Spring-depends on

depends-on用来表示一个bean A的实例化依靠另一个bean B的实例化， 但是A并不需要持有一个B的对象，如果需要的话就不用depends-on。

示例：

　　步骤一：

public class SystemSettings {
    public static int SESSION_TIMEOUT = 30;
    public static int REFRESH_CYCLE = 60;
}

步骤二：

package org.hope.spring.bean.dependon;

public class SysInit {
    public SysInit() {
        System.out.println("SysInit");
        //模拟从数据库中加载系统设置信息
        SystemSettings.REFRESH_CYCLE = 100;
        SystemSettings.SESSION_TIMEOUT = 10;
    }
}

步骤三：

package org.hope.spring.bean.dependon;

import java.util.Timer;
import java.util.TimerTask;

public class CacheManager {
    public CacheManager() {
        Timer timer = new Timer();
        TimerTask cacheTask = new CacheTask();

        timer.schedule(cacheTask, 0, SystemSettings.REFRESH_CYCLE * 1000);
    }

    public void cycle() {
        System.out.println("初始值:" + SystemSettings.REFRESH_CYCLE);
    }
}

步骤四：

<bean id="sysInit" class="org.hope.spring.bean.dependon.SysInit"/>
<bean id="manager" class="org.hope.spring.bean.dependon.CacheManager" depends-on="sysInit"/>

步骤五：

package org.hope.spring.bean.dependon;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"classpath:bean3.xml"})
public class DependOnTest {
    @Autowired
    private CacheManager manager;

    @Test
    public void test() {
        manager.cycle();
    }
}

结果：

初始值:100

结论:

sysInt先去manager实例化。

https://gitee.com/huayicompany/spring-learn/tree/master/spring-bean

参考：

[1] 《精通Spring4.x企业应用开发实战》，电子工业出版社，陈雄华