3 Ways To Solve Java.Lang.Noclassdeffounderror Inwards Coffee J2ee
I know how frustrating is to reckon Exception inward thread "main" java.lang.NoClassDefFoundError, which is a manifestation of NoClassDefFoundError inward Java. I receive got seen it a dyad of times in addition to spent quite a lot fourth dimension initially to figure out what is wrong, which course of report is missing etc. The offset error I did was mingling java.lang.ClassNotfoundException in addition to NoClassDefFoundError, inward reality, they are totally different, in addition to my minute error was using lawsuit in addition to error method to solve this java.lang.NoClassDefFoundError instead of agreement why NoClassDefFoundError is coming, what is the existent argue behind NoClassDefFoundError in addition to how to resolve this. In this Java tutorial, I receive got tried to rectify that mistakes in addition to uncover some secrets of NoClassDefFoundError inward Java in addition to volition portion my sense around it. NoClassDefFoundError is non something which cannot travel resolved or difficult to resolve it’s just its manifestation which puzzles virtually of Java developer. This is the virtually mutual error inward Java evolution along with java.lang.OutOfMemoroyError: Java heap space in addition to java.lang.OutOfMemoryError: PermGen space Anyway lets’s reckon Why NoClassDefFoundError comes inward Java in addition to what to produce to resolve NoClassDefFoundError inward Java.
What is the argue of NoClassDefFoundError inward Java?
NoClassDefFoundError inward Java comes when Java Virtual Machine is non able to honor a especial course of report at runtime which was available at compile time. For example, if nosotros receive got a method telephone band from a course of report or accessing whatever static fellow member of a Class in addition to that course of report is non available during run-time in addition to thence JVM volition throw NoClassDefFoundError. It’s of import to empathise that this is dissimilar than ClassNotFoundException which comes piece trying to charge a course of report at run-time exclusively in addition to the hollo was provided during runtime, non at compile-time. Many Java developer mingles this 2 Error in addition to gets confused.
In short, NoClassDefFoundError volition come upward if a course of report was introduce during compile fourth dimension but non available inward coffee classpath during runtime. Normally yous volition reckon below business inward log when yous larn NoClassDefFoundError:
Exception inward thread "main" java.lang.NoClassDefFoundError
Exception inward thread “main” just betoken that its “main” thread which is non able to honor a especial course of report it could travel whatever thread thence just don’t worry. The deviation betwixt this error coming inward the principal thread in addition to some other thread is when Exception inward thread “main” comes plan crashes or nigh itself downwards equally opposed to other thread inward which representative your plan volition top away on to run. If yous are actually curious in addition to recollect that yous empathise how course of report loading works, I propose yous endeavor some puzzles from Joshua Bloch's Java Puzzlers, it has got some actually tricky questions to essay your knowledge.
The deviation betwixt java.lang.NoClassDefFoundError in addition to ClassNotFoundException inward Java
Many times nosotros confused ourselves with java.lang.ClassNotFoundException in addition to java.lang.NoClassDefFoundError, though both of them related to Java Classpath they are completely dissimilar to each other. ClassNotFoundException comes when JVM tries to the charge a course of report at runtime dynamically agency yous hit the hollo of the course of report at runtime in addition to and thence JVM tries to charge it in addition to if that course of report is non institute inward the classpath it throws java.lang.ClassNotFoundException. While inward the representative of NoClassDefFoundError the problematic course of report was introduce during Compile fourth dimension in addition to that's why the plan successfully compiled but non available during runtime for whatever reason. NoClassDefFoundError is easier to solve than ClassNotFoundException in my sentiment because hither nosotros know that Class was introduce at create time, but it totally depends upon surround if yous are working inward the J2EE surround than yous tin larn NoClassDefFoundError fifty-fifty if the course of report is introduce because it may non travel visible to the corresponding course of report loader. See my shipping service NoClassDefFoundError vs ClassNotFoundException inward Java for to a greater extent than details.
How to resolve java.lang.NoClassDefFoundError inward Java
The obvious argue of NoClassDefFoundError is that a especial course of report is non available inward Classpath, thence nosotros quest to add together that into Classpath or nosotros quest to banking concern check why it’s non available inward Classpath if nosotros are expecting it to be. There could travel multiple reasons like: 2) You powerfulness travel running your plan using jounce ascendence in addition to course of report was non defined inward manifest file's ClassPath attribute.
3) Any start-up script is overriding Classpath surround variable.
4) Because NoClassDefFoundError is a subclass of java.lang.LinkageError it tin also come upward if 1 of it dependency similar native library may non available.
4) Check for java.lang.ExceptionInInitializerError in your log file. NoClassDefFoundError due to the failure of static initialization is quite common.
5) If yous are working inward J2EE surround than the visibility of Class with multiple Classloader can also travail java.lang.NoClassDefFoundError, reckon examples in addition to scenario department for detailed discussion.
