spring容器的懒加载

默认情况下，spring的IOC容器中lazy-init是false的，即没有打开懒加载模式。

如果你没有看到这个lazy-init 的参数设置就说明是false啦。

那么什么是懒加载？

懒加载---就是我们在spring容器启动的是先不把所有的bean都加载到spring的容器中去，而是在当需要用的时候，才把这个对象实例化到容器中。

例如我有如下的代码：

 

   

    

   
   

    

     package com.luch.spring.demo;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import org.springframework.beans.factory.annotation.Autowired;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import com.luch.spring.bean.Person;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     public 
     class NewPerson {
    
   

   

    

   
   

    
	
    
   

   

    

   
   

    
	
     @Autowired
    
   

   

    

   
   

    
	
     private Person person;
    
   

   

    

   
   

    
	
    
   

   

    

   
   

    
	
     public NewPerson(){
    
   

   

    

   
   

    

     		System.out.println(
     "lazy loading...");
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    
	
     public void printMsg(){
    
   

   

    

   
   

    
		
     if(person !=
     null) {
    
   

   

    

   
   

    

     			System.out.println(person.getName());
    
   

   

    

   
   

    

     		} 
     else {
    
   

   

    

   
   

    

     			System.out.println(
     "no person initialize!");
    
   

   

    

   
   

    

     		}
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    
	
     public void setPerson(Person person) {
    
   

   

    

   
   

    
		
     //this.person = person;
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    
	
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     }
    
   
 

在无惨构造器里输出一句话，然后我先不设置懒加载模式：我有一个beans.xml的配置文件：

 

   

    

   
   

    

     <?xml version="1.0" encoding="UTF-8"?>
    
   

   

    

   
   

    

     <beans xmlns="http://www.springframework.org/schema/beans"
    
   

   

    

   
   

    
       
     xmlns:xsi=
     "http://www.w3.org/2001/XMLSchema-instance"
    
   

   

    

   
   

    
       
     xmlns:context=
     "http://www.springframework.org/schema/context" 
    
   

   

    

   
   

    
       
     xsi:schemaLocation=
     "http://www.springframework.org/schema/beans
    
   

   

    

   
   

    

                http://www.springframework.org/schema/beans/spring-beans.xsd
    
   

   

    

   
   

    

                 http://www.springframework.org/schema/context  
    
   

   

    

   
   

    

         		http://www.springframework.org/schema/context/spring-context.xsd">
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    
		   
     <context:annotation-config/>
    
   

   

    

   
   

    
		   
     <bean id="person" class="com.luch.spring.bean.Person">
    
   

   

    

   
   

    
			   
     <property name="id" value="22">
     </property>
    
   

   

    

   
   

    
			   
     <property name="name" value="Jack">
     </property>
    
   

   

    

   
   

    
		   
     </bean>
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    
		   
     <bean id="newPerson" class="com.luch.spring.demo.NewPerson">
    
   

   

    

   
   

    
		   	   
     <property name="person" ref="person">
     </property>
    
   

   

    

   
   

    
		   
     </bean>
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    

     </beans>
    
   
 

然后我用一个junit来做测试：

 

   

    

   
   

    

     package junit.test;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import 
     static org.junit.Assert.*;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import org.junit.Test;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import org.springframework.context.support.AbstractApplicationContext;
    
   

   

    

   
   

    

     import org.springframework.context.support.ClassPathXmlApplicationContext;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     import com.luch.spring.demo.NewPerson;
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    

     public 
     class JunitTest {
    
   

   

    

   
   

    
 
    
   

   

    

   
   

    
	
     @Test
    
   

   

    

   
   

    
	
     public void printMsg(){
    
   

   

    

   
   

    

     		AbstractApplicationContext ctx = 
     new ClassPathXmlApplicationContext(
     "/beans.xml");
    
   

   

    

   
   

    
		
     //NewPerson test = (NewPerson) ctx.getBean("newPerson");
    
   

   

    

   
   

    
		
     //test.printMsg();
    
   

   

    

   
   

    

     	}
    
   

   

    

   
   

    

     }
    
   
 

这个时候输出的结果为：

四月 17, 2014 9:26:41 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@762efe5d: startup date [Thu Apr 17 21:26:41 CST 2014]; root of context hierarchy
四月 17, 2014 9:26:42 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [beans.xml]
四月 17, 2014 9:26:42 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
信息: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@77caeb3e: defining beans [org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,person,newPerson,org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor#0]; root of factory hierarchy
lazy loading..

即对象被实例化了，也就是被加载到spring的容器中去了。

然后我们设置一下懒加载模式：我们beans.xml的配置文件. lazy-init="true"即

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1. <code class="language-java"><?xml version="1.0" encoding="UTF-8"?>  
2. <beans xmlns="http://www.springframework.org/schema/beans"  
3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
4.        xmlns:context="http://www.springframework.org/schema/context"   
5.        xsi:schemaLocation="http://www.springframework.org/schema/beans  
6.            http://www.springframework.org/schema/beans/spring-beans.xsd  
7.             http://www.springframework.org/schema/context    
8.             http://www.springframework.org/schema/context/spring-context.xsd">  
9.              
10.            <context:annotation-config/>  
11.            <bean id="person" class="com.luch.spring.bean.Person">  
12.                <property name="id" value="22"></property>  
13.                <property name="name" value="Jack"></property>  
14.            </bean>  
15.              
16.            <bean id="newPerson" lazy-init="true" class="com.luch.spring.demo.NewPerson">  
17.                <property name="person" ref="person"></property>  
18.            </bean>  
19.              
20. </beans></code>  

 

   

    

   
   

    

     <?xml version=
     "1.0" encoding=
     "UTF-8"?>
    
   

   

    

   
   

    

     <beans xmlns=
     "http://www.springframework.org/schema/beans"
    
   

   

    

   
   

    

            xmlns:xsi=
     "http://www.w3.org/2001/XMLSchema-instance"
    
   

   

    

   
   

    

            xmlns:context=
     "http://www.springframework.org/schema/context" 
    
   

   

    

   
   

    

            xsi:schemaLocation=
     "http://www.springframework.org/schema/beans
    
   

   

    

   
   

    

                http://www.springframework.org/schema/beans/spring-beans.xsd
    
   

   

    

   
   

    

                 http://www.springframework.org/schema/context  
    
   

   

    

   
   

    

         		http://www.springframework.org/schema/context/spring-context.xsd">
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    

     		   <context:annotation-config/>
    
   

   

    

   
   

    

     		   <bean id=
     "person" 
     class=
     "com.luch.spring.bean.Person">
    
   

   

    

   
   

    

     			   <property name=
     "id" value=
     "22"></property>
    
   

   

    

   
   

    

     			   <property name=
     "name" value=
     "Jack"></property>
    
   

   

    

   
   

    

     		   </bean>
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    

     		   <bean id=
     "newPerson" lazy-init=
     "true" 
     class=
     "com.luch.spring.demo.NewPerson">
    
   

   

    

   
   

    

     		   	   <property name=
     "person" ref=
     "person"></property>
    
   

   

    

   
   

    

     		   </bean>
    
   

   

    

   
   

    
		   
    
   

   

    

   
   

    

     </beans>
    
   
 

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