Introduction
The AOP Interceptor was in EE 6 introduced and was before only supported with additional libraries such as aspectj and jboss-aop.
Before using Interceptor one should first really consider if this is the right tool for solving ones problem. Because using AOP Interceptor is not a holy grail, BUT for certain problem it is. Those are:
- Logging
- Caching
- Security
- And similiar
The above examples are so called cross cutting concern, that are well suited to be solved with AOP Interceptor.
Java EE 6 Interceptors
To create a Java EE Interceptor you create a POJO with:
- A public, no-argument constructor.
- One around-invoke interceptor method with syntax @javax.interceptor.AroundInvoke visibility Object method-name(javax.interceptor.InvocationContext) throws Exception { ... }
Example
public class AuditInterceptor {
private java.util.logging.Logger log = java.util.logging.Logger
.getLogger(AuditInterceptor.class.getName());
@javax.interceptor.AroundInvoke
protected Object invoke(javax.interceptor.InvocationContext ctx)
throws Exception {
StringBuilder sb = new StringBuilder("[");
for (Object obj : ctx.getParameters()) {
sb.append(obj.toString());
sb.append(", ");
}
sb.append("]");
log.log(java.util.logging.Level.INFO,
"user {0} invoced {1} with method {2} and parameters: {3}",
new Object[] { ctx.getTarget().toString(),
ctx.getMethod().getName(), sb.toString() });
return ctx.proceed();
}
}
To use it, add @javax.interceptor.Interceptors(AuditInterceptor.class) to any bean that supports injection, e.g. Servlet, JSF ManagedBean, EJB.
Example
@javax.interceptor.Interceptors(AuditInterceptor.class)
@javax.ejb.Stateless
public class FooSLSB {
public void save(Object obj) {
// do something
}
}
NOTE: You can either annotate the class (Interceptor will be called whenever every public method is called) or a specific method.
The final piece to make it work is to add the beans.xml in:
- META-INF/ for ejb jar.
- WEB-INF/ for web war.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/beans_1_0.xsd">
</beans>
