spring：PropertyPlaceholderConfigurer用法-获取properties属性

PropertyPlaceholderConfigurer用于读取*.properties属性文件。

用法一：自动注入配置属性

在spring容器启动前，必须配置扫描用到的properties文件

<!-- 自动读取配置文件 -->
<context:property-placeholder location="classpath:*.properties"/>

接下来，创建一个spring  @Configuration

@Configuration
class MyConfig {
    @Value("${data}")
    private String data;
    public String getData() {
        return data;
    }
}

用法二：重写PropertyPlaceholderConfigurer，动态解析属性（适用于配置项不固定的场景）

组件配置：

<bean id="mailChannelConfig" class="com.bytrees.mail.ChannelConfig">
   <property name="location">
       <value>classpath:channel.properties</value>
   </property>
</bean>

show code：这个动态获取多个channel的配置

@Component
public class ChannelConfig extends PropertyPlaceholderConfigurer {
	private static Map<String, Channel> mapList = new HashMap<String, Channel>();

    public ChannelConfig() {
    }

    public Channel getChannel(String channelName) {
    	return mapList.containsKey(channelName) ? mapList.get(channelName) : null;
    }

    @Override
    protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props) throws BeansException {
        super.processProperties(beanFactoryToProcess, props);
        for (Object keySet : props.keySet()) {
            String key = keySet.toString();
            String[] keyPartArr = key.split("\\.");
            if (keyPartArr.length != 3) {
            	continue;
            }
            String channelName = keyPartArr[1];
            if (mapList.containsKey(channelName)) {
            	continue;
            }
            mapList.put(channelName, new Channel(
                props.getProperty("mail." + channelName + ".host"),
                props.getProperty("mail." + channelName + ".port"),
                props.getProperty("mail." + channelName + ".username"),
                props.getProperty("mail." + channelName + ".password"),
                props.getProperty("mail." + channelName + ".sendFrom")
            ));
        }
    }
}

参考文章：

https://www.cnblogs.com/Gyoung/p/5507063.html