3 Ways To Solve Java.Lang.Noclassdeffounderror Inwards Coffee J2ee
Tuesday, September 11, 2018
Add Comment
I know how frustrating is to reckon Exception inwards thread "main" java.lang.NoClassDefFoundError, which is a manifestation of NoClassDefFoundError inwards Java. I lead hold seen it a twain of times as well as spent quite a lot fourth dimension initially to figure out what is wrong, which shape is missing etc. The starting fourth dimension fault I did was mingling java.lang.ClassNotfoundException as well as NoClassDefFoundError, inwards reality, they are totally different, as well as my minute fault was using case as well as error method to solve this java.lang.NoClassDefFoundError instead of agreement why NoClassDefFoundError is coming, what is the existent argue behind NoClassDefFoundError as well as how to resolve this. In this Java tutorial, I lead hold tried to rectify that mistakes as well as uncover some secrets of NoClassDefFoundError inwards Java as well as volition part my sense some it. NoClassDefFoundError is non something which cannot hold upwards resolved or difficult to resolve it’s just its manifestation which puzzles close of Java developer. This is the close mutual error inwards Java evolution along with java.lang.OutOfMemoroyError: Java heap space as well as java.lang.OutOfMemoryError: PermGen space Anyway lets’s reckon Why NoClassDefFoundError comes inwards Java as well as what to create to resolve NoClassDefFoundError inwards Java.
What is the argue of NoClassDefFoundError inwards Java?
NoClassDefFoundError inwards Java comes when Java Virtual Machine is non able to discovery a exceptional shape at runtime which was available at compile time. For example, if nosotros lead hold a method telephone yell upwards from a shape or accessing whatever static fellow member of a Class as well as that shape is non available during run-time as well as thus JVM volition throw NoClassDefFoundError. It’s of import to sympathize that this is dissimilar than ClassNotFoundException which comes piece trying to charge a shape at run-time exclusively as well as the yell was provided during runtime, non at compile-time. Many Java developer mingles this ii Error as well as gets confused.
In short, NoClassDefFoundError volition come upwards if a shape was acquaint during compile fourth dimension but non available inwards coffee classpath during runtime. Normally you lot volition reckon below describe of piece of employment inwards log when you lot larn NoClassDefFoundError:
Exception inwards thread "main" java.lang.NoClassDefFoundError
Exception inwards thread “main” but signal that its “main” thread which is non able to discovery a exceptional shape it could hold upwards whatever thread thus just don’t worry. The divergence betwixt this error coming inwards the principal thread as well as some other thread is when Exception inwards thread “main” comes programme crashes or close itself downwards equally opposed to other thread inwards which instance your programme volition proceed to run. If you lot are actually curious as well as yell upwards that you lot sympathize how shape loading works, I advise you lot attempt some puzzles from Joshua Bloch's Java Puzzlers, it has got some actually tricky questions to evidence your knowledge.
The divergence betwixt java.lang.NoClassDefFoundError as well as ClassNotFoundException inwards Java
Many times nosotros confused ourselves with java.lang.ClassNotFoundException as well as 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 shape at runtime dynamically agency you lot laissez passer the yell of the shape at runtime as well as and thus JVM tries to charge it as well as if that shape is non flora inwards the classpath it throws java.lang.ClassNotFoundException. While inwards the instance of NoClassDefFoundError the problematic shape was acquaint during Compile fourth dimension as well as that's why the programme successfully compiled but non available during runtime for whatever reason. NoClassDefFoundError is easier to solve than ClassNotFoundException in my persuasion because hither nosotros know that Class was acquaint at construct time, but it totally depends upon environs if you lot are working inwards the J2EE environs than you lot tin larn NoClassDefFoundError fifty-fifty if the shape is acquaint because it may non hold upwards visible to the corresponding shape loader. See my post service NoClassDefFoundError vs ClassNotFoundException inwards Java for to a greater extent than details.
