blocks|key|1421678|text|不可能在运行时添加注释，听起来您需要引入一个adapter，模块B使用该A包装模块A中的对象，以公开所需的带注释的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1421679|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Adapter_pattern^0|M|7|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

It's not possible to add an annotation at runtime, it sounds like you need to introduce an <a href="http://en.wikipedia.org/wiki/Adapter_pattern" rel="noreferrer">adapter</a> that module B uses to wrap the object from module A exposing the required annotated methods.

blocks|key|1206676|text|这可以通过Javassist等字节码插装库来实现。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1206677|具体地说，查看AnnotationsAttribute类以获取有关如何创建/设置批注示例，并查看tutorial+section+on+bytecode+API以获取有关如何操作类文件的一般指南。|1206678|然而，这绝不是简单和直接的-我不推荐这种方法，建议您考虑Tom的答案，除非您需要为大量的类这样做(或者所说的类直到运行时才可用，因此编写适配器是不可能的)。|1206679|entityMap|0|LINK|mutability|MUTABLE|url|http://www.csg.is.titech.ac.jp/~chiba/javassist/|1|http://www.csg.is.titech.ac.jp/~chiba/javassist/html/javassist/bytecode/AnnotationsAttribute.html|2|http://www.csg.is.titech.ac.jp/~chiba/javassist/tutorial/tutorial3.html#intro^0|5|9|0|0|7|K|1|1C|W|2|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]|$A|11|B|12|1|13]]|C|$]]|$1|F|3|G|5|6|7|14|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]|R|$5|K|L|M|C|$N|S]]]]

It's possible via bytecode instrumentation library such as <a href="http://www.csg.is.titech.ac.jp/~chiba/javassist/" rel="noreferrer">Javassist</a>.

In particular, take a look at <a href="http://www.csg.is.titech.ac.jp/~chiba/javassist/html/javassist/bytecode/AnnotationsAttribute.html" rel="noreferrer">AnnotationsAttribute</a> class for an example on how to create / set annotations and <a href="http://www.csg.is.titech.ac.jp/~chiba/javassist/tutorial/tutorial3.html#intro" rel="noreferrer">tutorial section on bytecode API</a> for general guidelines on how to manipulate class files.

This is anything but simple and straightforward, though - I would NOT recommend this approach and suggest you consider Tom's answer instead unless you need to do this for a huge number of classes (or said classes aren't available to you until runtime and thus writing an adapter is impossible).

blocks|key|1421805|text|可以通过Proxy在运行时创建注释。然后，您可以像其他答案中所建议的那样，通过反射将它们添加到Java对象中(但您最好找到另一种方法来处理这一问题，因为通过反射处理现有类型可能会很危险，而且很难调试)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1421806|但这并不容易..。我编写了一个名为Javanna的库，我希望这是适当的，只是为了使用一个干净的API来轻松地完成这项工作。|1421807|它在JCenter和Maven+Central中。|1421808|使用它：|1421809|@Retention(+RetentionPolicy.RUNTIME+)
@interface+Simple+{
++++String+value();
}

