title: Logback and Spring Boot's new springProperty lookup mechanism not working
body: <p>I'm using Spring Boot 1.3.0.RC1 through spring-cloud Brixton.M2 and have been unable to pull spring boot properties into logback.xml as implied by this feature checkin <a href="https://github.com/spring-projects/spring-boot/commit/055ace37f006120b0006956b03c7f358d5f3729f" rel="nofollow noreferrer">Support springProperty in logback configurations</a> </p>
  
  <p>I'm using .yml files and want to pull application name out of bootstrap.yml or application.yml.</p>
  
  <p>logback-spring.xml:</p>
  
  <pre><code>&lt;configuration&gt;
        &lt;springProperty scope="context" name="myappName" source="spring.application.name"/&gt;
        &lt;contextName&gt;${myappName}&lt;/contextName&gt;
        &lt;appender name="logFileAppender" class="ch.qos.logback.core.rolling.RollingFileAppender"&gt;
           &lt;file&gt;logs/${myappName}.log&lt;/file&gt;
           ... 
        &lt;/appender&gt;
        ...
  &lt;/configuration&gt;
  </code></pre>
  
  <p>The documentation here <a href="https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#environment-properties" rel="nofollow noreferrer">Spring Boot Logback extensions</a> doesn't help much.</p>
  
  <p>This other stackoverflow question <a href="https://stackoverflow.com/questions/29322709/unable-to-use-spring-property-placeholders-in-logback-xml">Unable to use Spring Property Placeholders in logback.xml</a> is older and doesnt work for me either.   Any insight would be helpful. </p>
  
  <p>Per request, here is the relevant dependency tree that is being used</p>
  
  <pre><code>[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:1.3.0.RC1:compile
  [INFO] |  +- org.springframework.boot:spring-boot-starter:jar:1.3.0.RC1:compile
  [INFO] |  |  +- org.springframework.boot:spring-boot:jar:1.3.0.RC1:compile
  [INFO] |  |  +- org.springframework.boot:spring-boot-autoconfigure:jar:1.3.0.RC1:compile
  [INFO] |  |  +- org.springframework.boot:spring-boot-starter-logging:jar:1.3.0.RC1:compile
  [INFO] |  |  |  +- ch.qos.logback:logback-classic:jar:1.1.3:compile
  [INFO] |  |  |  |  \- ch.qos.logback:logback-core:jar:1.1.3:compile
  [INFO] |  |  |  +- org.slf4j:jcl-over-slf4j:jar:1.7.12:compile
  [INFO] |  |  |  +- org.slf4j:jul-to-slf4j:jar:1.7.12:compile
  [INFO] |  |  |  \- org.slf4j:log4j-over-slf4j:jar:1.7.12:compile
  [INFO] |  |  \- org.yaml:snakeyaml:jar:1.16:runtime
  </code></pre>
  
  <p>Per 2nd request for info, what is actually going on is that logback property <em>myappName</em> does not get a value.  The way I know this is that the value becomes "myappName_IS_UNDEFINED" and my logfile gets named "myappName_IS_UNDEFINED.log" and the %contextName is set to "myappName_IS_UNDEFINED".</p>