src/org/jsecurity/web/tags/PrincipalTag.java

/*
 * Copyright 2005-2008 Jeremy Haile
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jsecurity.web.tags;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspTagException;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.IOException;

/**
 * <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>
 *
 * @since 0.2
 * @author Jeremy Haile
 */
public class PrincipalTag extends SecureTag {

    /*--------------------------------------------
    |             C O N S T A N T S             |
    ============================================*/

    /*--------------------------------------------
    |    I N S T A N C E   V A R I A B L E S    |
    ============================================*/

    /**
     * Commons-logging logger
     */
    protected final transient Log logger = LogFactory.getLog(getClass());

    /**
     * The type of principal to be retrieved, or null if the default principal should be used.
     */
    private String type;

    /**
     * The property name to retrieve of the principal, or null if the <tt>toString()</tt> value should be used.
     */
    private String property;

    /**
     * The default value that should be displayed if the user is not authenticated, or no principal is found.
     */
    private String defaultValue;


    /*--------------------------------------------
    |         C O N S T R U C T O R S           |
    ============================================*/

    /*--------------------------------------------
    |  A C C E S S O R S / M O D I F I E R S    |
    ============================================*/


    public String getType() {
        return type;
    }


    public void setType(String type) {
        this.type = type;
    }


    public String getProperty() {
        return property;
    }


    public void setProperty(String property) {
        this.property = property;
    }


    public String getDefaultValue() {
        return defaultValue;
    }


    public void setDefaultValue(String defaultValue) {
        this.defaultValue = defaultValue;
    }


    /*--------------------------------------------
    |               M E T H O D S               |
    ============================================*/


    @SuppressWarnings({"unchecked"})
    public int onDoStartTag() throws JspException {
        String strValue = null;

        if( getSubject() != null ) {

            // Get the principal to print out
            Object principal;
            
            if( type == null ) {
                principal = getSubject().getPrincipal();
            } else {
                principal = getPrincipalFromClassName();
            }

            // Get the string value of the principal
            if( principal != null ) {
                if( property == null ) {
                    strValue = principal.toString();
                } else {
                    strValue = getPrincipalProperty( principal, property );
                }
            }

        }

        // Print out the principal value if not null
        if( strValue != null ) {
            try {
                pageContext.getOut().write( strValue );
            } catch (IOException e) {
                throw new JspTagException( "Error writing [" + strValue + "] to JSP.", e );
            }
        }

        return SKIP_BODY;
    }

    private Object getPrincipalFromClassName() {
        Object principal = null;
        
        try {
            Class cls = Class.forName(type);
            principal = getSubject().getPrincipals().oneByType( cls );
        } catch (ClassNotFoundException e) {
           if (logger.isErrorEnabled()) {
               logger.error("Unable to find class for name [" + type + "]");
           }
        }
        return principal;
    }


    private String getPrincipalProperty(Object principal, String property) throws JspTagException {
        String strValue = null;

        try {
            BeanInfo bi = Introspector.getBeanInfo( principal.getClass() );

            // Loop through the properties to get the string value of the specified property
            boolean foundProperty = false;
            for( PropertyDescriptor pd : bi.getPropertyDescriptors() ) {
                if( pd.getName().equals( property ) ) {
                    Object value = pd.getReadMethod().invoke( principal, (Object[]) null );
                    strValue = String.valueOf( value );
                    foundProperty = true;
                    break;
                }
            }

            if( !foundProperty ) {
                final String message = "Property [" + property + "] not found in principal of type [" + principal.getClass().getName() + "]";
                if (logger.isErrorEnabled()) {
                    logger.error(message);
                }
                throw new JspTagException( message );
            }

        } catch (Exception e) {
            final String message = "Error reading property [" + property + "] from principal of type [" + principal.getClass().getName() + "]";
            if (logger.isErrorEnabled()) {
                logger.error(message, e);
            }
            throw new JspTagException( message, e );
        }

        return strValue;
    }
}