反射操作注解

• getAnnotations
• getAnnotation

package com.wang.reflection;

import java.lang.annotation.*;
import java.lang.reflect.Field;

//练习反射操作注解
public class Test12 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
        Class c1 = Class.forName("com.wang.reflection.Student2");

        //通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }

        //获得注解的value值
        TableWsh tableWsh = (TableWsh) c1.getAnnotation(TableWsh.class);
        String value = tableWsh.value();
        System.out.println(value);

        //获得类指定的注解
        Field f = c1.getDeclaredField("name");
        FieldWsh annotation = f.getAnnotation(FieldWsh.class);
        System.out.println(annotation.columnName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
    }
}

@TableWsh("db_student")
class Student2 {
    @FieldWsh(columnName = "db_id", type = "int", length = 10)
    private int id;
    @FieldWsh(columnName = "db_age", type = "int", length = 10)
    private int age;
    @FieldWsh(columnName = "db_name", type = "varchar", length = 3)
    private String name;
}

//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableWsh {
    String value();
}

//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldWsh {
    String columnName();

    String type();

    int length();
}