How to resolve java.lang.NoClassDefFoundError inwards Java
The obvious argue of NoClassDefFoundError is that a exceptional shape is non available inwards Classpath, thus nosotros necessitate to add together that into Classpath or nosotros necessitate to cheque why it’s non available inwards Classpath if nosotros are expecting it to be. There could hold upwards multiple reasons like: 2) You mightiness hold upwards running your programme using jounce ascendency as well as shape was non defined inwards manifest file's ClassPath attribute.
3) Any start-up script is overriding Classpath environs variable.
4) Because NoClassDefFoundError is a subclass of java.lang.LinkageError it tin also come upwards 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 you lot are working inwards J2EE environs than the visibility of Class alongside multiple Classloader can also drive java.lang.NoClassDefFoundError, reckon examples as well as scenario department for detailed discussion.
We volition at nowadays reckon a twain of examples as well as scenarios when java.lang.NoClassDefFoundError has come upwards earlier as well as how it's been resolved. This tin assist you lot to troubleshoot the root drive of NoClassDefFoundError inwards Java application.
NoClassDefFoundError inwards Java - Example as well as Scenarios
1. Influenza A virus subtype H5N1 uncomplicated illustration of NoClassDefFoundError is shape belongs to a missing JAR file or JAR was non added into classpath or sometimes jar's yell has been changed yesteryear mortal similar inwards my instance 1 of my colleagues has changed tibco.jar into tibco_v3.jar as well as the program is failing with java.lang.NoClassDefFoundError and I were wondering what's wrong.
2. The shape is non inwards Classpath, at that topographic point is no certain shot way of knowing it but many times you lot tin just lead hold a aspect to impress System.getproperty("java.classpath") and it volition impress the classpath from at that topographic point you lot tin at to the lowest degree larn an thought of your actual runtime classpath.
3. Just attempt to run with explicitly -classpath alternative with the classpath you lot yell upwards volition locomote as well as if it's working as well as thus it's a certain brusque sign that mortal is overriding coffee classpath.
NoClassDefFoundError inwards Java due to Exception inwards Static Initializer block
This is some other mutual argue of java.lang.NoClassDefFoundError, when your shape performs some static initialization inwards a static block similar many Singleton classes initialized itself on the static block to lead hold wages of thread-safety provided yesteryear JVM during the shape initialization process, as well as if static block throws an Exception, the shape which is referring to this shape volition larn NoclassDefFoundError inwards Java. If you lot aspect at your log file you lot should scout for whatever java.lang.ExceptionInInitializerError because that could trigger java.lang.NoClassDefFoundError: Could non initialize class on other places. Like inwards below code example, During shape loading as well as initialization User shape are throwing Exception from static initializer block, which trigger ExceptionInInitializerError during starting fourth dimension time loading of User shape inwards reply to novel User() call. Later remainder of novel User() are failing equally java.lang.NoClassDefFoundError. the province of affairs gets worst if master copy ExceptionInInitializerError, which is root drive hither is silently eaten yesteryear whatever code.
Code Example of NoClassDefFoundError due to Static block Exception:
/**
* Java programme to demonstrate how failure of static initialization afterwards cause
* java.lang.NoClassDefFoundError inwards 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 programme to demonstrate how failure of static initialization afterwards cause
* java.lang.NoClassDefFoundError inwards 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, you lot tin also larn java.lang.NoClassDefFoundError if your programme is subject on native library as well as the corresponding DLL is non there. Remember this tin also trigger java.lang.UnsatisfiedLinkError: no dll inwards java.library.path Exception Java. In lodge to solve this maintain your dll along with JAR.
6) If you lot are using ANT construct file create JAR as well as manifest file as well as thus its worth noting to debug till that degree to ensure that ANT build script is getting the right value of classpath as well as appending it to manifest.mf file.
