Java注解的定义与使用

一：自定义注解

/**
 * 水果颜色注解
 * @author dell
 *
 */

@Target(ElementType.FIELD)//应用于字段
@Retention(RetentionPolicy.RUNTIME)
public @interface FruitColor {
	public enum Color {bule,red,green};
	
	Color fruitColor() default Color.green;
}

/**
 * 水果名称注解
 * @author dell
 *
 */
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface FruitName {
	String value() default "";
}

二：被注解的类

public class Apple {
	@FruitName("apple")
	private String appleName;
	
	@FruitColor(fruitColor=Color.red)
	private String appleColor;
	
	@FruitProvider(id=1,name="红富士集团",address="广东省广州市天河区")
	private String appleProvider;
	//set get省略...
}

三：注解处理器

/**
 * 注解处理器
 * 
 * @author dell
 *
 */
public class FruitInfoUtil {
	public static void 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();

		for (Field field : fields) {
			if (field.isAnnotationPresent(FruitColor.class)) {
				FruitColor fruitColor = field.getAnnotation(FruitColor.class);
				strFruitColor = strFruitColor + fruitColor.fruitColor().toString();
				System.out.println(strFruitColor);
			} else if (field.isAnnotationPresent(FruitProvider.class)) {
				FruitProvider fruitProvider = field.getAnnotation(FruitProvider.class);
				strFruitProvicer = strFruitProvicer + fruitProvider.address() + fruitProvider.id()
						+ fruitProvider.name();
				System.out.println(strFruitProvicer);
			} else if (field.isAnnotationPresent(FruitName.class)) {
				FruitName fruitName = field.getAnnotation(FruitName.class);
				strFruitName = strFruitName + fruitName.value();
				System.out.println(strFruitName);
			}
		}

	}

}

四：使用

public static void main(String[] args) {
		
		FruitInfoUtil.getFruitInfo(Apple.class);
		
	}

五：结果输出

水果名称:apple
水果颜色:red
供应商信息:广东省广州市天河区1红富士集团