简单模拟IOC容器：返回对象并能抛出异常

package com.zzj.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

//范围只限定类，存在周期运行后
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Component {

}

package com.zzj.vo;
public class Elephant {

}

package com.zzj.vo;
import com.zzj.annotation.Component;
@Component
public class Lion {

}

package com.zzj.vo;
import com.zzj.annotation.Component;
@Component
public class Tiger {

}

package com.zzj;

import java.io.File;
import java.util.HashMap;
import java.util.Map;

import org.springframework.beans.factory.NoSuchBeanDefinitionException;

import com.zzj.annotation.Component;

public class Application {

        //定义map集合存放对应类和对应的class对象
    private static Map<Class,Object> map = new HashMap<Class,Object>();
    
    static{
        
        String packageName = "com.zzj.vo";
        //获取包的绝对路径
        String path = ClassLoader.getSystemResource("").getPath() + packageName.replace(".",File.separator);
        //路径中文转码,由于是静态方法不能使用
        //path = java.net.URLDecoder.decode(path,"utf-8");
        //采用字符替换
        path = path.replace("%e7%a8%8b%e5%ba%8f%e7%8c%bf","程序猿");
        
        //获取包里的所有类
        File[] files = new File(path).listFiles();
        
        //获取所有类的相对路径（包名+类名，无扩展名）
        for (File file : files){
            String fileName = file.getName();
            String className = packageName + "." + fileName.substring(0,fileName.indexOf("."));
            
            //将获取的类放入Map集合，key为类型，value为映射对象(默认为对象地址)
            try {
                Class clazz = Class.forName(className);
                if(clazz.getAnnotation(Component.class) != null){
                    map.put(clazz,clazz.newInstance());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            
        }
        
    }
    
        //抛出异常
        public static Object getBean(Class clazz){
        Object object =  map.get(clazz);
        if(object == null){
            throw new NoSuchBeanDefinitionException("No qualifying bean of type ‘"+clazz.getName()+"‘available");
        }
        
        return object;
    }
    
}
    

package com.zzj.exception;

public class NoSuchBeanDefinitionException extends RuntimeException{

    private static final long serialVersionUID = 8124869159299733396L;

    public NoSuchBeanDefinitionException(String msg) {
        
        super(msg);
        
    }
    
}

package com.zzj.test;

import com.zzj.vo.Lion;

import com.zzj.Application;

/*
 已知com.zzj.vo包下分别有Tiger、lion、Elephant三个Java源文件，请据此实现以下功能：
①、自定义一个名为Component的注解，要求该注解只能用于类且代码运行时该注解依然有效；
②、为Tiger和Lion类添加component注解
③、在Application类中定义静态代码块，该代码块可自动将有Component注解修饰的类创建对象并放在Map集合中；然后定义一个名为getBean的static方法，
要求传入Class类实例时返回该Class类对应类的对象，如果没有Class类对应的对象，则引发NoSuchBeanDefinitionException异常并
提示“No qualifying bean of type ‘com.lq.vo.类名‘available”；
*/
public class Test {
    
    public static void main(String[] args){
        
        Object object = Application.getBean(Lion.class);
        System.out.println(object);
        
    }
    
}