Simple+simple+=+Javanna.createAnnotation(+Simple.class,+
++++new+HashMap<String,+Object>()+{{
++++++++put(+"value",+"the-simple-one"+);
++++}}+);|code-block|syntax|javascript|1421810|如果映射的任何条目与注释声明的字段和类型不匹配，就会抛出异常。如果缺少任何没有默认值的值，则会引发异常。|1421811|这使得可以假设每个成功创建的注释实例都可以像编译时注释实例一样安全地使用。|1421812|另外，这个库还可以解析注释类，并将注释的值作为Map返回：|1421813|Map<String,+Object>+values+=+Javanna.getAnnotationValues(+annotation+);|1421814|这对于创建迷你框架很方便。|1421815|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Proxy.html|1|https://github.com/renatoathaydes/javanna|2|https://bintray.com/search?query=javanna|3|http://search.maven.org/#search%257Cga%257C1%257Ccom.athaydes.javanna^0|4|5|0|0|H|7|1|0|2|7|2|A|D|3|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@$A|1D|B|1E|1|1F]]|C|$]]|$1|D|3|E|5|6|7|1G|8|@]|9|@$A|1H|B|1I|1|1J]]|C|$]]|$1|F|3|G|5|6|7|1K|8|@]|9|@$A|1L|B|1M|1|1N]|$A|1O|B|1P|1|1Q]]|C|$]]|$1|H|3|I|5|6|7|1R|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|1S|8|@]|9|@]|C|$M|N]]|$1|O|3|P|5|6|7|1T|8|@]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1U|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|1V|8|@]|9|@]|C|$]]|$1|U|3|V|5|L|7|1W|8|@]|9|@]|C|$M|N]]|$1|W|3|X|5|6|7|1X|8|@]|9|@]|C|$]]|$1|Y|3|-4|5|6|7|1Y|8|@]|9|@]|C|$]]]|Z|$10|$5|11|12|13|C|$14|15]]|16|$5|11|12|13|C|$14|17]]|18|$5|11|12|13|C|$14|19]]|1A|$5|11|12|13|C|$14|1B]]]]

It is possible to create annotations at runtime via a <a href="https://docs.oracle.com/javase/7/docs/api/java/lang/reflect/Proxy.html" rel="noreferrer">Proxy</a>. You can then add them to your Java objects via reflection as suggested in other answers (but you probably would be better off finding an alternative way to handle that, as messing with the existing types via reflection can be dangerous and hard to debug).

But it is not very easy... I wrote a library called, I hope appropriately, <a href="https://github.com/renatoathaydes/javanna" rel="noreferrer">Javanna</a> just to do this easily using a clean API.

It's in <a href="https://bintray.com/search?query=javanna" rel="noreferrer">JCenter</a> and <a href="http://search.maven.org/#search%7Cga%7C1%7Ccom.athaydes.javanna" rel="noreferrer">Maven Central</a>.

Using it:

<pre><code>@Retention( RetentionPolicy.RUNTIME )
@interface Simple {
 String value();
}

Simple simple = Javanna.createAnnotation( Simple.class, 
 new HashMap&lt;String, Object&gt;() {{
 put( "value", "the-simple-one" );
 }} );
</code></pre>

If any entry of the map does not match the annotation declared field(s) and type(s), an Exception is thrown. If any value that has no default value is missing, an Exception is thrown.

This makes it possible to assume every annotation instance that is created successfully is as safe to use as a compile-time annotation instance.

As a bonus, this lib can also parse annotation classes and return the values of the annotation as a Map:

<pre><code>Map&lt;String, Object&gt; values = Javanna.getAnnotationValues( annotation );
</code></pre>

This is convenient for creating mini-frameworks.

Is it possible to add an annotation to an object (in my case in particular, a Method) at runtime?

For a bit more explanation: I have two modules, moduleA and moduleB. moduleB depends upon moduleA, which doesn't depend upon anything. (modA is my core datatypes and interfaces and such, modB is db/data layer) modB also depends on externalLibrary. In my case, modB is handing off a class from modA to externalLibrary, which needs certain methods to be annotated. The specific annotations are all part of externalLib and, as I said, modA doesn't depend on externalLib and I'd like to keep it that way.

So, is this possible, or do you have suggestions for other ways of looking at this problem?

Adding Java Annotations at Runtime

Java

可以在运行时向对象(在我的例子中，特别是方法)添加注释吗？更多的解释:我有两个模块，moduleA和moduleB。moduleB依赖于moduleA，它不依赖于任何东西。(modA是我的核心数据类型和接口，modB就是db/数据层) modB也依赖于externalLibrary。在我的例子中，modB将一个类从mo...

问在运行时添加Java注释
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