Java-反射-获取注解信息

小鱼儿 2024-04-20 08:12 5阅读 0赞

代码：

package com.cdmt.java.annotation.historyhandler;
    
    import java.lang.annotation.*;
    import java.lang.reflect.Field;
    
    /**
     * 反射操作注解
     **/
    public class Test11 {
        public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
            //通过反射获取注解
            Class c1 = Class.forName("com.cdmt.java.annotation.historyhandler.Student2");
            //获取全部注解
            Annotation[] annotations = c1.getAnnotations();
            for(Annotation annotation :annotations){
                System.out.println(annotation);
            }
    
            //获取注解value的值
            TableStudent tableStudent = (TableStudent)c1.getAnnotation(TableStudent.class);
            System.out.println(tableStudent.value());
            
            //获取指定类注解
            Field name = c1.getDeclaredField("name");
            FieldStudent annotation = name.getAnnotation(FieldStudent.class);
            System.out.println(annotation.columName());
            System.out.println(annotation.type());
            System.out.println(annotation.length());
        }
    }
    
    @TableStudent("db_student")
    class Student2{
        @FieldStudent(columName = "id",type = "int",length = 10)
        private int id;
        @FieldStudent(columName = "age",type = "int",length = 10)
        private int age;
        @FieldStudent(columName = "name",type = "varchar",length = 10)
        private String  name;
    
        public Student2() {
        }
    
        public Student2(int id, int age, String name) {
            this.id = id;
            this.age = age;
            this.name = name;
        }
    
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public String toString() {
            return "Student2{" +
                    "id=" + id +
                    ", age=" + age +
                    ", name='" + name + '\'' +
                    '}';
        }
    }
    
    //类名注解
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @interface TableStudent{
        String value();
    }
    
    //字段名
    @Target(ElementType.FIELD)
    @Retention(RetentionPolicy.RUNTIME)
    @interface FieldStudent{
        String columName();
        String type();
        int length();
    }

结果：

![20190920105914903.png][]

[20190920105914903.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/18/65754267a36741d79834e520613bccce.png