获取注解信息

反射注解操作

getAnnotations
getAnnotation

ORM

练习ORM

package com.guo.reflection;import java.lang.annotation.*;
import java.lang.reflect.Field;//联系反射操作注解
public class Test12 {public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {Class c1 = Class.forName("com.guo.reflection.Student2");//通过反射获取注解Annotation[] annotations = c1.getAnnotations();for (Annotation annotation : annotations) {System.out.println(annotation);}System.out.println("============================");//获得注解的value的值Tableguo tableguo = (Tableguo) c1.getAnnotation(Tableguo.class);String value = tableguo.value();System.out.println(value);System.out.println("============================");//获得类指定的注解Field f = c1.getDeclaredField("id");Filedguo annotation = f.getAnnotation(Filedguo.class);System.out.println(annotation.columnName());System.out.println(annotation.type());System.out.println(annotation.length());System.out.println("============================");f = c1.getDeclaredField("age");annotation = f.getAnnotation(Filedguo.class);System.out.println(annotation.columnName());System.out.println(annotation.type());System.out.println(annotation.length());System.out.println("============================");f = c1.getDeclaredField("name");annotation = f.getAnnotation(Filedguo.class);System.out.println(annotation.columnName());System.out.println(annotation.type());System.out.println(annotation.length());System.out.println("============================");}
}@Tableguo("db-student")
class Student2{@Filedguo(columnName = "db_id",type = "int",length = 10)private int id;@Filedguo(columnName = "db_age",type = "int",length = 10)private int age;@Filedguo(columnName = "db_name",type = "varchar",length = 3)private String name;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;}@Overridepublic String toString() {return "Student2{" +"id=" + id +", age=" + age +", name='" + name + '\'' +'}';}
}//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Tableguo{String value();
}//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Filedguo{String columnName();String type();int length();
}