使用beanFactory工厂实例化容器的方式实现单例模式

//配置文件bean.properties（注意书写顺序）

accountService=com.itheima.service.impl.AccountServiceImpl
accountDao=com.itheima.dao.impl.AccountDaoImpl

 

package com.hope.factory;

import java.io.InputStream;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

/**
 * @author newcityman
 * @date 2019/11/18 - 14:44
 * 第一个：需要一个配置文件来配置我们的service和dao
 * 第二个：通过读取配置文件中配置的内容，反射创建对象
 */
public class BeanFactory {
    //定义一个properties对象
    public static Properties props;
    private static Map<String,Object> beans;
    //使用静态代码块为properties对象赋值
    static {
        try {
            //定义一个properties对象
            props = new Properties();
            //获取properties文件的流对象
            InputStream in = BeanFactory.class.getClassLoader().getResourceAsStream("bean.properties");
            props.load(in);
            //实例化容器
            beans=new HashMap<String, Object>();
            //取出配置文件中所有的Key
            Enumeration keys = props.keys();
            //遍历枚举
            while(keys.hasMoreElements()){
                //取出每个key
                String key = keys.nextElement().toString();
                //根据key获取value
                String beanPath = props.getProperty(key);
                //反射创建对象
                Object value = Class.forName(beanPath).newInstance();
                //把key和value存入容器中
                beans.put(key,value);
            }
        } catch (Exception e) {
            throw new ExceptionInInitializerError("初始化propteies失败");
        }
    }

    /**
     * 根据bean的名称获取bean对象
     *
     * @param beanName
     * @return
     */
    public static Object getBean(String beanName) {

        return beans.get(beanName);
    }
}

package com.hope.ui;

import com.hope.factory.BeanFactory;
import com.hope.service.IAccountService;

/**
 * @author newcityman
 * @date 2019/11/18 - 14:23
 */
public class Client {

    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            IAccountService as = (IAccountService)BeanFactory.getBean("accountService");
            System.out.println(as);
            as.findAll();
        }
    }