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从 JVM 分析 hibernate-validator NoClassDefFoundError

运维开发网 https://www.qedev.com 2020-02-22 12:27 出处:51CTO 作者:UMUTech
最近排查一个springboot应用抛出hibernate.validatorNoClassDefFoundError的问题,异常信息如下:Causedby:java.lang.NoClassDefFoundError:Couldnotinitializeclassorg.hibernate.validator.internal.engine.ConfigurationImplatorg.hibe

最近排查一个spring boot应用抛出hibernate.validator NoClassDefFoundError的问题,异常信息如下:

Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.hibernate.validator.internal.engine.ConfigurationImpl

at org.hibernate.validator.HibernateValidator.createGenericConfiguration(HibernateValidator.java:33) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]

at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:276) ~[validation-api-1.1.0.Final.jar:na]

at org.springframework.boot.validation.MessageInterpolatorFactory.getObject(MessageInterpolatorFactory.java:53) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]

at org.springframework.boot.autoconfigure.validation.DefaultValidatorConfiguration.defaultValidator(DefaultValidatorConfiguration.java:43) ~[spring-boot-autoconfigure-1.5.3.RELEASE.jar:1.5.3.RELEASE]

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_112]

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_112]

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_112]

at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_112]

at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162) ~[spring-beans-4.3.8.RELEASE.jar:4.3.8.RELEASE]

... 32 common frames omitted

这个错误信息表面上是 NoClassDefFoundError ,但是实际上 ConfigurationImpl这个类是在 hibernate-validator-5.3.5.Final.jar 里的,不应该出现找不到类的情况。

那为什么应用里抛出这个 NoClassDefFoundError ?

有经验的开发人员从 Could not initialize class 这个信息就可以知道,实际上是一个类在初始化时抛出的异常,比如static的静态代码块,或者static字段初始化的异常。

谁初始化了 org.hibernate.validator.internal.engine.ConfigurationImpl

但是当我们在 HibernateValidator 这个类,创建 ConfigurationImpl 的代码块里打断点时,发现有两个线程触发了断点:

public class HibernateValidator implements ValidationProvider<HibernateValidatorConfiguration> [email protected]
br/>@Override
return new ConfigurationImpl( state );

}

其中一个线程的调用栈是:

Thread [background-preinit] (Class load: ConfigurationImpl)

HibernateValidator.createGenericConfiguration(BootstrapState) line: 33

Validation$GenericBootstrapImpl.configure() line: 276

BackgroundPreinitializer$ValidationInitializer.run() line: 107

BackgroundPreinitializer$1.runSafely(Runnable) line: 59

BackgroundPreinitializer$1.run() line: 52

Thread.run() line: 745

另外一个线程调用栈是:

Thread [main] (Suspended (breakpoint at line 33 in HibernateValidator))

owns: ConcurrentHashMap<K,V> (id=52)

owns: Object (id=53)

HibernateValidator.createGenericConfiguration(BootstrapState) line: 33

Validation$GenericBootstrapImpl.configure() line: 276

MessageInterpolatorFactory.getObject() line: 53

DefaultValidatorConfiguration.defaultValidator() line: 43

NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method]

NativeMethodAccessorImpl.invoke(Object, Object[]) line: 62

DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 43

Method.invoke(Object, Object...) line: 498

CglibSubclassingInstantiationStrategy(SimpleInstantiationStrategy).instantiate(RootBeanDefinition, String, BeanFactory, Object, Method, Object...) line: 162

ConstructorResolver.instantiateUsingFactoryMethod(String, RootBeanDefinition, Object[]) line: 588

DefaultListableBeanFactory(AbstractAutowireCapableBeanFactory).instantiateUsingFactoryMethod(String, RootBeanDefinition, Object[]) line: 1173

显然,这个线程的调用栈是常见的spring的初始化过程。

BackgroundPreinitializer 做了什么

那么重点来看下 BackgroundPreinitializer 线程做了哪些事情:

@Order(LoggingApplicationListener.DEFAULT_ORDER + 1)

public class BackgroundPreinitializer

implements ApplicationListener<ApplicationEnvironmentPreparedEvent> {

@Override
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
    try {
        Thread thread = new Thread(new Runnable() {

            @Override
            public void run() {
                runSafely(new MessageConverterInitializer());
                runSafely(new MBeanFactoryInitializer());
                runSafely(new ValidationInitializer());
                runSafely(new JacksonInitializer());
                runSafely(new ConversionServiceInitializer());
            }

            public void runSafely(Runnable runnable) {
                try {
                    runnable.run();
                }
                catch (Throwable ex) {
                    // Ignore
                }
            }

        }, "background-preinit");
        thread.start();
    }

可以看到 BackgroundPreinitializer 类是spring boot为了加速应用的初始化,以一个独立的线程来加载hibernate validator这些组件。

这个 background-preinit 线程会吞掉所有的异常。

显然 ConfigurationImpl 初始化的异常也被吞掉了,那么如何才能获取到最原始的信息?

