SpringBoot+log4j2.xml使用application.yml属性值问题

package com.wm.dcm.utils;

import org.slf4j.MDC;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.boot.context.event.ApplicationFailedEvent;
import org.springframework.boot.context.event.ApplicationPreparedEvent;
import org.springframework.boot.context.event.ApplicationStartingEvent;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEvent;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.GenericApplicationListener;
import org.springframework.core.Ordered;
import org.springframework.core.ResolvableType;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.MutablePropertySources;
import org.springframework.core.env.PropertySource;

/**
 * @ClassName: MyApplicationStartedEventListener
 * @Description:TODO
 * @author: SUN
 * @date: 2017年9月19日 下午5:51:04
 * 
 */
public class ApplicationStartedEventListener implements GenericApplicationListener {
    
    public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 10;
    
    private static Class<?>[] EVENT_TYPES = { ApplicationStartingEvent.class,
            ApplicationEnvironmentPreparedEvent.class, ApplicationPreparedEvent.class,
            ContextClosedEvent.class, ApplicationFailedEvent.class };

    private static Class<?>[] SOURCE_TYPES = { SpringApplication.class,
            ApplicationContext.class };

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if (event instanceof ApplicationEnvironmentPreparedEvent) {

            ConfigurableEnvironment envi = ((ApplicationEnvironmentPreparedEvent) event).getEnvironment();
            MutablePropertySources mps = envi.getPropertySources();

            PropertySource<?> ps = mps.get("applicationConfigurationProperties");

            if (ps != null && ps.containsProperty("spring.kafka.bootstrap-servers")) {
                String kafkaUrl = (String) ps.getProperty("spring.kafka.bootstrap-servers");
                //System.out.println(kafkaUrl);
                MDC.put("host", kafkaUrl);
            }
            
            if (ps != null && ps.containsProperty("logging.file")) {
                String fileName = (String) ps.getProperty("logging.file");
                //System.out.println(kafkaUrl);
                MDC.put("fileName", fileName);
            }

        }

    }

    /*
     * (non-Javadoc)
     * 
     * @see org.springframework.core.Ordered#getOrder()
     */
    @Override
    public int getOrder() {
        // TODO Auto-generated method stub
        return DEFAULT_ORDER;
    }

    /*
     * (non-Javadoc)
     * 
     * @see org.springframework.context.event.GenericApplicationListener#
     * supportsEventType(org.springframework.core.ResolvableType)
     */
    @Override
    public boolean supportsEventType(ResolvableType resolvableType) {
        return isAssignableFrom(resolvableType.getRawClass(), EVENT_TYPES);
    }

    @Override
    public boolean supportsSourceType(Class<?> sourceType) {
        return isAssignableFrom(sourceType, SOURCE_TYPES);
    }

    private boolean isAssignableFrom(Class<?> type, Class<?>... supportedTypes) {
        if (type != null) {
            for (Class<?> supportedType : supportedTypes) {
                if (supportedType.isAssignableFrom(type)) {
                    return true;
                }
            }
        }
        return false;
    }
}

package com.wm.dcm.db;

import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.logging.LoggingApplicationListener;
import org.springframework.context.ApplicationListener;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.core.env.Environment;
import org.springframework.kafka.annotation.EnableKafka;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;

import com.wm.dcm.constant.LogTypeAndLevel;
import com.wm.dcm.utils.ApplicationStartedEventListener;

@SpringBootApplication
@EnableScheduling
@ComponentScan(basePackages = { "com.wm.dcm" })
@EnableKafka
@EnableAsync
public class DBApplication {
private String bootstrap;

    public String getBootstrap() {
        return bootstrap;
    }

    public void setBootstrap(String bootstrap) {
        this.bootstrap = bootstrap;
    }

    /**
     * The main method.
     *
     * @param args
     *            the arguments
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {



        // System.out.println(env);

        SpringApplication app = new SpringApplication(DBApplication.class);

        Set<ApplicationListener<?>> ls = app.getListeners();

        ApplicationStartedEventListener asel = new ApplicationStartedEventListener();

        app.addListeners(asel);
        
        app.run(args);


    }

}

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="info">
    
        <Appenders>
            <RollingFile name="RollingFile" fileName="logs/${ctx:fileName}"
                filePattern="logs/$${date:yyyy-MM}/${ctx:fileName}-%d{MM-dd-yyyy}-%i.log.gz"
                immediateFlush="true" append="true">
                <PatternLayout charset="UTF-8" pattern="[%-5p] %d[%t]  [%c] - %m%n" />

                <SizeBasedTriggeringPolicy size="50MB" />
                <!-- DefaultRolloverStrategy属性如不设置，则默认为最多同一文件夹下7个文件，这里设置了20 -->
                <DefaultRolloverStrategy max="20" />
            </RollingFile>
            <Console name="Console" target="SYSTEM_OUT">
                <PatternLayout charset="UTF-8" pattern="[%-5p] %d[%t]  [%c] - %m%n" />
            </Console>
            <Kafka name="Kafka" topic="wmdcm_log">
                <JSONLayout complete="false" compact="true" locationInfo="true" />
                
                <Property name="bootstrap.servers" value="${ctx:host}"/>
            </Kafka>
        </Appenders>


    <Loggers>
        <!-- root loggers <AppenderRef ref="Console" /> -->
        <Root level="info" includeLocation="true">
            <AppenderRef ref="RollingFile" />
            <AppenderRef ref="Console" />
            <AppenderRef ref="Kafka" />
        </Root>
        <Logger name="org.apache.kafka" level="ERROR" />
        <Logger name="org.springframework.kafka" level="ERROR" />
    </Loggers>



</Configuration>