java工厂模式读取配置文件*.properties信息

逃离我推掉我的手 2021-12-21 07:59 373阅读 0赞

一、创建两个接口并实现

package com.zz.my_spring_five.practice.second_chapter.individualcomponents.message;
    
    /**
     * @author ：zhang
     * @description：
     * @date ：Created in 2019/6/27 10:56
     */
    public interface MessageProvider {
    
        String getMessage();
    
    }

package com.zz.my_spring_five.practice.second_chapter.individualcomponents.message;
    
    /**
     * @author ：zhang
     * @description：
     * @date ：Created in 2019/6/27 10:59
     */
    public class HelloWorldMessageProvider implements MessageProvider{
        @Override
        public String getMessage() {
            return "Hello World";
        }
    }

package com.zz.my_spring_five.practice.second_chapter.individualcomponents.message;
    
    public interface MessageRenderer {
    
        void Render();
    
        void setMessageProvider(MessageProvider messageProvider);
    
        MessageProvider getMessageProvider();
    
    }

package com.zz.my_spring_five.practice.second_chapter.individualcomponents.message;
    
    /**
     * @author ：zhang
     * @description：
     * @date ：Created in 2019/6/27 11:00
     */
    public class StandardOutMessageRenderer implements MessageRenderer{
    
        private MessageProvider messageProvider;
    
        @Override
        public void Render() {
            if (messageProvider == null) {
                System.out.println(" You must set the property messageProvider class： StandardOutMessageRenderer . class. getName ()");
            } else {
                System.out.println("Hello World");
            }
        }
    
        @Override
        public void setMessageProvider(MessageProvider messageProvider) {
            this.messageProvider = messageProvider;
        }
    
        @Override
        public MessageProvider getMessageProvider() {
            return this.messageProvider;
        }
    }

二、工厂类并读取配置文件

配置文件msf.properties（位于springBoot的resources文件夹下）

renderer.class=com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.StandardOutMessageRenderer
    provider.class=com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.HelloWorldMessageProvider

import com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.MessageProvider;
    import com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.MessageRenderer;
    
    import java.io.IOException;
    import java.util.Properties;
    
    /**
     * @author ：zhang
     * @description：
     * @date ：Created in 2019/6/27 11:16
     */
    public class MessageSupportFactory {
    
        private static MessageSupportFactory factory;
    
        private Properties properties;
    
        private MessageProvider messageProvider;
    
        private MessageRenderer messageRenderer;
    
        private MessageSupportFactory() {
            properties = new Properties();
            try {
                properties.load(this.getClass().getResourceAsStream("/msf.properties"));
                String rendererClass = properties.getProperty("renderer.class");
                String providerClass = properties.getProperty("provider.class");
                messageRenderer = (MessageRenderer) Class.forName(rendererClass).newInstance();
                messageProvider = (MessageProvider) Class.forName(providerClass).newInstance();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
    
        static {
            factory = new MessageSupportFactory();
        }
    
        public static MessageSupportFactory getFactory(){
            return factory;
        }
    
        public MessageProvider getMessageProvider() {
            return messageProvider;
        }
    
        public MessageRenderer getMessageRenderer() {
            return messageRenderer;
        }
    
    }

三、main方法

package com.zz.my_spring_five.practice.second_chapter.individualcomponents.supportfactory;
    
    import com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.MessageProvider;
    import com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.MessageRenderer;
    
    /**
     * @author ：zhang
     * @description：
     * @date ：Created in 2019/6/27 11:36
     */
    public class MainClass {
    
        public static void main(String... args) {
            MessageProvider messageProvider = MessageSupportFactory.getFactory().getMessageProvider();
            MessageRenderer messageRenderer = MessageSupportFactory.getFactory().getMessageRenderer();
            messageRenderer.setMessageProvider(messageProvider);
            messageRenderer.Render();
        }
    
    }

四、运行main方法输出Hello World

说明：

出现错误

Exception in thread "main" java.lang.ExceptionInInitializerError
    	at com.zz.my_spring_five.practice.second_chapter.individualcomponents.supportfactory.MainClass.main(MainClass.java:14)
    Caused by: java.lang.NullPointerException
    	at java.util.Properties$LineReader.readLine(Properties.java:434)
    	at java.util.Properties.load0(Properties.java:353)
    	at java.util.Properties.load(Properties.java:341)
    	at com.zz.my_spring_five.practice.second_chapter.individualcomponents.supportfactory.MessageSupportFactory.<init>(MessageSupportFactory.java:27)
    	at com.zz.my_spring_five.practice.second_chapter.individualcomponents.supportfactory.MessageSupportFactory.<clinit>(MessageSupportFactory.java:44)
    	... 1 more
    
    Process finished with exit code 1

则是properties文件在加载读取的时候错误，修改以下代码中的"/msf.properties",此处已经配置好

properties.load(this.getClass().getResourceAsStream("/msf.properties"));

扩展：spring经典配置获取实例，配置xml注入，添加app-context.xml，放到resource文件夹下

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:p="http://www.springframework.org/schema/p"
           xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    
        <bean id="provider"
              class="com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.HelloWorldMessageProvider" />
    
        <bean id="renderer"
              class="com.zz.my_spring_five.practice.second_chapter.individualcomponents.message.StandardOutMessageRenderer"
              p:messageProvider-ref="provider" />
    </beans>

main方法测试

public class HelloWorldSpringDI {
    
        public static void main(String... args) {
            ApplicationContext context = new ClassPathXmlApplicationContext("app-context.xml");
            MessageRenderer messageRenderer = context.getBean("renderer", MessageRenderer.class);
            messageRenderer.Render();
        }
    }

使用注解的方式配置获取实例，添加配置文件HelloWorldConfiguration.java

@Configuration
    public class HelloWorldConfiguration {
    
        // 相当于<bean id="provider" class="..." />
        @Bean
        public MessageProvider provider() {
            return new HelloWorldMessageProvider();
        }
    
        // 相当于<bean id="renderer" class="..." />
        @Bean
        public MessageRenderer renderer(){
            MessageRenderer renderer = new StandardOutMessageRenderer();
            renderer.setMessageProvider(provider());
            return renderer;
        }
    }

main方法测试

public class HelloWorldSpringAnnotated {
    
        public static void main(String... args) {
            ApplicationContext context = new AnnotationConfigApplicationContext(HelloWorldConfiguration.class);
            MessageRenderer renderer = context.getBean("renderer", MessageRenderer.class);
            renderer.Render();
        }
    }