反射机制之反射操作泛型和操作注解

package com.reflection;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.*;
import java.util.Map;
//通过反射获取泛型
public class Test11 {
    public void test01(Map<String,User> map, List<User> list){
        System.out.println("test01");
    }
    public Map<String, User> test02(){
        System.out.println("test02");
        return null;
    }
    public static void main(String[] args) throws NoSuchMethodException {
        //类名.class 快速创建爱你对象
        Method method = Test11.class.getMethod("test01", Map.class, List.class);
        Type[] genericParameterTypes = method.getGenericParameterTypes();//获得泛型参数信息
        for (Type genericParameterType : genericParameterTypes) {
            System.out.println("#"+ genericParameterType);
            if(genericParameterType instanceof ParameterizedType){ //泛型参数类型是否等于结构化参数类型
                Type[] actualTypeArguments = ((ParameterizedType) genericParameterType).getActualTypeArguments();//强转之后的真实参数类型
                for (Type actualTypeArgument : actualTypeArguments) {
                    System.out.println(actualTypeArgument);
                }
            }
        }
        method = Test11.class.getMethod("test02",null);
        Type genericReturnType = method.getGenericReturnType();
        if(genericReturnType instanceof ParameterizedType){ //泛型参数类型是否等于结构化参数类型
            Type[] actualTypeArguments = ((ParameterizedType) genericReturnType).getActualTypeArguments();//强转之后的真实参数类型
            for (Type actualTypeArgument : actualTypeArguments) {
                System.out.println(actualTypeArgument);
            }
        }
    }
}

package com.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.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的值
        Tablehxl tablehxl = (Tablehxl) c1.getAnnotation(Tablehxl.class);
        String value = tablehxl.value();
        System.out.println(value);
        //获得类指定的注解
        Field f = c1.getDeclaredField("name");
        Fieldhxl annotation = f.getAnnotation(Fieldhxl.class);
        System.out.println(annotation.columName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
    }
}
@Tablehxl("db_student")
class Student2{
    @Fieldhxl(columName = "db_id", type = "int", length = 10)
    private int id;
    @Fieldhxl(columName = "db_age", type = "int", length = 10)
    private int age;
    @Fieldhxl(columName = "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 Student2() {
    }
    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 + '\'' +
                '}';
    }
}
//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Tablehxl{
    String value();
}
//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface Fieldhxl{
    String columName();
    String type();
    int length();
}
/*
@com.reflection.Tablehxl(value=db_student)
db_student
db_name
varchar
3
*/