Ant失败：线程“main”中的异常java.lang.NoClassDefFoundError org / apache / tools / ant / launch / Launcher

Question

I'm on Fedora 17. I am trying to compile a project with an ant build file which is not compatible with Java 7. So I decided to install OpenJDK 6. JDK 6 is unfortunately removed from yum repositories, and I figured it would be easy to install it manually. I learned that there is no JAVA_HOME variable and alternatives system is used instead. So I downloaded OpenJDK binaries (from OSG if it matters) and installed java & javac & javaws using alternatives --install command. Checking java --version and javac --version proved it to be successful. But the strange thing happened is that ant is not working any more! When I type ant --execdebug I receive this message:

exec "/usr/lib/jvm/openjdk-6.0.24/bin/java" -classpath "/usr/bin/build-classpath: 
error: JVM_LIBDIR /usr/lib/jvm-exports/openjdk-6.0.24 does not exist or is not a 
directory:/usr/bin/build-classpath: error: JVM_LIBDIR /usr/lib/jvm-exports/openjdk-6.0.24 
does not exist or is not a directory:/usr/lib/jvm/openjdk-6.0.24/lib/tools.jar"
-Dant.home="/usr/share/ant" -Dant.library.dir="/usr/share/ant/lib" 
org.apache.tools.ant.launch.Launcher -cp ""
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/tools/ant/launch/Launcher
Caused by: java.lang.ClassNotFoundException: org.apache.tools.ant.launch.Launcher
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: org.apache.tools.ant.launch.Launcher. Program will exit.

As the case with java, there is no ANT_HOME variable too. But there wasn't an ANT_HOME even before installing java 6 while it was working fine. Ant is installed under /usr/bin/ant that's already in PATH.

UPDATE: I know there are similar questions qustion 1 , question 2 . But neither resolved my problem. For example adding ANT_HOME=/usr/bin deteriorates the situation, in that ant is not working even with JDK 7! Due to my unfamiliarity with alternatives system, I totally removed java related alternatives, added JAVA_HOME, and modified PATH instead. Again, java & javac are working fine, with java --version returning the right version, but ant is returning the same error. As the --execdebug tells us, JVM_LIBDIR is not pointing to the right location. I suppose that the value is set in java.conf file, so I'm pasting it here (I've installed JDK 6 & 7 on /usr/lib/jvm):

# System-wide Java configuration file                                -*- sh -*-
#
# JPackage Project <http://www.jpackage.org/>

# Location of jar files on the system
JAVA_LIBDIR=/usr/share/java

# Location of arch-specific jar files on the system
JNI_LIBDIR=/usr/lib64/java

# Location for noarch jar files using arch-specifics jar files
JAVAJNI_LIBDIR=/usr/share/java-jni

# Root of all JVM installations
JVM_ROOT=/usr/lib/jvm

# You can define a system-wide JVM root here if you're not using the
# default one.
#
# If you have the a base JRE package installed
# (e.g. java-1.6.0-openjdk):
#JAVA_HOME=$JVM_ROOT/jre
#
# If you have the a devel JDK package installed
# (e.g. java-1.6.0-openjdk-devel):
#JAVA_HOME=$JVM_ROOT/java-1.7.0-openjdk-1.7.0.9.x86_64
JAVA_HOME=$JVM_ROOT/openjdk-6.0.24

# Options to pass to the java interpreter
JAVACMD_OPTS=

By just commenting and uncommenting the corresponding lines in java.conf, it turns that ant is working fine with 7 and fails with 6. when I echo JVM_LIBDIR just before java command in the ant shell, I receive user/share/java as stated in java.conf. But ant --execdebug has returned something strange: JVM_LIBDIR /usr/lib/jvm-exports/openjdk-6.0.24 . What is that and how can I fix it?

If you could not tell the problem here, what is the neatest and safest way to install multiple versions of JDK, that can be switched easily?

Any help is well appreciated.

Answer 1

You are missing a jar on the classpath. Make sure you have all the required libraries in the lib folder from which ant is picking up the dependencies.

Check this similar question.

Answer 2

I can only answer the last question.

WE DO NOT USE THE ALTERNATIVE SYSTEM, instead, we manage it manually.

What we do in both Ubuntu and CentOS is that we always use the tar.gz from Oracle JDK website, extract it to a subfolder in /opt (like /opt/jdk_1.7.0_09 ), make a symbol link to the folder (like /opt/default_jdk -> /opt/jdk_1.7.0_09 ), and set the environment varibles where we point JAVA_HOME to the symbol link rather than the actual folder ( JAVA_HOME=/opt/default_jdk ).

In this way, if we want to change or update the jdk (eg from JDK 7 upadte 9 to JDK 7 upadte 15), we just download the tar.gz package, extract it to another folder (eg /opt/jdk_1.7.0_15 ), delete the old symbol link (which points to /opt/jdk_1.7.0_09 ) and create a new one pointing to the new folder (eg /opt/default_jdk -> /opt/jdk_1.7.0_15 ).

Same way works with 32 and 64 bit jdks, different versions of Ant, Maven, Gradle, etc.

Answer 3

Looks like something is wrong with your Java installation. Refer this http://www.linuxforums.org/forum/red-hat-fedora-linux/151698-problems-tomcat.html with a similar issue which got resolved later.