MyInterceptor.java

package org.javaee7.interceptor.aroundconstruct;

import javax.interceptor.AroundConstruct;
import javax.interceptor.Interceptor;
import javax.interceptor.InvocationContext;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

/**
 * @author Radim Hanus
 */
@Interceptor
@MyInterceptorBinding
public class MyInterceptor {
	@AroundConstruct
	public Object onConstruct(InvocationContext context) throws Exception {
		// null before the InvocationContext.proceed() returns
		Object target = context.getTarget();
		isNull(target);
		// null in case of AroundConstruct
		Method method = context.getMethod();
		isNull(method);
		// NOT null in case of AroundConstruct
		Constructor ctor = context.getConstructor();
		isNotNull(ctor);

		// perform the constructor injection
		Object result = context.proceed();
		isNull(result);

		// NOT null after the InvocationContext.proceed() completes
		target = context.getTarget();
		isNotNull(target);
		// a constructor should have been called
		GreetingBean bean = (GreetingBean) target;
		isBoolean(bean.isConstructed(), true);
		isBoolean(bean.isInitialized(), false);
		// constructor injection should have been done
		isNotNull(bean.getParam());

		return null;
	}

	private static void isNull(Object o) throws Exception {
		if (o != null) {
			throw new IllegalStateException("null required");
		}
	}

	private static void isNotNull(Object o) throws Exception {
		if (o == null) {
			throw new IllegalStateException("not null required");
		}
	}

	private static void isBoolean(Object o, Boolean value) {
		if (!o.equals(value)) {
			throw new IllegalStateException(value + " required");
		}
	}
}