Spring的三种实例化bean方式

spring提供了容器，便于替代我们管理bean对象，这容器提供了三种实例化bean的方式，下面就根据代码具体分析这三种方式

需要导入的包：spring.jar commmon-logging.jar

1，最常用的方式：构造函数实例化bean

<bean id="personService"
class="yanxi.service.impl.PersonServiceBean">

下面根据具体的代码说明这种方式

xml配置文件

<?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-2.5.xsd"> <bean id="personService" class="yanxi.service.implements.PersonServiceBean"></bean>
<!-- 构造函数实例化bean -->

springTest.java//测试单元

package junit.test;

import org.junit.BeforeClass;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import yanxi.service.PersonService;

public class SpringTest {

@BeforeClass
public static void setUpBeforeClass() throws Exception {
}

@Test public void instanceSpring(){
ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
PersonService personService = (PersonService)ctx.getBean("personService");
personService.save();
}
}

PersonServiceBean.java

package yanxi.service.implements;

import yanxi.service.PersonService;

public class PersonServiceBean implements PersonService {

public void save(){
System.out.println("我是save()方法");
}
}

PersonService.java在写java程序的时候，最好将bean实现接口，将接口包放到外部包中，规范化代码

package yanxi.service;

public interface PersonService {

public void save();

}

运行结果

我是save()方法

这种实例化bean的方式使我们用的比较多的，也是最经常用的，建议使用

2，静态工厂方法实例化

要写两个bean，一个是要实例化的bean，另一个是工厂bean。容器调用工厂bean配置项factory-method中指定的方法，在方法中实例化bean

在上面代码的基础上进行更改

更改配置xml文件

<?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-2.5.xsd"> <bean id="personService" class="yanxi.service.implements.PersonServiceBeanFactory"
factory-method="createPersonServiceBean"/>
</beans

创建PersonServiceBeanFactory.java

package yanxi.service.implements;
public class PersonServiceBeanFactory {
public static PersonServiceBean createPersonServiceBean(){
return new PersonServiceBean();
}
}

3,使用实力工厂的方法实例化bean对象

<?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-2.5.xsd"> <bean id="personServiceFactory" class="yanxi.service.implements.PersonServiceBeanFactory"/>
<bean id="personService" factory-bean="personServiceFactory" factory-method="createPersonServiceBean2"/>
</beans>

与静态工厂实例化bean的区别

public PersonServiceBean createPersonServiceBean2(){
return new PersonServiceBean();
}

一个是静态的创建bean方法，一个是重写之后的非静态的bean方法

推荐使用第一种方法