package DbPackage;

//这是普通bean，可以通过占位符的方式使用属性占位符适配器已经配置好的属性值
public class Db {
    private String driver;
    private String url;
    private String user;
    private String  pass;

    public void setDriver(String driver) {
        this.driver = driver;
    }

    public String getDriver() {
        return driver;
    }

    public String getUrl() {
        return url;
    }

    public String getUser() {
        return user;
    }

    public String getPass() {
        return pass;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public void setPass(String pass) {
        this.pass = pass;
    }



}

package TestPackage;

import DbPackage.Db;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
//测试类
public class SpringTest {
    public static void main(String []args){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");
        Db db =  applicationContext.getBean("dataSource", Db.class);
        System.out.println(db.getDriver());

    }
}

<?xml version="1.0" encoding="GBK"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">

    <!--这就是属性占位符适配器，无需指定id。实现类是PropertyPlaceholderConfigurer-->
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>dbconn.properties</value>
            </list>
        </property>
    </bean>

<!--通过占位符的方式获得相应的值，注意名字要写对-->
    <bean id="dataSource" class="DbPackage.Db"
          p:driver="${driver}"
          p:url="${url}"
          p:user="${user}"
          p:pass="${driver}"

    />


</beans>

driver =  com.microsoft.sqlserver.jdbc.SQLServerDriver
url = jdbc:sqlserver://localhost:1433; DatabaseName=homework_Submit_System
user =  root
pass = 123456

这是我看李刚编著的《轻量级javaEE企业应用实战（第五版）-Struts2+Spring5+Hibernate5/JAP2》后总结出来的。