Maven Compilation Fails Impossible - Unresolved Compilation Issues

Question

I have an interesting problem with spring build webapp maven. When building inside eclipse, everything is fine, but when building through maven and deploying to the tomcat 8 webapp container, it fails to start with the following error:

Caused by: java.lang.NoClassDefFoundError: FilterConfig 

Now I tried all the obvious and well-documented dependency problems (setting up the scope provided for javax.servlet-api and importing JSP-api and making sure that they are from the latest versions, like this is a Java 8 project). I made sure that all compiler plugins have the latest versions:

War Maven Plugin 3.1.0

Maven compiler plugin 3.6.1

but the web server does not start without errors displayed on the output of the maven console. After long head scratches and painstaking comparisons between the (working) eclipse of the build and the mysteriously unsatisfactory MAW equivalent, it was found that in some of the class files generated by the MAW there were texts describing compilation problems. (From the "Open s> Text Editor" option in eclipse, the following was extracted from the .class file: some characters had to be omitted, since they would not copy correctly)

 Unresolved compilation problems: The import javax.servlet.Filter cannot be resolved The import javax.servlet.FilterChain cannot be resolved The import javax.servlet.FilterConfig cannot be resolved The import javax.servlet.ServletException cannot be resolved The import javax.servlet.ServletRequest cannot be resolved The import javax.servlet.ServletResponse cannot be resolved The import javax.servlet.http.HttpServletRequest cannot be resolved The import javax.servlet.http.HttpSession cannot be resolved Filter cannot be resolved to a type FilterConfig cannot be resolved to a type ServletException cannot be resolved to a type ServletRequest cannot be resolved to a type ServletResponse cannot be resolved to a type FilterChain cannot be resolved to a type ServletException cannot be resolved to a type HttpServletRequest cannot be resolved to a type HttpServletRequest cannot be resolved to a type HttpSession cannot be resolved to a type 

I cannot understand how the maven process succeeds and that no errors are displayed with any of the mvn goals I tried

mvn complier: compile

 [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building xxxx 2.0.1 [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ EBPP --- [INFO] Using 'UTF-8' encoding to copy filtered resources. [INFO] Copying 5 resources [INFO] [INFO] --- maven-compiler-plugin:3.6.1:compile (default-compile) @ EBPP --- [INFO] Nothing to compile - all classes are up to date [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 2.413 s [INFO] Finished at: 2017-06-28T15:11:45+01:00 [INFO] Final Memory: 9M/213M [INFO] ------------------------------------------------------------------------ 

above, but with -x showed a lot of debugging output, but did not suggest anything with compilation, in fact it claims that unresolved dependencies are defined in the class file

 ... [DEBUG] javax.servlet:javax.servlet-api:jar:3.1.0:provided [DEBUG] org.apache.velocity:velocity:jar:1.7:compile [DEBUG] commons-collections:commons-collections:jar:3.2.1:compile [DEBUG] commons-lang:commons-lang:jar:2.4:compile [DEBUG] javax.servlet.jsp:jsp-api:jar:2.2:provided ... 

