java工厂模式读取配置文件*.properties信息-蒲公英云

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();
    }
}