uk.ac.ceh.components.userstore.UserAttributeReader Maven / Gradle / Ivy

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package uk.ac.ceh.components.userstore;

import java.lang.reflect.Type;
import java.util.Map;

/**
 * The following interface defines how to read given user attributes from a user
 * instance.
 * @author Christopher Johnson
 */
public interface UserAttributeReader {
    /**
     * Returns the map of user attribute keys to their defined Types which this 
     * UserAttributeReader is capable of reading
     * @return the UserAttribute keys which can be read using this reader mapped to
     *  the expected type
     */
    Map getDefinedAttributes();
    
    /**
     * Gets the value of the {@link UserAttribute} represented by uri from the 
     *  user
     * @param user The user to read from
     * @param uri The property to read
     * @return The value of uri from the user if it exists. else null.
     * @throws UserAttributeReaderException if the property exists but could not be read
     */
    Object get(U user, String uri) throws UserAttributeReaderException;
    
    /**
     * The following method will get the specified property off of the given user
     * and attempt to cast that value to the type specified by type.
     * 
     * Implementations are free to attempt to convert the actual value to the specified
     * type if necessary.
     * @param  The type to attempt to get the value of
     * @param user The user to read the property from
     * @param uri The uri of the property to read from the user
     * @param type The class representing the desired type
     * @return The property value to read in the desired type
     * @throws UserAttributeReaderException if the property can not be transformed
     *  to the desired type or the property exists but can not be read
     */
     T get(U user, String uri, Class type) throws UserAttributeReaderException;
}