mvn dependency: build-classpath

 [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building xxxx 2.0.1 [INFO] ------------------------------------------------------------------------ [INFO] [INFO] --- maven-dependency-plugin:2.8:build-classpath (default-cli) @ EBPP --- [INFO] Dependencies classpath: C:\Users\xxxxxx\.m2\repository\org\springframework\webflow\spring-webflow\2.4.5.RELEASE\spring-webflow-2.4.5.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\commons-logging\commons-logging\1.2\commons-logging-1.2.jar;C:\Users\xxxxxx\.m2\repository\opensymphony\ognl\2.6.11\ognl-2.6.11.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\webflow\spring-binding\2.4.5.RELEASE\spring-binding-2.4.5.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\webflow\spring-js\2.4.5.RELEASE\spring-js-2.4.5.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\webflow\spring-js-resources\2.4.5.RELEASE\spring-js-resources-2.4.5.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-beans\4.3.0.RELEASE\spring-beans-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-context\4.3.0.RELEASE\spring-context-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-aop\4.3.0.RELEASE\spring-aop-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-expression\4.3.0.RELEASE\spring-expression-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-web\4.3.0.RELEASE\spring-web-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-webmvc\4.3.0.RELEASE\spring-webmvc-4.3.0.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-core\4.3.9.RELEASE\spring-core-4.3.9.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\com\xxxxxxx\ebpp\JComms\2.0.1\JComms-2.0.1.jar;C:\Users\xxxxxx\.m2\repository\log4j\log4j\1.2.17\log4j-1.2.17.jar;C:\Users\xxxxxx\.m2\repository\javax\mail\mail\1.4.7\mail-1.4.7.jar;C:\Users\xxxxxx\.m2\repository\javax\activation\activation\1.1\activation-1.1.jar;C:\Users\xxxxxx\.m2\repository\org\apache\httpcomponents\httpclient\4.5.1\httpclient-4.5.1.jar;C:\Users\xxxxxx\.m2\repository\org\apache\httpcomponents\httpcore\4.4.3\httpcore-4.4.3.jar;C:\Users\xxxxxx\.m2\repository\commons-codec\commons-codec\1.9\commons-codec-1.9.jar;C:\Users\xxxxxx\.m2\repository\commons-httpclient\commons-httpclient\3.1\commons-httpclient-3.1.jar;C:\Users\xxxxxx\.m2\repository\com\xxxxxxx\ebpp\JCore\2.0.1\JCore-2.0.1.jar;C:\Users\xxxxxx\.m2\repository\javax\servlet\javax.servlet-api\3.1.0\javax.servlet-api-3.1.0.jar;C:\Users\xxxxxx\.m2\repository\org\apache\velocity\velocity\1.7\velocity-1.7.jar;C:\Users\xxxxxx\.m2\repository\commons-collections\commons-collections\3.2.1\commons-collections-3.2.1.jar;C:\Users\xxxxxx\.m2\repository\commons-lang\commons-lang\2.4\commons-lang-2.4.jar;C:\Users\xxxxxx\.m2\repository\javax\servlet\jsp\jsp-api\2.2\jsp-api-2.2.jar;C:\Users\xxxxxx\.m2\repository\junit\junit\3.8.2\junit-3.8.2.jar;C:\Users\xxxxxx\.m2\repository\org\springframework\spring-context-support\4.3.9.RELEASE\spring-context-support-4.3.9.RELEASE.jar;C:\Users\xxxxxx\.m2\repository\com\xxxxxxx\xxxxxxx\440\xxxxxxx-440.jar [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 3.331 s [INFO] Finished at: 2017-06-28T15:13:05+01:00 [INFO] Final Memory: 13M/213M [INFO] ------------------------------------------------------------------------ 

mvn validate

 [INFO] Scanning for projects... [INFO] [INFO] ------------------------------------------------------------------------ [INFO] Building xxx 2.0.1 [INFO] ------------------------------------------------------------------------ [INFO] ------------------------------------------------------------------------ [INFO] BUILD SUCCESS [INFO] ------------------------------------------------------------------------ [INFO] Total time: 0.109 s [INFO] Finished at: 2017-06-28T15:15:32+01:00 [INFO] Final Memory: 7M/213M [INFO] ------------------------------------------------------------------------ 

I'm really at a standstill. I assume maven is using a different compiler from eclipse, but I really ran out of ideas.

Has anyone else come across this before?

Thanks in advance.

Answer 1

Therefore, comparing this project with another successful project (which was converted from Java 4), the suspicion that the use of non-standard directory names was the reason for the messy behavior of mavens (when copying warSourceDirectory). I analyzed the class directory (now called) WebRoot> WEB-INF> and found that for the problem application it was full, and you already guessed that the class files were not compiled correctly! Obviously, the war plugin copied these bad files on top of the files that Maven had in the same build process that just ran successfully - hence there are no errors.

I am not sure why the bad files were there because they were not in the old Java 4 project. I suspect that they must have been created somehow during the previous failed maven build, using the wrong settings.

Answer 2

I suspect this is a combination of the eclipse building your files with compilation errors (yes, Eclipse can do this: if you never get to the non-compiled code, then you won’t even get errors), and Maven will not clear the output of Eclipse in the first place.

Maven then sees that the file is updated and does not overwrite it.

I suggest the following (to check if I am right):

• Disable Eclipse auto-build (or completely close the eclipse).
• Run the Maven target, for example package , but also run clean (i.e. mvn clean package ); the point must be 100% sure that Maven is creating these files, not Eclipse.
• Maven should now report compilation errors.

As for the error itself, it looks like you really have no dependency (but probably in the Eclipse class, not in Maven).