrincipalTag extends SecureTag {
	private static final Logger log = Logger.getLogger("PrincipalTag");

	/**
	 * The type of principal to be retrieved, or null if the default principal should be used.
	 */
	String getType(Map params) {
		return getParam(params, "type");
	}

	/**
	 * The property name to retrieve of the principal, or null if the <tt>toString()</tt> value should be used.
	 */
	String getProperty(Map params) {
		return getParam(params, "property");
	}

	@Override
	public void render(Environment env, Map params, TemplateDirectiveBody body) throws IOException, TemplateException {
		String result = null;

		if (getSubject() != null) {
			// Get the principal to print out
			Object principal;

			if (getType(params) == null) {
				principal = getSubject().getPrincipal();
			} else {
				principal = getPrincipalFromClassName(params);
			}

			// Get the string value of the principal
			if (principal != null) {
				String property = getProperty(params);

				if (property == null) {
					result = principal.toString();
				} else {
					result = getPrincipalProperty(principal, property);
				}
			}
		}

		// Print out the principal value if not null
		if (result != null) {
			try {
				env.getOut().write(result);
			} catch (IOException ex) {
				throw new TemplateException("Error writing ["+result+"] to Freemarker.", ex, env);
			}
		}
	}

	@SuppressWarnings("unchecked")
	Object getPrincipalFromClassName(Map params) {
		String type = getType(params);

		try {
			Class cls = Class.forName(type);

			return getSubject().getPrincipals().oneByType(cls);
		} catch (ClassNotFoundException ex) {
			log.error("Unable to find class for name ["+type+"]", ex);
		}

		return null;
	}

	String getPrincipalProperty(Object principal, String property) throws TemplateModelException {
		try {
			BeanInfo beanInfo = Introspector.getBeanInfo(principal.getClass());

			// Loop through the properties to get the string value of the specified property
			for (PropertyDescriptor propertyDescriptor : beanInfo.getPropertyDescriptors()) {
				if (propertyDescriptor.getName().equals(property)) {
					Object value = propertyDescriptor.getReadMethod().invoke(principal, (Object[]) null);

					return String.valueOf(value);
				}
			}

			// property not found, throw
			throw new TemplateModelException("Property ["+property+"] not found in principal of type ["+principal.getClass().getName()+"]");
		} catch (Exception ex) {
			throw new TemplateModelException("Error reading property ["+property+"] from principal of type ["+principal.getClass().getName()+"]", ex);
		}
	}
}