我嘗試爲Java字節碼實現幾個靜態分析。他們試圖計算某種方法是否具有特定屬性,例如是一種工廠方法。由於這些分析很難測試,因此我決定編寫一些Java代碼並直接使用正確的屬性註釋這些方法。運行分析後,很容易自動檢查計算值和註釋屬性是否相同。Java註釋的默認值是否編譯爲字節碼?
MyAnnotation:
@Retention(RUNTIME)
@Target(METHOD)
public @interface FactoryMethodProperty {
FactoryMethodKeys value() default FactoryMethodKeys.NonFactoryMethod;
}
實例測試代碼:
public class PublicFactoryMethod {
private PublicFactoryMethod(){
// I'm private
}
@FactoryMethodProperty
public static void newInstanceAfterOtherConstructorCall(){
new TransFacoryMethod();
new PublicFactoryMethod();
}
@FactoryMethodProperty(FactoryMethodKeys.IsFactoryMethod)
public static PublicFactoryMethod newInstance(){
return new PublicFactoryMethod();
}
}
因爲大部分的在我的測試代碼的方法是沒有工廠的方法,我默認值設置爲枚舉值「FactoryMethodKeys.NonFactoryMethod 」。但是,當我沒有明確地將枚舉值傳遞給註釋時,它不會被編譯爲字節碼。
字節碼:
#23 = Utf8 value
#24 = Utf8 Lorg/opalj/fpa/test/annotations/FactoryMethodKeys;
#25 = Utf8 IsFactoryMethod
{
public static void newInstanceAfterOtherConstructorCall();
descriptor:()V
flags: ACC_PUBLIC, ACC_STATIC
RuntimeVisibleAnnotations:
0: #16()
Code:
stack=1, locals=0, args_size=0
0: new #17 // class factoryMethodTest/TransFacoryMethod
3: invokespecial #19 // Method factoryMethodTest/TransFacoryMethod."<init>":()V
6: new #1 // class factoryMethodTest/PublicFactoryMethod
9: invokespecial #20 // Method "<init>":()V
12: return
LineNumberTable:
line 49: 0
line 50: 6
line 51: 12
LocalVariableTable:
Start Length Slot Name Signature
public static factoryMethodTest.PublicFactoryMethod newInstance();
descriptor:()LfactoryMethodTest/PublicFactoryMethod;
flags: ACC_PUBLIC, ACC_STATIC
RuntimeVisibleAnnotations:
0: #16(#23=e#24.#25)
Code:
stack=2, locals=0, args_size=0
0: new #1 // class factoryMethodTest/PublicFactoryMethod
3: dup
4: invokespecial #20 // Method "<init>":()V
7: areturn
LineNumberTable:
line 55: 0
LocalVariableTable:
Start Length Slot Name Signature
}
我是怎麼了?爲什麼默認值完全被忽略?