Maven compilation fails while eclipse is successful

Question

I am using maven3.03 and Eclipse 3.5 on Windows XP. I converted old web project to be in maven configuration style.
When i compile the project in eclipse everything compile.
Note: The classpath contains: Maven Dependencies and JDK(1.6_018).
When i compile from command line using mvn, I get few errors:
1.package com.sun.xml.internal.stream.buffer.stax does not exist.
2.package com.sun.xml.internal.stream.writers does not exist
3.cannot find symbol - symbol : class XMLDOMWriterImpl
4.package com.sun.xml.internal.messaging.saaj.util does not exist
5.package com.sun.xml.internal.bind.v2.runtime.unmarshaller does not exist
6.cannot find symbol - symbol : class NamespaceContexHelper
7.cannot find symbol symbol : class ByteOutputStream

I can see that this something with sun jar. But i just can not understand why eclipse is ok and command line is not.

EDIT: One of the errors i didn't mention in the above list is:

[ERROR]<path>\EventsViewer.java:[54,69] inconvertible types found: <br>java.util.SortedMap<java.util.Date,java.util.List<com.myClass>>
required: java.util.Map<? extends java.util.Date,? extends java.util.List<com.myOtherClass>>

When i see the same line in eclipse i get warning:

Type safety: Unchecked cast from SortedMap<Date,List<myClass>> to Map<? extends Date,? extends 
 List<myOtherClass>>

In Eclipse i get warning and in maven i get error. I did check the org.eclipse.jdt.core.prefs and see the setting is org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning.

Update: I got read of some of the above errors. The "problem" is that in eclipse it appears as unused import. Stangly maven report this as error. After removing this unused import the error was gone. But still problem 3 and 7 occures

Conclusion: I guess that the warnings become errors in the javac. since I don't use any supressWarnings. I am just surprised that the error is different. What is it?

Solution 1

This is the real reason maybe from maven forum's answer

" Jerome is right that it's not recommended practice to use com.sun classes from rt.jar. And especially ones marked "internal"; you're just asking for trouble.

However I was curious about this, so tried it out. The above class can indeed be accessed by Eclipse. However compiling the code on the commandline using javac fails with the "does not exist" error. So my assumption is that Sun's java compiler detects when a special "internal" class is being accessed, and refuses to import the class. Eclipse uses a different compiler which presumably does not have this check.

Maven just uses the javac compiler available in the system execution path. Therefore the problem is nothing to do with Maven at all. It's the compiler that maven is invoking which is refusing to compile the source. I can't see any public flags in the javac commandline to disable this "blocking" of internal access, so unless you want to avoid using Sun's javac compiler you'll just have to avoid using this internal class.

Just for fun, I tried out Jerome's suggestion of putting rt.jar on the classpath: javac -cp /usr/java/jdk1.6.0_03/jre/lib/rt.jar Foo.java but that still failed to compile.

The ByteOutputStream class can be loaded at runtime via Class.forName("..").

Interestingly, a project I'm working on does happen to import class com.sun.org.apache.xml.internal.utils.SAXSourceLocator; and this works ok. Warnings are issued, but the code compiles (and yes, it's on my TODO list to fix this :-). So it's not all internal classes that are being blocked, just selected ones. "

Solution 2

Double check you are using the same JDK for both the Eclipse and Maven builds. Even if you think you are, double check again anyway.

These packages are some of the ones that are included in some versions of Java and not others.

Comments

[Omnaest]

+1 if the java version differs, adding the maven-compiler-plugin with configuration of source and target pointing towards 1.6 and updating the project configuration from the Maven project context menu will solve the problem in many cases

[Jeanne Boyarsky]

To be clear, I'm talking about the actual directory for which Java is being used rather than Java 5 vs Java 6

[Omnaest]

Ok i added it as separate answer to not confuse someone

[ronk]

thank you. I tried the maven-compiler-plugin as you wrote and it didn't help. I didn't try your second suggestion ("Update Project Configuration") (it sometimes change my .classpath in a strange way) but I will try that again and let you know. Thanks again.

[ronk]

Jeanne, I didn't understand - what do you mean in "that are included in some versions of Java and not others" and "actual directory"?

[Jeanne Boyarsky]

IBM likes to include things in their JDK that shouldn't be/aren't in the runtime. This means if you compile with the IBM JDK, things seem fine and when you compile with another JDK, classes are missing.

[ronk]

Didn't work. The strange thing is that it changes the .classpath file with J2SE_1.6 instead of eclipse that is using JDK1.6_018.