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package javax.interceptor;

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

/**
 * <p>Exposes context information about the intercepted invocation and operations 
 * that enable interceptor methods to control the behavior of the invocation chain.</p>
 * 
 * <pre>
 *
 *    &#064;AroundInvoke
 *    public Object logInvocation(InvocationContext ctx) throws Exception {
 *       String class = ctx.getMethod().getDeclaringClass().getName();
 *       String method = ctx.getMethod().getName();
 *       Logger.global.entering(class, method, ctx.getParameters());
 *       try {
 *          Object result = ctx.proceed();
 *          Logger.global.exiting(class, method, result);
 *          return result;
 *       }
 *       catch (Exception e) {
 *          Logger.global.throwing(class, method, e);
 *          throw e;
 *       }
 *
 *    }
 * 
 * </pre>
 *
 * @since Interceptors 1.0
 */
public interface InvocationContext {

    /**
     * Returns the target instance.
     * 
     * @return the target instance
     */
    public Object getTarget();

    /**
     * Returns the timer object associated with a timeout
     * method invocation on the target class, or a null value for method
     * and lifecycle callback interceptor methods.  For example, when associated
     * with an EJB component timeout, this method returns {@link javax.ejb.Timer}
     * 
     * @return the timer object or a null value
     *
     * @since Interceptors 1.1
     */
    public Object getTimer();

    /**
     * Returns the method of the target class for which the interceptor
     * was invoked.  For method interceptors, the method of the 
     * target class is returned. For lifecycle callback interceptors, 
     * a null value is returned.
     * 
     * @return the method, or a null value
     */
    public Method getMethod();

    /**
     * Returns the parameter values that will be passed to the method of
     * the target class. If {@code setParameters()} has been called,
     * {@code getParameters()} returns the values to which the parameters 
     * have been set.  
     * 
     * @return the parameter values, as an array
     * 
     * @exception java.lang.IllegalStateException if invoked within
     * a lifecycle callback method.
     */
    public Object[] getParameters();
    
    /**
     * Sets the parameter values that will be passed to the method of the 
     * target class.  
     *
     * @exception java.lang.IllegalStateException if invoked within
     * a lifecycle callback method.
     *
     * @exception java.lang.IllegalArgumentException if the types of the 
     * given parameter values do not match the types of the method parameters, 
     * or if the number of parameters supplied does not equal the number of 
     * method parameters.
     * 
     * @param params the parameter values, as an array
     */
    public void setParameters(Object[] params);

    /**
     * Returns the context data associated with this invocation or
     * lifecycle callback.  If there is no context data, an
     * empty {@code Map<String,Object>} object will be returned.
     * 
     * @return the context data, as a map
     */
    public Map<String, Object> getContextData();

    /**
     * Proceed to the next interceptor in the interceptor chain.
     * Return the result of the next method invoked, or a null 
     * value if the method has return type void.
     * 
     * @return the return value of the next method in the chain
     */
    public Object proceed() throws Exception;

}