XML中的Bean作用域不起作用

Question

XML spring中的单例bean作用域不工作。只有原型工作。即使没有任何作用域，标签原型也可以工作。

XML代码片段:

<?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-3.0.xsd">
    <bean id="restaurant" class="bean_scope.Restaurant1" scope="singleton">         <!-- scope="singleton" -->
    </bean>
</beans>

setter方法的Java类:

package bean_scope;
public class Restaurant1 {
    private String welcomeNote;
    public void setWelcomeNote(String welcomeNote) {
        this.welcomeNote = welcomeNote;
    }
    public void greetCustomer(){
        System.out.println(welcomeNote);
    }   
}

Java Spring Test类:

package bean_scope;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Restaurant1Test {
    public static void main(String[] args) {
        Restaurant1 restaurantOb1=(Restaurant1) new ClassPathXmlApplicationContext("bean_scope/SpringConfig1.xml")
            .getBean("restaurant");
        restaurantOb1.setWelcomeNote("Welcome");
        restaurantOb1.greetCustomer();
        Restaurant1 restaurantOb2=(Restaurant1) new ClassPathXmlApplicationContext("bean_scope/SpringConfig1.xml")
            .getBean("restaurant");
        //restaurantOb2.setWelcomeNote("Hello");
        restaurantOb2.greetCustomer();
    }
}

输出:

 Welcome
 null

请帮助我为什么单例作用域不工作

Answer 1

由于您创建了ClassPathXmlApplicationContext的两个独立实例，因此每个实例都将拥有自己的单例bean实例。singleton作用域意味着在Spring上下文中只会有一个bean 的实例——但是在那里有两个上下文。

这将产生您期望的结果:

ApplicationContext ctx = new ClassPathXmlApplicationContext("bean_scope/SpringConfig1.xml");
Restaurant1 restaurantOb1=(Restaurant1) ctx.getBean("restaurant");
restaurantOb1.setWelcomeNote("Welcome");
restaurantOb1.greetCustomer();
Restaurant1 restaurantOb2=(Restaurant1) ctx.getBean("restaurant");
//restaurantOb2.setWelcomeNote("Hello");
restaurantOb2.greetCustomer();