blocks|key|1196928|text|是的，您可以像这样传递注释(就像它们是普通接口一样)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1196929|唯一不能做的事情就是在运行时创建该接口的实例。你只能接受现有的注解并传递它们。|1196930|import+java.lang.annotation.*;

public+class+Example+{

++++@Retention(RetentionPolicy.RUNTIME)
++++@Target(ElementType.METHOD)
++++public+static+@interface+Number+{
++++++++int+value();
++++}

++++@Number(value+=+42)
++++public+int+adder(final+int+b)+throws+SecurityException,+NoSuchMethodException+{
++++++++Number+number+=+getClass().getMethod("adder",+int.class).getAnnotation(Number.class);
++++++++return+addImpl(number,+b);
++++}

++++public+int+addImpl(final+Number+a,+final+int+b)+{
++++++++return+a.value()+%2B+b;
++++}

++++public+static+void+main(final+String[]+args)+throws+SecurityException,+NoSuchMethodException+{
++++++++System.out.println(new+Example().adder(0));
++++}
}|code-block|syntax|javascript|1196931|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Yes, you can pass around annotations like this (just as if they were normal interfaces).

The only thing you can't do is to create instances of that interface at runtime. You can only take existing annotations and pass them around.

<pre><code>import java.lang.annotation.*;

public class Example {

 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public static @interface Number {
 int value();
 }

 @Number(value = 42)
 public int adder(final int b) throws SecurityException, NoSuchMethodException {
 Number number = getClass().getMethod("adder", int.class).getAnnotation(Number.class);
 return addImpl(number, b);
 }

 public int addImpl(final Number a, final int b) {
 return a.value() + b;
 }

 public static void main(final String[] args) throws SecurityException, NoSuchMethodException {
 System.out.println(new Example().adder(0));
 }
}
</code></pre>

blocks|key|1196973|text|据我所知，没有您想要在add实现中使用的“注释文字”这种东西。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1196974|我认为最接近这一点的方法是声明一个接受java.lang.annotation.Annotation类型参数的方法--但是你仍然需要通过反射从类/方法对象中获取这些实例。|1196975|entityMap|0|LINK|mutability|MUTABLE|url|http://download.oracle.com/docs/cd/E17409_01/javase/6/docs/api/java/lang/annotation/Annotation.html^0|B|3|0|J|V|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@$9|T|A|U|1|V]]|E|$]]|$1|H|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|I|$J|$5|K|L|M|E|$N|O]]]]

To the best of my knowledge, there's no such thing as an "annotation literal" as you want to use it in your <code>add</code> implementation.

I think the closest thing to this would be to declare the method to take a parameter of type <a href="http://download.oracle.com/docs/cd/E17409_01/javase/6/docs/api/java/lang/annotation/Annotation.html" rel="nofollow noreferrer">java.lang.annotation.Annotation</a> - but then you'd still need to obtain those instances via reflection from the class/method objects.

blocks|key|982550|text|你可以像这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|982551|public+void+add(int+x2)+{
++++addImpl(new+Number()+{

++++++++@Override
++++++++public+int+value()+{
++++++++++++return+10;
++++++++}

++++++++@Override
++++++++public+Class<?+extends+Annotation>+annotationType()+{
++++++++++++return+Number.class;
++++++++}
++++},+x2);
}|code-block|syntax|javascript|982552|由于Number基本上是一个接口，因此您必须创建实现该接口的匿名类的实例，并将其传递给该方法。|982553|尽管我不知道你为什么要这么做。如果你需要传递一个值给某个东西，你真的应该使用一个类。|982554|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You can do it like:

<pre><code>public void add(int x2) {
 addImpl(new Number() {

 @Override
 public int value() {
 return 10;
 }

 @Override
 public Class&lt;? extends Annotation&gt; annotationType() {
 return Number.class;
 }
 }, x2);
}
</code></pre>

Since Number is basically an interface, you have to create an instance of an anonymous class that implements that interface, and pass that to the method.

Although why you want to do this is beyond me. If you need to pass a value to something, you should really use a class.

blocks|key|982778|text|Number也是一个很好的老接口，你可以实现一个具体的类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|982779|伙计们，这很有用。虽然模块主要处理在编译时固定的注释，但有时我们需要向它提供在运行时从其他来源(如xml、gush!)获得的其他信息。我们可以过度设计这个东西，或者我们可以简单地创建一个注解类型的运行时对象。|982780|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Number is also a good old interface, you can implement a concrete class.

Guys, this is useful. While a module mostly deals with annotations which are fixed at compile time, sometimes we need to feed it other info obtained at runtime from other sources(like xml, gush!) We can over-architect the thing, or we can simply creat a runtime object of the annotaion type.

blocks|key|982831|text|如果你需要在测试中传递注解，你可以模拟它。例如，JSR+303验证器的测试可能如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|982832|public+void+test()+{
++++final+TextLengthValidator+validator+=+new+TextLengthValidator();
++++validator.initialize(mock(TextLength.class));
++++final+boolean+valid+=+validator.isValid("some+text",+mock(ConstraintValidatorContext.class));
++++assertThat(valid,+is(true));
}|code-block|syntax|javascript|982833|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you need to pass annotation in test, you can make mock of it.
For example test of JSR 303 validator could look like this:

<pre><code>public void test() {
 final TextLengthValidator validator = new TextLengthValidator();
 validator.initialize(mock(TextLength.class));
 final boolean valid = validator.isValid("some text", mock(ConstraintValidatorContext.class));
 assertThat(valid, is(true));
}
</code></pre>

Guys is there a way to pass a Annotation as a direct parameter (rather by doing all the reflection overhead)? For example in the following code, I have a annotation Number that holds a int value, I want to pass as a parameter to the addImpl method, how can I do that (other than by reflection)?

Code Snippet:

<pre><code>@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
public @interface Number {
 int value();
}

public void add(int x2) {
 addImpl(@Number(value = 10) lol, x2);
}

public void addImpl(Number a, int b) {
 System.out.println(a.value() + b);
}

public static void main(String[] args) {
 new TestClass().add(3);
}
</code></pre>

Is there a way to pass a Java annotation as a parameter?

伙计们，有没有办法将Annotation作为直接参数传递(而不是做所有的反射开销)？例如，在下面的代码中，我有一个包含int值的注释号，我想作为参数传递给addImpl方法，我该如何做到这一点(除了通过反射)？代码片段：@Retention(RetentionPolicy.RUNTIME)@Target({Elemen...

问有没有办法将Java注解作为参数传递？
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