spring-扩展点-BeanFactoryPostProcessor
BeanFactoryPostProcessor:允许自定义对ApplicationContext的 bean definitions 进行修饰,扩展功能。
1、实现BeanFactoryPostProcessor 接口,会被Application contexts自动发现
2、BeanFactoryPostProcessor 仅仅对 bean definitions 发生关系,不能对bean instances 交互,对bean instances 的交互,由BeanPostProcessor的实现来处理
3、PropertyResourceConfigurer :典型实现 属性替换的功能
4、CustomEditorConfigurer :典型实现 添加自定义属性编辑器的功能
5、ConfigurationClassPostProcessor:启动@Configuration的扫描功能
举例:
有这样的也个业务场景:
<bean id="user" class="com.gym.UserServiceImpl" >
<property name="username" value="${username_}"/>
<property name="password" value="${password_}"/>
</bean>
spring支持系统对username_进行占位符的配置为properties文件配置,试想如果我们有个配置中心,我们希望spring启动的时候,从远程配置中心取数据,而非本地文件,这里就需要我们自定义一个实现BeanFactoryPostProcessor的PropertyResourceConfigurer 实例。
看下面的例子:
xml配置:
<?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"
default-autowire="byName">
<bean id="user" class="com.gym.UserServiceImpl" >
<property name="username" value="${username_}"/>
<property name="password" value="${password_}"/>
</bean>
<bean id="myFactoryPostProcessor" class="com.gym.MyFilePlaceHolderBeanFactoryPostProcessor"/>
</beans>
模拟从远程取文件:
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.core.io.support.PropertiesLoaderUtils;
/**
* @author xinchun.wang
*/
public class MyFilePlaceHolderBeanFactoryPostProcessor
extends PropertyPlaceholderConfigurer implements InitializingBean{
public void afterPropertiesSet() throws Exception {
List<Properties> list = new ArrayList<Properties>();
Properties p = PropertiesLoaderUtils.loadAllProperties("config.properties");
list.add(p);
//这里是关键,这就设置了我们远程取得的List<Properties>列表
setPropertiesArray(list.toArray(new Properties[list.size()]));
}
}
javaBean配置:
public class UserServiceImpl implements IUserService{
private static final Logger logger = LoggerFactory.getLogger(UserServiceImpl.class);
public UserServiceImpl(){
logger.info("UserServiceImpl 构造函数 ");
}
private String username;
private String password;
public String getUsername() {
return username;
}
public String getPassword() {
return password;
}
public void setUsername(String username) {
logger.info("UserServiceImpl setUsername {}",username);
this.username = username;
}
public void setPassword(String password) {
logger.info("UserServiceImpl setPassword {}",password);
this.password = password;
}
@Override
public String toString() {
return "UserServiceImpl [username=" + username + ", password="
+ password + "]";
}
}
测试:
public class TestApplicationContext {
public static void main(String[] args) {
ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
"classpath:spring/applicationContext.xml");
IUserService userService = applicationContext.getBean(IUserService.class);
String password = userService.getPassword();
applicationContext.destroy();
System.out.println(password);
}
}
------------------------------系统调用入口:------------------------------
调用入口: