java.lang.NoClassDefFoundError：无法初始化类 XXX

Question

public class PropHolder {
  public static Properties prop;

  static {
    //code for loading properties from file
  }
}

// Referencing the class somewhere else:
Properties prop = PropHolder.prop;

class PropHolder is a class of my own. The class resides in the same JAR file of the main class. So that should not because any JAR is missing from classpath.

When I look in to the JAR file by jar tf myjarfile , I can see the PropHolder.class listed there.

Btw: the code is running fine on my local machine. But couldn't work when I deploy it with some script onto a Linux server. So I think it is not the problem of the code. But for some reason. the deploy process is very hard to track.

What could be the problem?

Answer 1

My best bet is there is an issue here:

static {
    //code for loading properties from file
}

It would appear some uncaught exception occurred and propagated up to the actual ClassLoader attempting to load the class. We would need a stacktrace to confirm this though.

Either that or it occurred when creating PropHolder.prop static variable.

Answer 2

You are getting a java.lang.NoClassDefFoundError which does NOT mean that your class is missing (in that case you'd get a java.lang.ClassNotFoundException ). The ClassLoader ran into an error while reading the class definition when trying to read the class.

Put a try/catch inside your static initializer and look at the exception. If you read some files there and it differs from your local environment it's very likely the cause of the problem (maybe file can't be found, no permissions etc.).

Answer 3

NoClassDefFoundError doesn't give much of a clue as to what went wrong inside the static block. It is good practice to always have a block like this inside of static { ... } initialization code:

static {
  try {

    ... your init code here

  } catch (Throwable t) {
    LOG.error("Failure during static initialization", t);
    throw t;
  }
}

Answer 4

I had the same exception, this is how I solved the problem:

Preconditions:

1. Junit class (and test), that extended another class.

2. ApplicationContext initialized using spring, that init the project.

3. The Application context was initialized in @Before method

Solution:

Init the application context from @BeforeClass method, since the parent class also required some classes that were initialized from within the application context.

Hope this will help.

Answer 5

As mentioned above, this could be a number of things. In my case I had a statically initialized variable which relied on a missing entry in my properties file. Added the missing entry to the properties file and the problem was solved.

Answer 6

Just several days ago, I met the same question just like yours. All code runs well on my local machine, but turns out error(noclassdeffound&initialize). So I post my solution, but I don't know why, I merely advance a possibility. I hope someone know will explain this.@John Vint Firstly, I'll show you my problem. My code has static variable and static block both. When I first met this problem, I tried John Vint's solution, and tried to catch the exception. However, I caught nothing. So I thought it is because the static variable(but now I know they are the same thing) and still found nothing. So, I try to find the difference between the linux machine and my computer. Then I found that this problem happens only when several threads run in one process(By the way, the linux machine has double cores and double processes). That means if there are two tasks(both uses the code which has static block or variables) run in the same process, it goes wrong, but if they run in different processes, both of them are ok. In the Linux machine, I use

mvn -U clean  test -Dtest=path 

to run a task, and because my static variable is to start a container(or maybe you initialize a new classloader), so it will stay until the jvm stop, and the jvm stops only when all the tasks in one process stop. Every task will start a new container(or classloader) and it makes the jvm confused. As a result, the error happens. So, how to solve it? My solution is to add a new command to the maven command, and make every task go to the same container.

-Dxxx.version=xxxxx #sorry can't post more

Maybe you have already solved this problem, but still hope it will help others who meet the same problem.

Answer 7

If you're working on an Android project, make sure you aren't calling any static methods on any Android classes. I'm only using JUnit + Mockito, so maybe some other frameworks might help you avoid the problem altogether, I'm not sure.

My problem was calling Uri.parse(uriString) as part of a static initializer for a unit test. The Uri class is an Android API, which is why the unit test build couldn't find it. I changed this value to null instead and everything went back to normal.

Answer 8

I had the same exception - but only while running in debug mode, this is how I solved the problem (after 3 whole days): in the build.gradle i had : "multiDexEnabled true" set in the defaultConfig section.

        defaultConfig {
    applicationId "com.xxx.yyy"
    minSdkVersion 15
    targetSdkVersion 28
    versionCode 5123
    versionName "5123"
    // Enabling multidex support.
    multiDexEnabled true
}

but apparently this wasn't enough. but when i changed:

public class MyAppClass  extends Application 

to:

public class MyAppClass  extends MultiDexApplication 

this solved it. hope this will help someone

Answer 9

I had the same problems： java.lang.NoClassDefFoundError: Could not initialize class com.xxx.HttpUtils

static {
    //code for loading properties from file
}

it is the environment problem.That means the properties in application.yml is incorrect or empty!

Answer 10

I encounter the same problem. I inited a bean object in static block like below:

static {
    try{
        mqttConfiguration = SpringBootBeanUtils.<MqttConfiguration>getBean(MqttConfiguration.class);
    }catch (Throwable e){
        System.out.println(e);
    }
 }

Just because the process the my bean obejct inition caused a NPE, I get trouble into it. So I think you should check you static code block carefully.

Answer 11

添加这些导入语句解决了这个问题：

import org.junit.runner.RunWith;

import cucumber.api.CucumberOptions;
import cucumber.api.junit.Cucumber;