spring容器的懒加载lazy-init设置

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

<?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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spring容器的懒加载lazy-init设置

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