java-注解

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import java.lang.reflect.Field;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * 水果名称注解
 */
@Target(FIELD)
@Retention(RUNTIME)
@Documented
@interface FruitName {
    String value() default "";
}


/**
 * 水果颜色注解
 */
@Target(FIELD)
@Retention(RUNTIME)
@Documented
@interface FruitColor {
    /**
     * 颜色枚举
     */
    public enum Color{ BLUE,RED,GREEN};

    /**
     * 颜色属性
     */
    Color fruitColor() default Color.GREEN;

}
/**
 * 水果供应者注解
 */
@Target(FIELD)
@Retention(RUNTIME)
@Documented
@interface FruitProvider {
    /**
     * 供应商编号
     */
    public int id() default -1;

    /**
     * 供应商名称
     */
    public String name() default "";

    /**
     * 供应商地址
     */
    public String address() default "";
}

/**
 * 注解处理器
 */
class FruitInfoUtil {
    public static Apple getFruitInfo(Class<?> clazz) {

        String strFruitName = " 水果名称：";
        String strFruitColor = " 水果颜色：";
        String strFruitProvicer = "供应商信息：";

        Field[] fields = clazz.getDeclaredFields();
        Apple a=null;

        if(clazz.getName().equals("Apple")){
            a=new Apple();
            for (Field field : fields) {
                if (field.isAnnotationPresent(FruitName.class)) {
                    FruitName fruitName = (FruitName) field.getAnnotation(FruitName.class);
                    strFruitName = strFruitName + fruitName.value();
                    System.out.println(strFruitName);
                    a.setAppleName(fruitName.value());
                } else if (field.isAnnotationPresent(FruitColor.class)) {
                    FruitColor fruitColor = (FruitColor) field.getAnnotation(FruitColor.class);
                    strFruitColor = strFruitColor + fruitColor.fruitColor().toString();
                    System.out.println(strFruitColor);
                    a.setAppleColor(fruitColor.fruitColor().toString());
                } else if (field.isAnnotationPresent(FruitProvider.class)) {
                    FruitProvider fruitProvider = (FruitProvider) field.getAnnotation(FruitProvider.class);
                    strFruitProvicer = " 供应商编号：" + fruitProvider.id() + " 供应商名称：" + fruitProvider.name() + " 供应商地址：" + fruitProvider.address();
                    System.out.println(strFruitProvicer);
                    a.setAppleProvider(strFruitProvicer);
                }
            }
        }
        return a;

    }
}

/**
 * 注解使用
 */
class Apple {

    @FruitName("Apple")
    private String appleName;

    @FruitColor(fruitColor= FruitColor.Color.RED)
    private String appleColor;

    @FruitProvider(id=1,name="陕西红富士集团",address="陕西省西安市延安路89号红富士大厦")
    private String appleProvider;

    public void setAppleColor(String appleColor) {
        this.appleColor = appleColor;
    }
    public String getAppleColor() {
        return appleColor;
    }

    public void setAppleName(String appleName) {
        this.appleName = appleName;
    }
    public String getAppleName() {
        return appleName;
    }

    public void setAppleProvider(String appleProvider) {
        this.appleProvider = appleProvider;
    }
    public String getAppleProvider() {
        return appleProvider;
    }

    public void displayName(){
        System.out.println("水果的名字是：苹果");
    }

    @Override
    public String toString() {
        return "Apple{" +
                "appleName='" + appleName + '\'' +
                ", appleColor='" + appleColor + '\'' +
                ", appleProvider='" + appleProvider + '\'' +
                '}';
    }
}
public class AnnotationTest {
    public static void main(String[] args) {
        System.out.println(FruitInfoUtil.getFruitInfo(Apple.class));
    }
}