第二章

Posted 2020-11-09 qiqi-111

工厂模式：实例化对象模式 

ref：对某个bean对象的引用

Bean的实例化三种方式：构造器实例化、静态工厂方式实例化、

一、构造器实例化

 

Beans1.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
        <!-- 通过工厂MyBean2Factory中的createBean方法实例化Bean2 -->
        <bean id="bean2" class="com.yang.static_factory.MyBean2Factory" 
                factory-method="createBean"></bean>
</beans>

Bean1.java

public class Bean1 {

}

InstanceTest1.java

public class InstanceTest1 {

    public static void main(String[] args) {
        //1.定义配置文件
        String xmlPath = "com/yang/constructor/Beans1.xml";
        //2.ApplicationContext在加载配置文件时，对bean进行实例化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
        Bean1 bean =(Bean1) applicationContext.getBean("bean1");
        System.out.println(bean);
    }
}

二、静态工厂方式实例化

 

Beans2.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
        <!-- 通过工厂MyBean2Factory中的createBean方法实例化Bean2 -->
        <bean id="bean2" class="com.yang.static_factory.MyBean2Factory" 
                factory-method="createBean"></bean>
</beans>

Bean2.java

public class Bean2 {

}

MyBean2Factory.java

public class MyBean2Factory {
    //使用自己的工厂创建bean2实例
    public static Bean2 createBean(){
        return new Bean2();
        }
}

InstanceTest2.java

public class InstanceTest2 {
    
    public static void main(String[] args) {
        //1.定义配置文件
        String xmlPath = "com/yang/static_factory/Beans2.xml";
        //2.ApplicationContext在加载配置文件时，对bean进行实例化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
        Bean2 bean =(Bean2) applicationContext.getBean("bean2");
        System.out.println(bean);
    }
}