7) Permission number on JAR file tin also drive NoClassDefFoundError inwards Java. If you lot are running your Java programme inwards a multi-user operating organization similar Linux as well as thus you lot should hold upwards using application user id for all your application resources similar JAR files, libraries, as well as configuration. If you lot are using shared library which is shared alongside multiple application which runs nether dissimilar users then you lot may run across permission issue, similar JAR file is owned yesteryear some other user as well as 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 drive NoClassDefFoundError inwards Java. As close of Java frameworks similar Spring, Struts they all role XML configuration for specifying beans. By whatever chance, if you lot seat the edible bean yell wrong, it may surface equally java.lang.NoClassDefFoundError while loading other shape which has a dependency on wrongly named bean. This is quite mutual inwards Spring MVC framework as well as Apache Struts where you lot larn tons of Exception inwards thread "main" java.lang.NoClassDefFoundError, while deploying your WAR or EAR file.
9) Another illustration of java.lang.NoClassDefFoundError, equally mentioned yesteryear our reader Nick, is that when your compiled shape which is defined inwards a package, doesn’t acquaint inwards the same bundle piece loading similar inwards the instance of JApplet it volition throw NoClassDefFoundError inwards Java. Also, reckon Nick’s comment on this error.
10) java.lang.NoClassDefFoundError can hold upwards caused due to multiple classloaders inwards J2EE environments. Since J2EE doesn’t advert measure classloader construction as well as 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 lodge to troubleshoot NoClassDefFoundError inwards J2EE application noesis of How ClassLoader industrial plant inwards Java is mandatory. Just to recap ClasLoader industrial plant on iii regulation delegation, visibility, as well as uniqueness. Delegation agency every asking to charge a shape is delegated to bring upwards classloader, visibility agency an powerfulness to flora classes loaded yesteryear the classloader, all fry classloader tin reckon classes loaded yesteryear bring upwards classloader, but bring upwards classloader tin non reckon the shape loaded yesteryear fry classloaders. Uniqueness enforce that shape loaded yesteryear the bring upwards volition never hold upwards reloaded yesteryear fry classloaders. Now suppose if a shape say User is acquaint inwards both WAR file as well as EJB-JAR file as well as loaded yesteryear WAR classloader which is fry classloader which loads the shape from EJB-JAR. When a code inwards EJB-JAR refers to this User class, Classloader which loaded all EJB shape doesn’t flora that because it was loaded yesteryear WAR classloader which is a fry of it.
This volition termination inwards java.lang.NoClassDefFoundError for User class. Also, If the shape is acquaint inwards both JAR file as well as you lot volition telephone yell upwards equals method to compare those ii object, it volition termination inwards ClassCastException equally object loaded yesteryear ii dissimilar classloaders tin non hold upwards equal.
This volition termination inwards java.lang.NoClassDefFoundError for User class. Also, If the shape is acquaint inwards both JAR file as well as you lot volition telephone yell upwards equals method to compare those ii object, it volition termination inwards ClassCastException equally object loaded yesteryear ii dissimilar classloaders tin non hold upwards equal.
11) Some of the readers of this weblog also suggested that they larn Exception inwards 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 hold upwards resolved yesteryear reinstalling JDK? IF you lot are getting this error attempt to reinstall JDK. One of our readers got this number after installing jdk1.6.0_33 as well as and thus reinstalling JDK1.6.0_25, he also has his JRE as well as JDK inwards a dissimilar folder. See his comment also yesteryear searching JDK1.6.0_33.
12) Java programme tin also throw java.lang.NoClassDefFoundError during linking which occurs during shape loading inwards Java. One of the examples of this scenario is just delete the User shape from our static initializer failure illustration after compilation as well as they attempt to run the program. This time, you lot volition larn java.lang.NoClassDefFoundError directly without java.lang.ExceptionInInitializerError and message for NoClassDefFoundError are also just printing the yell of the shape equally testing/User i.e. User shape from the testing package. Watch out for this carefully equally hither root drive 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 you lot are facing NoClassDefFoundError inwards Java and I volition guide you lot how to troubleshoot it if you lot are facing with something novel way than I listed inwards a higher house nosotros volition belike document if for the create goodness of others as well as 1 time again don’t afraid with Exception inwards thread "main" java.lang.NoClassDefFoundError.
Further Learning
Complete Java Masterclass
How to solve UnSupportedClassVersionError inwards Java
0 Response to "3 Ways To Solve Java.Lang.Noclassdeffounderror Inwards Coffee J2ee"
Post a Comment