关键词

spring Java eclipse bean 多例模式 prototype 懒加载 lazy-init

写在后面

• 性能简述：对于多例模式的懒加载配置是否失效的测试。
• 刚接触，摸索中，低级谬误，只是做个记录，轻喷。

（有谬误）Xml配置文件（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.xsd ">                    <!-- 对于多例模式，即使加了懒加载配置也没用 -->        <bean id="myFactoryPrototypeExample" class="instance.BeanInstanceFactory"            scope="prototype" lazy-init="false"/>                    <bean id="instanceFactoryInstancePrototypeExample" factory-bean="myFactoryPrototypeExample"             scope="prototype" lazy-init="false"/></beans>

运行的测试代码

package test;import java.util.Calendar;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import instance.BeanClass;import instance.Person;import instance.User;public class TestInstance {        //对于多例模式，默认懒加载，即使设置lazy-init="false"也有效    @Test    public void test06(){        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        System.out.println("获取对象前");        //参数是xml中待创立的对象的id        BeanClass bc3 = (BeanClass)context.getBean("instanceFactoryInstancePrototypeExample");        System.out.println(bc3+bc3.message);        }}

解决

• 思路：查看xml配置文件
• 起因：xml配置文件有误。
• 解决：最初一个bean标签少写了factory-method属性。

（正确的）Xml配置文件（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.xsd ">                    <!-- 对于多例模式，即使加了懒加载配置也没用 -->        <bean id="myFactoryPrototypeExample" class="instance.BeanInstanceFactory"            scope="prototype" lazy-init="false"/>        <!--上面这里少写了factory-method-->        <bean id="instanceFactoryInstancePrototypeExample" factory-bean="myFactoryPrototypeExample"            factory-method="createBeanClassInstance" scope="prototype" lazy-init="false"/></beans>

包构造

（补充）BeanInstanceFactory类

package instance;public class BeanInstanceFactory {        public BeanInstanceFactory(){            System.out.println("我是一个实例工厂");                    }        public BeanClass createBeanClassInstance(){            return new BeanClass("调用实例工厂办法实例化Bean");        }}

（补充）BeanClass类

package instance;public class BeanClass {    public String message;        public BeanClass() {        this.message = "构造方法实例化Bean";    }    public BeanClass(String message) {        this.message = message;    }}

运行后果

参考

org.springframework.beans.factory.BeanCreationException:No bean class specified on bean definition