Jeśli mam dwie następujące klasy:Dlaczego środowisko Java 8 stosuje adnotacje w sposób odmienny do klas pochodnych?
// Base.java
public abstract class Base<T> {
abstract void method(T t);
}
i
// Derived.java
public class Derived extends Base<Number> {
@Deprecated
void method(Number n) {}
}
I następnie skompilować je javac Base.java Derived.java
a następnie użyć javap -v Derived
. Jeśli używam Java 7, mam
public class Derived extends Base<java.lang.Number>
Signature: #17 // LBase<Ljava/lang/Number;>;
SourceFile: "Derived.java"
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #5.#20 // Base."<init>":()V
#2 = Class #21 // java/lang/Number
#3 = Methodref #4.#22 // Derived.method:(Ljava/lang/Number;)V
#4 = Class #23 // Derived
#5 = Class #24 // Base
#6 = Utf8 <init>
#7 = Utf8 ()V
#8 = Utf8 Code
#9 = Utf8 LineNumberTable
#10 = Utf8 method
#11 = Utf8 (Ljava/lang/Number;)V
#12 = Utf8 Deprecated
#13 = Utf8 RuntimeVisibleAnnotations
#14 = Utf8 Ljava/lang/Deprecated;
#15 = Utf8 (Ljava/lang/Object;)V
#16 = Utf8 Signature
#17 = Utf8 LBase<Ljava/lang/Number;>;
#18 = Utf8 SourceFile
#19 = Utf8 Derived.java
#20 = NameAndType #6:#7 // "<init>":()V
#21 = Utf8 java/lang/Number
#22 = NameAndType #10:#11 // method:(Ljava/lang/Number;)V
#23 = Utf8 Derived
#24 = Utf8 Base
{
public Derived();
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method Base."<init>":()V
4: return
LineNumberTable:
line 1: 0
void method(java.lang.Number);
flags:
Code:
stack=0, locals=2, args_size=2
0: return
LineNumberTable:
line 7: 0
Deprecated: true
RuntimeVisibleAnnotations:
0: #14()
void method(java.lang.Object);
flags: ACC_BRIDGE, ACC_SYNTHETIC
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: aload_1
2: checkcast #2 // class java/lang/Number
5: invokevirtual #3 // Method method:(Ljava/lang/Number;)V
8: return
LineNumberTable:
line 1: 0
}
jeśli robię to samo z Java 8, I zamiast dostać
public class Derived extends Base<java.lang.Number>
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #5.#20 // Base."<init>":()V
#2 = Class #21 // java/lang/Number
#3 = Methodref #4.#22 // Derived.method:(Ljava/lang/Number;)V
#4 = Class #23 // Derived
#5 = Class #24 // Base
#6 = Utf8 <init>
#7 = Utf8 ()V
#8 = Utf8 Code
#9 = Utf8 LineNumberTable
#10 = Utf8 method
#11 = Utf8 (Ljava/lang/Number;)V
#12 = Utf8 Deprecated
#13 = Utf8 RuntimeVisibleAnnotations
#14 = Utf8 Ljava/lang/Deprecated;
#15 = Utf8 (Ljava/lang/Object;)V
#16 = Utf8 Signature
#17 = Utf8 LBase<Ljava/lang/Number;>;
#18 = Utf8 SourceFile
#19 = Utf8 Derived.java
#20 = NameAndType #6:#7 // "<init>":()V
#21 = Utf8 java/lang/Number
#22 = NameAndType #10:#11 // method:(Ljava/lang/Number;)V
#23 = Utf8 Derived
#24 = Utf8 Base
{
public Derived();
descriptor:()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method Base."<init>":()V
4: return
LineNumberTable:
line 1: 0
void method(java.lang.Number);
descriptor: (Ljava/lang/Number;)V
flags:
Code:
stack=0, locals=2, args_size=2
0: return
LineNumberTable:
line 5: 0
Deprecated: true
RuntimeVisibleAnnotations:
0: #14()
void method(java.lang.Object);
descriptor: (Ljava/lang/Object;)V
flags: ACC_BRIDGE, ACC_SYNTHETIC
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: aload_1
2: checkcast #2 // class java/lang/Number
5: invokevirtual #3 // Method method:(Ljava/lang/Number;)V
8: return
LineNumberTable:
line 1: 0
RuntimeVisibleAnnotations:
0: #14()
}
Signature: #17 // LBase<Ljava/lang/Number;>;
SourceFile: "Derived.java"
rzeczą uwagę jest to, że istnieje adnotacja widoczna na void method(java.lang.Object)
stub w wersji Java 8, którego nie ma w wersji Java 7. To nie tylko javap
popełnianie błędu - jeśli używasz refleksji do sprawdzania adnotacji obecnych w środowisku wykonawczym, wersja Java 7 ma tylko adnotację na void method(java.lang.Number)
, a wersja Java 8 ma je na obu. Co się dzieje?
To niesamowicie irytująca zmiana zachowania. Dzięki za wskaźnik. –