运行时获取注解信息 [英] get the annotation information at runtime

问题描述

不知道有没有什么办法可以在运行时获取一个类的注解信息?由于我想获得单独注释的属性.

I wonder if there is any way I can get the annotation information of a class at runtime? Since I want to get the properties that sepcifily annotated.

示例:

class TestMain {
    @Field(
            store = Store.NO)
    private String  name;
    private String  password;
    @Field(
            store = Store.YES)
    private int     age;

    //..........getter and setter
}

注释来自休眠搜索，现在我想要的是获取TestMain"的哪个属性被注释作为字段"(在示例中，它们是[name,age])，并且在运行时是stored(store=store.yes)"(在示例中，它们是 [age]).

The annotations come from the hibernate-search,and now what I want is get which property of the "TestMain" is annotated as a 'field'(in the example,they are [name,age]),and which is 'stored(store=store.yes)'(in the example,they are [age]) at runtime.

有什么想法吗?

更新:

public class FieldUtil {
public static List<String> getAllFieldsByClass(Class<?> clazz) {
    Field[] fields = clazz.getDeclaredFields();
    ArrayList<String> fieldList = new ArrayList<String>();
    ArrayList<String> storedList=new ArrayList<String>();
    String tmp;
    for (int i = 0; i < fields.length; i++) {
        Field fi = fields[i];
        tmp = fi.getName();
        if (tmp.equalsIgnoreCase("serialVersionUID"))
            continue;
        if (fi.isAnnotationPresent(org.hibernate.search.annotations.Field.class)) {
            //it is a "field",add it to list.
            fieldList.add(tmp);

            //make sure if it is stored also
            Annotation[] ans = fi.getAnnotations();
            for (Annotation an : ans) {
                //here,how to get the detail annotation information
                //I print the value of an,it is something like this:
                //@org.hibernate.search.annotations.Field(termVector=NO, index=UN_TOKENIZED, store=NO, name=, boost=@org.hibernate.search.annotations.Boost(value=1.0), analyzer=@org.hibernate.search.annotations.Analyzer(impl=void, definition=), bridge=@org.hibernate.search.annotations.FieldBridge(impl=void, params=[]))

                //how to get the parameter value of this an? using the string method?split?
            }
        }

    }
    return fieldList;
}

}

推荐答案

是的，当然.您的代码示例实际上并未获取类的注释信息，而是获取字段的注释信息，但代码类似.您只需要获取您感兴趣的类、方法或字段，然后在其上调用getAnnotation(AnnotationClass.class)".

Yes, of course. Your code sample does not actually get annotation information for class, but for fields, but code is similar. You just need to get Class, Method or Field you are interested in, then call "getAnnotation(AnnotationClass.class)" on it.

唯一需要注意的是，注解定义必须使用正确的 RetentionPolicy，以便将注解信息存储在字节码中.类似的东西:

The only other thing to notice is that annotation definition must use proper RetentionPolicy so that annotation information is stored in byte code. Something like:

@Target({ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation { ... }

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