tomcat 클래스 로드 순서
Tomcat 에서 ClassLoader 의 상하구조는 다음 그림과 같습니다.
 | | |
| Bootstrap
|
System
|
Common
/ \
Catalina Shared
/ \
Webapp1 Webapp2 ...
| |
| | |
그런데 class 를 찾는 순서는 Tomcat version 에 따라 순서가 다르다는 것을 발견했습니다.
Tomcat 4.x Class 를 찾는 순서
- /WEB-INF/classes of your web application
- /WEB-INF/lib/*.jar of your web application
- Bootstrap classes of your JVM
- System class loader classses (described above)
- $CATALINA_HOME/common/classes
- $CATALINA_HOME/common/endorsed/*.jar
- $CATALINA_HOME/common/lib/*.jar
- $CATALINA_HOME/shared/classes
- $CATALINA_HOME/shared/lib/*.jar
Tomcat 5.x Class 를 찾는 순서
- Bootstrap classes of your JVM
- System class loader classses (described above)
- /WEB-INF/classes of your web application
- /WEB-INF/lib/*.jar of your web application
- $CATALINA_HOME/common/classes
- $CATALINA_HOME/common/endorsed/*.jar
- $CATALINA_HOME/common/lib/*.jar
- $CATALINA_BASE/shared/classes
- $CATALINA_BASE/shared/lib/*.jar
문제는 환경변수에 CLASSPATH 로 설정된 jar 와 context 의 WEB-INF/lib 밑의 jar 중에서 어떤 jar 를 먼저 찾는가 입니다.
CLASSPATH 에서 jar 를 읽어오는 ClassLoader 는 System class loader 입니다.
따라서 4.x 에서는 WEB-INF/lib 밑의 jar 가 CLASSPATH 로 설정된 jar 보다 먼저 읽히고
5.x 에서는 CLASSPATH 로 설정된 jar 가 WEB-INF/lib 밑의 jar 보다 먼저 읽힙니다.
Tomcat 의 ClassLoader 에 대해서는 아래 문서를 보시라.
http://jakarta.apache.org/tomcat/tomcat-5.0-doc/class-loader-howto.html
출처 - http://blog.daum.net/cjsxowls/11338538
===================================================================================
Tomcat5.5 클래스 로딩 순서
Bootstrap classes of your JVM
System class loader classses (described above)
/WEB-INF/classes of your web application
/WEB-INF/lib/*.jar of your web application
$CATALINA_HOME/common/classes
$CATALINA_HOME/common/endorsed/*.jar
$CATALINA_HOME/common/i18n/*.jar
$CATALINA_HOME/common/lib/*.jar
$CATALINA_BASE/shared/classes
$CATALINA_BASE/shared/lib/*.jar
Tomcat5.0 클래스로딩 순서
Bootstrap classes of your JVM
System class loader classses (described above)
/WEB-INF/classes of your web application
/WEB-INF/lib/*.jar of your web application
$CATALINA_HOME/common/classes
$CATALINA_HOME/common/endorsed/*.jar
$CATALINA_HOME/common/lib/*.jar
$CATALINA_BASE/shared/classes
$CATALINA_BASE/shared/lib/*.jar
Tomcat4.1 클래스로딩 순서
/WEB-INF/classes of your web application
/WEB-INF/lib/*.jar of your web application
Bootstrap classes of your JVM
System class loader classses (described above)
$CATALINA_HOME/common/classes
$CATALINA_HOME/common/endorsed/*.jar
$CATALINA_HOME/common/lib/*.jar
$CATALINA_BASE/shared/classes
$CATALINA_BASE/shared/lib/*.jar