54.3 The interceptor Example Application

The interceptor example demonstrates how to use an interceptor class, containing an @AroundInvoke interceptor method, with a stateless session bean.

The HelloBean stateless session bean is a simple enterprise bean with two business methods, getName and setName, to retrieve and modify a string. The setName business method has an @Interceptors annotation that specifies an interceptor class, HelloInterceptor, for that method:

@Interceptors(HelloInterceptor.class)
public void setName(String name) {
    this.name = name;
}

The HelloInterceptor class defines an @AroundInvoke interceptor method, modifyGreeting, that converts the string passed to HelloBean.setName to lowercase:

@AroundInvoke
public Object modifyGreeting(InvocationContext ctx) throws Exception {
    Object[] parameters = ctx.getParameters();
    String param = (String) parameters[0];
    param = param.toLowerCase();
    parameters[0] = param;
    ctx.setParameters(parameters);
    try {
        return ctx.proceed();
    } catch (Exception e) {
        logger.warning("Error calling ctx.proceed in modifyGreeting()");
        return null;
    }
}

The parameters to HelloBean.setName are retrieved and stored in an Object array by calling the InvocationContext.getParameters method. Because setName only has one parameter, it is the first and only element in the array. The string is set to lowercase and stored in the parameters array, then passed to InvocationContext.setParameters. To return control to the session bean, InvocationContext.proceed is called.

The user interface of interceptor is a JavaServer Faces web application that consists of two Facelets views: index.xhtml, which contains a form for entering the name, and response.xhtml, which displays the final name.