Bean作用域实例

1.单例

<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-2.5.xsd">

       <bean id="customerService" 
            class="com.yiibai.customer.services.CustomerService" />
        
</beans>

执行结果：

package com.yiibai.common;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.yiibai.customer.services.CustomerService;

public class App 
{
    public static void main( String[] args )
    {
        ApplicationContext context = 
         new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});

        CustomerService custA = (CustomerService)context.getBean("customerService");
        custA.setMessage("Message by custA");
        System.out.println("Message : " + custA.getMessage());
        
        //retrieve it again
        CustomerService custB = (CustomerService)context.getBean("customerService");
        System.out.println("Message : " + custB.getMessage());
    }
}

输出结果：

Message : Message by custA
Message : Message by custA 

2.原型

在原型作用域，必须为每个 getBean()方法中调用返回一个新的实例。

<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-2.5.xsd">

   <bean id="customerService" class="com.yiibai.customer.services.CustomerService" 
         scope="prototype"/>
        
</beans>

3. Bean作用域注释

注释来定义 bean 的作用域

package com.yiibai.customer.services;

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
@Scope("prototype")
public class CustomerService 
{
    String message;
    
    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

启用自动组件扫描

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-2.5.xsd">

       <context:component-scan base-package="com.yiibai.customer" />
        
</beans>