We volition at nowadays reckon a dyad of examples in addition to scenarios when java.lang.NoClassDefFoundError has come upward earlier in addition to how it's been resolved. This tin aid yous to troubleshoot the root travail of NoClassDefFoundError inward Java application.
NoClassDefFoundError inward Java - Example in addition to Scenarios
1. Influenza A virus subtype H5N1 uncomplicated representative of NoClassDefFoundError is course of report belongs to a missing JAR file or JAR was non added into classpath or sometimes jar's hollo has been changed yesteryear mortal similar inward my representative 1 of my colleagues has changed tibco.jar into tibco_v3.jar in addition to the program is failing with java.lang.NoClassDefFoundError and I were wondering what's wrong.
2. The course of report is non inward Classpath, at that spot is no certain shot way of knowing it but many times yous tin just receive got a aspect to impress System.getproperty("java.classpath") and it volition impress the classpath from at that spot yous tin at to the lowest degree larn an thought of your actual runtime classpath.
3. Just endeavor to run with explicitly -classpath pick with the classpath yous recollect volition operate in addition to if it's working in addition to thence it's a certain brusque sign that mortal is overriding coffee classpath.
NoClassDefFoundError inward Java due to Exception inward Static Initializer block
This is some other mutual argue of java.lang.NoClassDefFoundError, when your course of report performs some static initialization inward a static block similar many Singleton classes initialized itself on the static block to accept payoff of thread-safety provided yesteryear JVM during the course of report initialization process, in addition to if static block throws an Exception, the course of report which is referring to this course of report volition larn NoclassDefFoundError inward Java. If yous aspect at your log file yous should sentinel for whatever java.lang.ExceptionInInitializerError because that could trigger java.lang.NoClassDefFoundError: Could non initialize class on other places. Like inward below code example, During course of report loading in addition to initialization User course of report are throwing Exception from static initializer block, which trigger ExceptionInInitializerError during offset fourth dimension loading of User course of report inward reply to novel User() call. Later residual of novel User() are failing equally java.lang.NoClassDefFoundError. the province of affairs gets worst if master ExceptionInInitializerError, which is root travail hither is silently eaten yesteryear whatever code.
Code Example of NoClassDefFoundError due to Static block Exception:
/**
* Java plan to demonstrate how failure of static initialization afterward cause
* java.lang.NoClassDefFoundError inward Java.
* @author Javin Paul
*/
public class NoClassDefFoundErrorDueToStaticInitFailure {
public static void main(String args[]){
List<User> users = new ArrayList<User>(2);
for(int i=0; i<2; i++){
try{
users.add(new User(String.valueOf(i))); //will throw NoClassDefFoundError
}catch(Throwable t){
t.printStackTrace();
}
}
}
}
class User{
private static String USER_ID = getUserId();
public User(String id){
this.USER_ID = id;
}
private static String getUserId() {
throw new RuntimeException("UserId Not found");
}
}
* Java plan to demonstrate how failure of static initialization afterward cause
* java.lang.NoClassDefFoundError inward Java.
* @author Javin Paul
*/
public class NoClassDefFoundErrorDueToStaticInitFailure {
public static void main(String args[]){
List<User> users = new ArrayList<User>(2);
for(int i=0; i<2; i++){
try{
users.add(new User(String.valueOf(i))); //will throw NoClassDefFoundError
}catch(Throwable t){
t.printStackTrace();
}
}
}
}
class User{
private static String USER_ID = getUserId();
public User(String id){
this.USER_ID = id;
}
private static String getUserId() {
throw new RuntimeException("UserId Not found");
}
}
Output
java.lang.ExceptionInInitializerError
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
Caused by: java.lang.RuntimeException: UserId Not found
at testing.User.getUserId(NoClassDefFoundErrorDueToStaticInitFailure.java:41)
at testing.User.<clinit>(NoClassDefFoundErrorDueToStaticInitFailure.java:35)
... 1 more
java.lang.NoClassDefFoundError: Could non initialize class testing.User
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
java.lang.ExceptionInInitializerError
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
Caused by: java.lang.RuntimeException: UserId Not found
at testing.User.getUserId(NoClassDefFoundErrorDueToStaticInitFailure.java:41)
at testing.User.<clinit>(NoClassDefFoundErrorDueToStaticInitFailure.java:35)
... 1 more
java.lang.NoClassDefFoundError: Could non initialize class testing.User
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
5) Since NoClassDefFoundError is an also a LinkageError which arises due to dependency on some other class, yous tin also larn java.lang.NoClassDefFoundError if your plan is subject on native library in addition to the corresponding DLL is non there. Remember this tin also trigger java.lang.UnsatisfiedLinkError: no dll inward java.library.path Exception Java. In social club to solve this hold your dll along with JAR.
6) If yous are using ANT create file create JAR in addition to manifest file in addition to thence its worth noting to debug till that degree to ensure that ANT build script is getting the right value of classpath in addition to appending it to manifest.mf file.
