Runtime Proxies

The runtime side of ProxyBuilder is one class: DynamicProxyBuilder. You give it an interface and an instance; you chain on the behaviour you want; you call .build() and receive a proxy that you can hand to any consumer of the interface.

What you can add to a runtime proxy

• Pre-actions — run before every method invocation.
• Post-actions — run after every method invocation.
• Security rules — return false to refuse the call.
• Metrics — record method timings through Dropwizard Metrics.
• Logging — print invocation details through the project logger.
• Virtual proxy strategy — lazily create the wrapped instance only when needed.

Each is a single builder call. You can combine as many as you need on the same proxy.

A minimal example

Service proxy = DynamicProxyBuilder
    .createBuilder(Service.class, new ServiceImpl())
    .addIPreAction((original, method, args) -> { /* before */ })
    .addIPostAction((original, method, args) -> { /* after */ })
    .build();

The first argument to createBuilder is the interface type. The second is the real implementation that the proxy will delegate to. Everything else is optional.

What you do not do

• You do not need a classpath scanner. The proxy is created for one instance, in one place.
• You do not need a special runtime container. JDK dynamic proxies use a class loader you control.
• You do not need pointcut expressions. The hooks apply to every method on the interface.

Next steps

Read the page for each builder feature you want to use. Each one is small and self-contained.