在Kotlin中,屬性代理是一種強大的功能,它允許你在不修改原始類的情況下,對類的屬性進行攔截和處理。要實現動態屬性代理,你需要使用KProperty
、Proxy
和InvocationHandler
。下面是一個簡單的示例:
interface MyInterface {
var myProperty: String
get() = "Original value"
set(value) {
println("Setting new value: $value")
}
}
InvocationHandler
接口的類,用于處理屬性訪問:class MyInvocationHandler(private val target: MyInterface) : InvocationHandler {
override fun invoke(proxy: Any?, method: Method, args: Array<out Any?>): Any? {
when (method.name) {
"myProperty" -> {
println("Before getting property")
val value = method.invoke(target, *args) as String
println("After getting property")
return value
}
"myProperty=" -> {
println("Before setting property")
method.invoke(target, *args)
println("After setting property")
return null
}
else -> throw IllegalArgumentException("Unknown method: ${method.name}")
}
}
}
Proxy.newProxyInstance()
方法創建代理對象:val target = MyInterface { "Default value" }
val handler = MyInvocationHandler(target)
val proxy = Proxy.newProxyInstance(
target::class.java.classLoader,
arrayOf<Class<*>>(MyInterface::class.java),
handler
)
println("Getting property: ${proxy.myProperty}") // 輸出:Before getting property
// Original value
proxy.myProperty = "New value" // 輸出:Before setting property
// After setting property
println("Getting property: ${proxy.myProperty}") // 輸出:After getting property
// New value
通過這種方式,你可以實現動態屬性代理,對類的屬性進行攔截和處理,而不需要修改原始類。