java8新特性：重复注解与类型注解
1、定义一个注解类：
package com.gwolf;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
@Repeatable(MyAnnocations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnocation {
String value() default "gwolf";
}
2、定义一个注解容器类
package com.gwolf;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.*;
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnocations {
MyAnnocation[] value();
}
3、定义重复注解：
package com.gwolf;
public class TestAnotation {
@MyAnnocation("Hello")
@MyAnnocation("World")
public void show() {
}
}
4、类型注解关键字：TYPE_PARAMETER
@Repeatable(MyAnnocations.class)
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE,TYPE_PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnocation {
String value() default "gwolf";
}
5、使用类型注解：
public void test(@MyAnnocation("abc") String str) {
Class<TestAnotation> clazz = TestAnotation.class;
}
6、整体程序代码如下：
package com.gwolf;
import java.lang.reflect.Method;
public class TestAnotation {
@MyAnnocation("Hello")
@MyAnnocation("World")
public void show() {
}
public void test(@MyAnnocation("abc") String str) {
Class<TestAnotation> clazz = TestAnotation.class;
}
}
