在配置spring的時候有些配置屬性放到外部檔案中進行管理或許更合理，這種情況一般是在配置資料來源的時候，將資料來源的配置資訊儲存在配置檔案中，然後在spring中載入配置檔案讀取具體的值進行bean屬性的注入，這樣更有利於管理我們的配置資訊。spring是通過一個以實現的實體bean來載入外部配置檔案：org.springframework.beans.factory.config.PropertyPlaceholderConfigurer

一下是一個簡單的例項：

配置檔案database.properties：

url=192.168.7.10
username=root
password=123
otherattr=other
 

package cn.qing.spring.bean;

public class DataBaseConfig {
	private String url;
	private String username;
	private String password;
	private String otherattr;	
	@Override
	public String toString() {
		return "DataBaseConfig [url=" + url + ", username=" + username
				+ ", password=" + password + ", otherattr=" + otherattr + "]";
	}
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getOtherattr() {
		return otherattr;
	}
	public void setOtherattr(String otherattr) {
		this.otherattr = otherattr;
	}
	
	
}
 

    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    	<property name="location" value="database.properties"/>
    </bean>
    
    <bean id="dataBaseConfig" class="cn.qing.spring.bean.DataBaseConfig">
    	<property name="url" value="${url}"/>
    	<property name="username" value="${username}"/>
    	<property name="password" value="${password}"/>
    	<property name="otherattr" value="${otherattr}"/>
    </bean>
 

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
DataBaseConfig config = (DataBaseConfig)context.getBean("dataBaseConfig");
System.out.println(config.toString());

DataBaseConfig [url=192.168.7.10, username=root, password=123, otherattr=other]