7) Permission number on JAR file tin also travail NoClassDefFoundError inward Java. If yous are running your Java plan inward a multi-user operating arrangement similar Linux in addition to thence yous should travel using application user id for all your application resources similar JAR files, libraries, in addition to configuration. If yous are using shared library which is shared with multiple application which runs nether dissimilar users then yous may run across permission issue, similar JAR file is owned yesteryear some other user in addition to non accessible to your application. One of our reader “it’s me said”, faced java.lang.NoClassDefFoundError due to this reason. See his comment also.
8) Typo on XML Configuration tin also travail NoClassDefFoundError inward Java. As virtually of Java frameworks similar Spring, Struts they all purpose XML configuration for specifying beans. By whatever chance, if yous pose the edible bean hollo wrong, it may surface equally java.lang.NoClassDefFoundError while loading other course of report which has a dependency on wrongly named bean. This is quite mutual inward Spring MVC framework in addition to Apache Struts where yous larn tons of Exception inward thread "main" java.lang.NoClassDefFoundError, while deploying your WAR or EAR file.
9) Another representative of java.lang.NoClassDefFoundError, equally mentioned yesteryear our reader Nick, is that when your compiled course of report which is defined inward a package, doesn’t introduce inward the same packet piece loading similar inward the representative of JApplet it volition throw NoClassDefFoundError inward Java. Also, reckon Nick’s comment on this error.
10) java.lang.NoClassDefFoundError can travel caused due to multiple classloaders inward J2EE environments. Since J2EE doesn’t advert measure classloader construction in addition to it depends on dissimilar vendors similar Tomcat, WebLogic, WebSphere on how they charge dissimilar components of J2EE similar WAR file or EJB-JAR file. In social club to troubleshoot NoClassDefFoundError inward J2EE application noesis of How ClassLoader plant inward Java is mandatory. Just to recap ClasLoader plant on 3 regulation delegation, visibility, in addition to uniqueness. Delegation agency every asking to charge a course of report is delegated to rear classloader, visibility agency an powerfulness to institute classes loaded yesteryear the classloader, all tike classloader tin reckon classes loaded yesteryear rear classloader, but rear classloader tin non reckon the course of report loaded yesteryear tike classloaders. Uniqueness enforce that course of report loaded yesteryear the rear volition never travel reloaded yesteryear tike classloaders. Now suppose if a course of report say User is introduce inward both WAR file in addition to EJB-JAR file in addition to loaded yesteryear WAR classloader which is tike classloader which loads the course of report from EJB-JAR. When a code inward EJB-JAR refers to this User class, Classloader which loaded all EJB course of report doesn’t institute that because it was loaded yesteryear WAR classloader which is a tike of it.
This volition effect inward java.lang.NoClassDefFoundError for User class. Also, If the course of report is introduce inward both JAR file in addition to yous volition telephone band equals method to compare those 2 object, it volition effect inward ClassCastException equally object loaded yesteryear 2 dissimilar classloaders tin non travel equal.
This volition effect inward java.lang.NoClassDefFoundError for User class. Also, If the course of report is introduce inward both JAR file in addition to yous volition telephone band equals method to compare those 2 object, it volition effect inward ClassCastException equally object loaded yesteryear 2 dissimilar classloaders tin non travel equal.
11) Some of the readers of this weblog also suggested that they larn Exception inward thread "main" java.lang.NoClassDefFoundError: com/sun/tools/javac/Main , this error agency either your Classpath, PATH or JAVA_HOME is non setup properly or JDK installation is non correct. which tin travel resolved yesteryear reinstalling JDK? IF yous are getting this error endeavor to reinstall JDK. One of our readers got this number after installing jdk1.6.0_33 in addition to and thence reinstalling JDK1.6.0_25, he also has his JRE in addition to JDK inward a dissimilar folder. See his comment also yesteryear searching JDK1.6.0_33.
12) Java plan tin also throw java.lang.NoClassDefFoundError during linking which occurs during course of report loading inward Java. One of the examples of this scenario is just delete the User course of report from our static initializer failure representative after compilation in addition to they endeavor to run the program. This time, yous volition larn java.lang.NoClassDefFoundError directly without java.lang.ExceptionInInitializerError and message for NoClassDefFoundError are also just printing the hollo of the course of report equally testing/User i.e. User course of report from the testing package. Watch out for this carefully equally hither root travail is absent of User.class file.
java.lang.NoClassDefFoundError: testing/User
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
at testing.NoClassDefFoundErrorDueToStaticInitFailure.main(NoClassDefFoundErrorDueToStaticInitFailure.java:23)
Let me know how precisely yous are facing NoClassDefFoundError inward Java and I volition guide yous how to troubleshoot it if yous are facing with something novel way than I listed inward a higher house nosotros volition belike document if for the produce goodness of others in addition to over again don’t afraid with Exception inward thread "main" java.lang.NoClassDefFoundError.
Further Learning
Complete Java Masterclass
How to solve UnSupportedClassVersionError inward Java
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