【spring bean】spring中bean的懒加载和depends-on属性设置

项目结构如下：

ResourceBean.java代码：

package com.it.res;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class ResourceBean {
    
    private FileOutputStream out;
    private File file;
    
    public void init(){
        System.out.println("初始化的方法！！！！！--->加载资源");
        try {
            this.out = new FileOutputStream(file);
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    
    public void destroy(){
        System.out.println("销毁的方法！！！--->清理内存");
        try {
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public FileOutputStream getOut(){
        return out;
    }
    
    public void setFile(File file){
        this.file=file;
    }
}

DependentBean.java代码：

package com.it.res;

import java.io.IOException;

public class DependentBean {
    ResourceBean bean;
    public void write(String ss){
        System.out.println("写入资源");
        try {
            bean.getOut().write(ss.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public void init(){
        System.out.println("depen--->初始化");
        try {
            bean.getOut().write("depen---->初始化".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public void destroy(){
        System.out.println("depen--->销毁");
        try {
            bean.getOut().write("depen--->销毁".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public ResourceBean getBean() {
        return bean;
    }

    //设置注入
    public void setBean(ResourceBean bean) {
        this.bean = bean;
    }
    
    
    
}

resWrite.xml代码：

<?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-3.0.xsd  
http://www.springframework.org/schema/context                http://www.springframework.org/schema/context/spring-context-3.0.xsd">  


    <!-- init-method  指定初始化方法，在构造器注入和setter注入完毕后执行。    destroy-method   只有“singleton”作用域能销毁，“prototype”作用域的一定不能，其他作用域不一定能    lazy-init="true"表示懒加载，不提前初始化Bean，而是只有在真正使用时才创建及初始化Bean-->
     <bean id="resourceBean" class="com.it.res.ResourceBean" init-method="init" destroy-method="destroy" lazy-init="true">
         <property name="file" value="F:/test/a.txt"> </property><!-- Spring容器能自动把字符串转换为java.io.File   -->
     </bean>
    
    <!-- 指定depends-on  则resourceBean会在dependentBean之前初始化，在dependentBean销毁之后销毁-->
    <bean id="dependentBean" class="com.it.res.DependentBean" init-method="init" destroy-method="destroy" depends-on="resourceBean">
        <property name="bean" ref="resourceBean"></property>
    </bean>
    
</beans>  

测试类Test.java代码：

package com.it.res;

import org.springframework.context.support.FileSystemXmlApplicationContext;

public class Test {
    
    @org.junit.Test
    public void testDepen(){
        FileSystemXmlApplicationContext app = new FileSystemXmlApplicationContext("resources/resWrite.xml");
        //一定要注册销毁回调，否则我们定义的销毁方法不执行
        app.registerShutdownHook();
        DependentBean bean = (DependentBean) app.getBean("dependentBean");
        bean.write("
德玛西亚
");
    }
}

测试完成，控制打印如下：

文件写入：