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Spring之BeanFactory与ApplicationContext区别

2012-01-01 23:09 931 查看
定义两个bean分别为Bean1和Bean2

Bean1.java

package com.itmyhome.bean;

public class Bean1 {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}

}


Bean2.java

package com.itmyhome.bean;

public class Bean2 {
private String name;
private String sex;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}

}


applicationContext.xml配置文件

把Bean1和Bean2配置到xml文件中

<bean id="bean1" class="com.itmyhome.bean.Bean1">
<property name="name" value="zhangsan" />
<property name="age" value="21" />
</bean>
<!-- 此处的class路径是错误的,没有Bean3这个类 -->
<bean id="bean2" class="com.itmyhome.bean.Bean3">
<property name="name" value="lisi" />
<property name="sex" value="男" />
</bean>


进行测试

使用XmlBeanFactory

public class Client {

public static void main(String[] args) {
// TODO Auto-generated method stub
XmlBeanFactory factory = new XmlBeanFactory(new FileSystemResource("src/applicationContext.xml"));

Bean1 bean1 = (Bean1)factory.getBean("bean1");
System.out.println("bean1.name: "+bean1.getName());
System.out.println("bean1.age: "+bean1.getAge());
}
}


观察结果 可以运行通过

接下来使用ApplicationContext

public class Client {

public static void main(String[] args) {
// TODO Auto-generated method stub
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

Bean1 bean1 = (Bean1)context.getBean("bean1");
System.out.println("bean1.name: "+bean1.getName());
System.out.println("bean1.age: "+bean1.getAge());
}

}


结果报异常

Exception in thread "main" org.springframework.beans.factory.CannotLoadBeanClassException: Cannot find class [com.itmyhome.bean.Bean3] for bean with name 'bean2' defined in class path resource
[applicationContext.xml]; nested exception is java.lang.ClassNotFoundException: com.itmyhome.bean.Bean3


 

我们在applicationContext.xml中配置了两个Bean,bean1和bean2 虽然bean2中找不到Bean3这个类,但我们getBean()的时候也没有用到bean2啊,为什么会报错呢?

原因是ApplicationContext和BeanFactory提供了不同的加载机制,ApplicationContext和BeanFacotry相比,提供了更多的扩展功能,但其主要区别在于后者是延迟加载,如果Bean的某一个属性没有注入,BeanFacotry加载后,直至第一次使用调用getBean方法才会抛出异常;而ApplicationContext则在初始化自身时检验,这样有利于检查所依赖属性是否注入;所以通常情况下我们选择使用ApplicationContext.

 

解决延迟加载的办法是在applicationContext.xml中<beans>标签中添加default-lazy-init="true"属性

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd" default-lazy-init="true">


 

 

 

 

 

 

 

 

 

 

 
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