spring：如何用代码动态向容器中添加或移除Bean ？-白红宇

先来看一张类图：

有一个业务接口IFoo，提供了二个实现类：FooA及FooB，默认情况下，FooA使用@Component由Spring自动装配，如果出于某种原因，在运行时需要将IFoo的实现，则FooA换成FooB，可以用代码动态先将FooA的实例从容器中删除，然后再向容器中注入FooB的实例，代码如下：

1、IFoo接口：

package yjmyzz;import org.springframework.beans.factory.DisposableBean;public interface IFoo extends DisposableBean {    public void foo();}

2、 FooA实现

package yjmyzz;import org.springframework.stereotype.Component;//注：这里的名称fooA，仅仅只是为了后面演示时看得更清楚，非必需@Component("fooA")public class FooA implements IFoo {    public FooA() {        System.out.println("FooA is created!");    }    public void foo() {        System.out.println("FooA.foo()");    }    public void destroy() throws Exception {        System.out.println("FooA.destroy()");    }}

3、FooB实现

package yjmyzz;public class FooB implements IFoo {    public FooB() {        System.out.println("FooB is created!");    }    public void foo() {        System.out.println("FooB.foo()");    }    public void destroy() throws Exception {        System.out.println("FooB.destroy()");    }}

4、测试程序AppDemo

package yjmyzz;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.support.BeanDefinitionBuilder;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.beans.factory.support.DefaultListableBeanFactory;import org.springframework.context.support.AbstractRefreshableApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** * 演示在运行时，动态向容器中添加、移除Bean * author:菩提树下的杨过 http://yjmyzz.cnblogs.cm/ */public class AppDemo {    public static void main(String[] args) {        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");        //从context中取出FooA实例        IFoo f = ctx.getBean(IFoo.class);        f.foo();//FooA.foo()        //输出IFoo的Bean基本信息        System.out.println(f.getClass());//class yjmyzz.FooA        String beanName = ctx.getBeanNamesForType(IFoo.class)[0];        System.out.println(beanName);//fooA        System.out.println(ctx.isSingleton(beanName));//true        //销毁FooA实例        removeBean(ctx, beanName);        System.out.println(ctx.containsBean(beanName));//false        System.out.println("------------");        //注入新Bean        beanName = "fooB";        addBean(ctx, beanName, FooB.class);        //取出新实例        f = ctx.getBean(beanName, IFoo.class);        f.foo();        //输出IFoo的Bean基本信息        System.out.println(f.getClass());        beanName = ctx.getBeanNamesForType(IFoo.class)[0];        System.out.println(beanName);//fooB        System.out.println(ctx.isSingleton(beanName));//true        System.out.println("------------");        showAllBeans(ctx);        ctx.close();    }    /**     * 向容器中动态添加Bean     *     * @param ctx     * @param beanName     * @param beanClass     */    static void addBean(AbstractRefreshableApplicationContext ctx, String beanName, Class beanClass) {        BeanDefinitionRegistry beanDefReg = (DefaultListableBeanFactory) ctx.getBeanFactory();        BeanDefinitionBuilder beanDefBuilder = BeanDefinitionBuilder.genericBeanDefinition(beanClass);        BeanDefinition beanDef = beanDefBuilder.getBeanDefinition();        if (!beanDefReg.containsBeanDefinition(beanName)) {            beanDefReg.registerBeanDefinition(beanName, beanDef);        }    }    /**     * 从容器中移除Bean     *     * @param ctx     * @param beanName     */    static void removeBean(AbstractRefreshableApplicationContext ctx, String beanName) {        BeanDefinitionRegistry beanDefReg = (DefaultListableBeanFactory) ctx.getBeanFactory();        beanDefReg.getBeanDefinition(beanName);        beanDefReg.removeBeanDefinition(beanName);    }    /**     * 遍历输出所有Bean的信息     */    static void showAllBeans(AbstractRefreshableApplicationContext ctx) {        //遍历        for (String name : ctx.getBeanDefinitionNames()) {            System.out.println("name:" + name + ",class:" + ctx.getBean(name).getClass());        }    }}

beans.xml配置文件：

View Code

输出：

FooA is created!

FooA.foo()

class yjmyzz.FooA

fooA

true

FooA.destroy()

false

------------

FooB is created!

FooB.foo()

class yjmyzz.FooB

fooB

true

------------

name:org.springframework.context.annotation.internalConfigurationAnnotationProcessor,class:class org.springframework.context.annotation.ConfigurationClassPostProcessor

name:org.springframework.context.annotation.internalAutowiredAnnotationProcessor,class:class org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor

name:org.springframework.context.annotation.internalRequiredAnnotationProcessor,class:class org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor

name:org.springframework.context.annotation.internalCommonAnnotationProcessor,class:class org.springframework.context.annotation.CommonAnnotationBeanPostProcessor

name:org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor,class:class org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor

name:org.springframework.context.annotation.ConfigurationClassPostProcessor.enhancedConfigurationProcessor,class:class org.springframework.context.annotation.ConfigurationClassPostProcessor$EnhancedConfigurationBeanPostProcessor

name:fooB,class:class yjmyzz.FooB

FooB.destroy()