註解

refer from :http://www.iteye.com/topic/223891

註解的學習

1.聲明瞭一個註釋 

@Retention(RetentionPolicy.RUNTIME)
public @interface TestAnno {

}

2.聲明瞭一個含有private變量a的類 

public class TestAnnotation {
    @TestAnno
    private String a;

    public String getA() {
        return a;
    }

    public void setA(String a) {
        this.a = a;
    }

}

3.通過反射爲a賦值 

public class MainTest {
    public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException {
        TestAnnotation ta=new TestAnnotation();
        Field[] fs=TestAnnotation.class.getDeclaredFields();
        for(int i=0;i<fs.length;i++){
            if(fs[i].isAnnotationPresent(TestAnno.class)){
                fs[i].setAccessible(true);
                fs[i].set(ta, "你好");
            }
        }
        System.out.println(ta.getA());
    }
}

關鍵是fs[i].setAccessible(true);這個方法，如果不設置這個方法則會拋出java.lang.IllegalAccessException的異常。網上也有人說setAccessible有安全性限制不要隨便亂用。不過至少可以做到