在log4j中扩展PatternLayout时出现问题

我创建了一个新类NewLinePatternLayout.java，它扩展了log4j的PatternLayout.java。 下面是我的log4j.properties。

log4j.rootLogger=INFO, R log4j.appender.R=org.apache.log4j.RollingFileAppender log4j.appender.R.File=${catalina.home}/logs/tomcat.log log4j.appender.R.MaxFileSize=10MB log4j.appender.R.MaxBackupIndex=10 log4j.appender.R.layout=com.myCompany.utils.NewLinePatternLayout log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n 

我收到如下错误：

  log4j:ERROR The class "org.apache.log4j.Layout" was loaded by log4j:ERROR [WebappClassLoader delegate: false repositories: /WEB-INF/classes/ ----------> Parent Classloader: org.apache.catalina.loader.StandardClassLoader@620a3d3b ] whereas object of type log4j:ERROR "com.myCompany.utils.NewLinePatternLayout" was loaded by [org.apache.catalina.loader.StandardClassLoader@620a3d3b]. log4j:ERROR No layout set for the appender named [R]. log4j:ERROR A "com.myCompany.utils.NewLinePatternLayout" object is not assignable to a "org.apache.log4j.Layout" variable. log4j:ERROR The class "org.apache.log4j.Layout" was loaded by log4j:ERROR [WebappClassLoader 

请告知如何解决这个问题？