java——注解处理器

Java提供了两种方式来处理注解：第一种是利用运行时反射机制；另一种是使用Java提供的API来处理编译期的注解。

运行时通过反射：仅当定义的注解的@Retention为RUNTIME时，才能够通过运行时的反射机制来处理注解。

https://www.jb51.net/article/132038.htm

FruitName.java

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitName {
    String value() default "";
}

FruitColor.java

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitColor {
    /**
     * 颜色枚举
     * @author peida
     *
     */
    public enum Color{
        BULE,RED,GREEN
    }
    ;
    /**
     * 颜色属性
     * @return
     */
    Color fruitColor() default Color.GREEN;
}

FruitProvider.java

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitProvider {
    /**
     * 供应商编号
     * @return
     */
    public int id() default -1;
    /**
     * 供应商名称
     * @return
     */
    public String name() default "";
    /**
     * 供应商地址
     * @return
     */
    public String address() default "";
}

Apple.java

public 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");
    }
}

FruitInfoUtil.java

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(FruitName.class)){
                FruitName fruitName = (FruitName) field.getAnnotation(FruitName.class);
                strFruitName=strFruitName+fruitName.value();
                System.out.println(strFruitName);
            } else if(field.isAnnotationPresent(FruitColor.class)){
                FruitColor fruitColor= (FruitColor) field.getAnnotation(FruitColor.class);
                strFruitColor=strFruitColor+fruitColor.fruitColor().toString();
                System.out.println(strFruitColor);
            } 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);
            }
        }
    }
}

FruitRun.java

public class FruitRun {
    /**
     * @param args
     */
    public static void main(String[] args) {
        FruitInfoUtil.getFruitInfo(Apple.class);
    }
}

编译时：

https://blog.csdn.net/qfanmingyiq/article/details/75432854