使用java反射操作類的建構函式,成員變數和成員方法
阿新 • • 發佈:2019-01-03
在java.lang.reflect包中有三個類Field,Method,Constructor.分別描述域,方法,構造器。參考API,關於這三個類的說明。
在執行時使用反射分析物件,如果訪問的是私有域或是私有方法,私有建構函式,會丟擲IllegalAccessException.因為反射機制的預設行為受限於java的訪問控制,然而,如果一個java程式沒有受到安全管理器的控制,就可以覆蓋訪問控制。為了達到這個目的,需要呼叫Field,Method,Constructor物件的setAccessible方法,setAccessible方法是AccessibleObject類的一個方法,是Field,Method,Constructor類的公共超類。
setAccessible(true);
不要過多地使用反射:破壞類封裝;效率偏低;編譯器不容易幫助發現錯誤,在執行時才會被發現。
我使用反射,是為了寫單元測試程式碼,對執行物件的分析,改變物件的私有域等,達到測試需要的覆蓋率。
以下提供程式碼事例:
測試類:
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