工厂模式解耦【三】分析工厂模式中的问题并改造

作为一个初学者，想要在这方面获得巨大的提升，必然要耐得住寂寞，和源码死磕

我们修改一下代码并输出观察

package cn.itycu.ui;

import cn.itycu.factory.BeanFactory;
import cn.itycu.service.IAccountService;
import cn.itycu.service.impl.AccountServiceImpl;

/**
 * @author 披风少年
 * @version 1.0
 * @date 2020/5/23 15:21
 * 模拟一个表现层，用于调用业务层
 */
public class Client {
    public static void main(String[] args) {
//        IAccountService accountService = new AccountServiceImpl();
        for (int i = 0; i < 5; i++) {
            IAccountService accountService = (IAccountService) BeanFactory.getBean("accountService");
            System.out.println(accountService);
        }
//        accountService.saveAccount();
    }
}
-----------------------------输出结果-------------------------------
"C:\Program Files (x86)\Java\jdk1.8.0_144\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=26505:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\charsets.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\deploy.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\access-bridge-32.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\cldrdata.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\dnsns.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\jaccess.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\jfxrt.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\localedata.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\nashorn.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunec.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunjce_provider.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunmscapi.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunpkcs11.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\zipfs.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\javaws.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jce.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jfr.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jfxswt.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jsse.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\management-agent.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\plugin.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\resources.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\rt.jar;C:\Users\15402\Desktop\demo01\target\classes" cn.itycu.ui.Client
cn.itycu.service.impl.AccountServiceImpl@a14482
cn.itycu.service.impl.AccountServiceImpl@140e19d
cn.itycu.service.impl.AccountServiceImpl@17327b6
cn.itycu.service.impl.AccountServiceImpl@14ae5a5
cn.itycu.service.impl.AccountServiceImpl@131245a

Process finished with exit code 0

我们发现对象 accountService 是多例的，每一次请求都会创建一个新的对象，执行效率肯定没有单例对象高。
我们采用map在初始化时创建对象，这样就不用反复创建对象了，修改代码如下

package cn.itycu.factory;

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

/**
 * @author 披风少年
 * @version 1.0
 * @date 2020/5/23 15:47
 * 一个创建bean对象的工厂
 * Bean：在计算机英语中有可重用组件的含义
 * 通过工厂创建service和dao对象
 */
public class BeanFactory {
    //定义一个properties对象并用static代码块儿对对象进行赋值
    private static Properties props;
    //定义一个map用于存放我们要创建的对象，我们称它为容器
    private static Map<String, Object> beans;
    static {
        try {
            //实例化对象,耦合只能减小不能消除，所以必要的new我们还是需要的
            props = new Properties();
            /**
             * 获取properties文件的流对象
             * 使用类加载器来获取bean.properties文本对象
             * 创建在resources目录下的文件最终会成为类根目录下的文件
             */
            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<Object> 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();
                //存入容器
                beans.put(key, value);
            }
        } catch (Exception e) {
            throw new ExceptionInInitializerError("初始化 properties 失败！");
        }
    }

    /**
     * 根据bean的名称获取单例对象
     * @param beanName
     * @return
     */
    public static Object getBean(String beanName) {
        return beans.get(beanName);
    }

    /**
     * 根据Bean的名词获取bean对象
     * 采用泛型编程，增加工厂的复用性
     * @param beanName
     * @return
     */
//    public static Object getBean(String beanName) {
//        Object bean = null;
//        try {
//            String beanPath = props.getProperty(beanName);
//            // newInstance 每次都会调用默认构造方法创建对象
//            bean = Class.forName(beanPath).newInstance();
//        } catch (Exception e) {
//            e.printStackTrace();
//        }
//        return bean;
//    }
}
-----------------------------输出结果-------------------------------
"C:\Program Files (x86)\Java\jdk1.8.0_144\bin\java.exe" "-javaagent:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.3\lib\idea_rt.jar=27023:D:\Program Files\JetBrains\IntelliJ IDEA 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\charsets.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\deploy.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\access-bridge-32.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\cldrdata.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\dnsns.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\jaccess.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\jfxrt.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\localedata.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\nashorn.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunec.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunjce_provider.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunmscapi.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\sunpkcs11.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\ext\zipfs.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\javaws.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jce.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jfr.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jfxswt.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\jsse.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\management-agent.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\plugin.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\resources.jar;C:\Program Files (x86)\Java\jdk1.8.0_144\jre\lib\rt.jar;C:\Users\15402\Desktop\demo01\target\classes" cn.itycu.ui.Client
cn.itycu.service.impl.AccountServiceImpl@a14482
cn.itycu.service.impl.AccountServiceImpl@a14482
cn.itycu.service.impl.AccountServiceImpl@a14482
cn.itycu.service.impl.AccountServiceImpl@a14482
cn.itycu.service.impl.AccountServiceImpl@a14482

Process finished with exit code 0

我们发现输出五次都是同一个对象