Spring之BeanFactory与ApplicationContext区别详解编程语言

定义两个bean分别为Bean1和Bean2

Bean1.java

package com.blog.ytso.com.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.blog.ytso.com.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.blog.ytso.com.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.blog.ytso.com.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.blog.ytso.com.bean.Bean3] for bean with name 'bean2' defined in class path resource 

[applicationContext.xml]; nested exception is java.lang.ClassNotFoundException: com.blog.ytso.com.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">