获取到最原始的异常信息

在 BackgroundPreinitializer 的 run() 函数里打一个断点(注意是 Suspend thread 类型, 不是 Suspend VM ),让它先不要触发 ConfigurationImpl 的加载,让spring boot的正常流程去触发 ConfigurationImpl 的加载,就可以知道具体的信息了。

那么打出来的异常信息是:

Caused by: java.lang.NoSuchMethodError: org.jboss.logging.Logger.getMessageLogger(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Object;

at org.hibernate.validator.internal.util.logging.LoggerFactory.make(LoggerFactory.java:19) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]

at org.hibernate.validator.internal.util.Version.<clinit>(Version.java:22) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]

at org.hibernate.validator.internal.engine.ConfigurationImpl.<clinit>(ConfigurationImpl.java:71) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]

at org.hibernate.validator.HibernateValidator.createGenericConfiguration(HibernateValidator.java:33) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]

at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:276) ~[validation-api-1.1.0.Final.jar:na]

at org.springframework.boot.validation.MessageInterpolatorFactory.getObject(MessageInterpolatorFactory.java:53) ~[spring-boot-1.5.3.RELEASE.jar:1.5.3.RELEASE]

那么可以看出是 org.jboss.logging.Logger 这个类不兼容,少了 getMessageLogger(Ljava/lang/Class;Ljava/lang/String;)Ljava/lang/Object 这个函数。

那么检查下应用的依赖,可以发现 org.jboss.logging.Logger 在 jboss-common-1.2.1.GA.jar 和 jboss-logging-3.3.1.Final.jar 里都有。

显然是 jboss-common-1.2.1.GA.jar 这个依赖过时了,需要排除掉。

总结异常的发生流程

应用依赖了 jboss-common-1.2.1.GA.jar ,它里面的 org.jboss.logging.Logger太老

spring boot启动时, BackgroundPreinitializer 里的线程去尝试加载 ConfigurationImpl ,然后触发了 org.jboss.logging.Logger 的函数执行问题

BackgroundPreinitializer 吃掉了异常信息,jvm把 ConfigurationImpl 标记为不可用的

spring boot正常的流程去加载 ConfigurationImpl ,jvm发现 ConfigurationImpl类是不可用,直接抛出 NoClassDefFoundError

Caused by: java.lang.NoClassDefFoundError: Could not initialize class org.hibernate.validator.internal.engine.ConfigurationImpl

深入JVM

为什么第二次尝试加载 ConfigurationImpl 时,会直接抛出 java.lang.NoClassDefFoundError: Could not initialize class ?

下面用一段简单的代码来重现这个问题:

try {

org.hibernate.validator.internal.util.Version.touch();

} catch (Throwable e) {

e.printStackTrace();

}

System.in.read();

try {

org.hibernate.validator.internal.util.Version.touch();

} catch (Throwable e) {

e.printStackTrace();

}

使用HSDB来确定类的状态

当抛出第一个异常时,尝试用HSDB来看下这个类的状态。

sudo java -classpath "$JAVA_HOME/lib/sa-jdi.jar" sun.jvm.hotspot.HSDB

然后在HSDB console里查找到 Version 的地址信息

hsdb> class org.hibernate.validator.internal.util.Version

org/hibernate/validator/internal/util/Version @0x00000007c0060218

然后在 Inspector 查找到这个地址,发现 _init_state 是5。

再看下hotspot代码,可以发现5对应的定义是 initialization_error :

// /hotspot/src/share/vm/oops/instanceKlass.hpp

// See "The Java Virtual Machine Specification" section 2.16.2-5 for a detailed description

// of the class loading & initialization procedure, and the use of the states.

enum ClassState {

allocated, // allocated (but not yet linked)

loaded, // loaded and inserted in class hierarchy (but not linked yet)

linked, // successfully linked/verified (but not initialized yet)

being_initialized, // currently running class initializer

fully_initialized, // initialized (successfull final state)

initialization_error // error happened during initialization

};

JVM规范里关于Initialization的内容

http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-5.html#jvms-5.5

从规范里可以看到初始一个类/接口有12步,比较重要的两步都用黑体标记出来了:

5: If the Class object for C is in an erroneous state, then initialization is not possible. Release LC and throw a NoClassDefFoundError.

11: Otherwise, the class or interface initialization method must have completed abruptly by throwing some exception E. If the class of E is not Error or one of its subclasses, then create a new instance of the class ExceptionInInitializerError with E as the argument, and use this object in place of E in the following step.

第一次尝试加载Version类时

当第一次尝试加载时,hotspot InterpreterRuntime在解析 invokestatic 指令时,尝试加载 org.hibernate.validator.internal.util.Version 类, InstanceKlass 的 _init_state 先是标记为 being_initialized ,然后当加载失败时,被标记为 initialization_error 。

对应 Initialization 的11步。

// hotspot/src/share/vm/oops/instanceKlass.cpp

// Step 10 and 11

Handle e(THREAD, PENDING_EXCEPTION);

CLEAR_PENDING_EXCEPTION;

// JVMTI has already reported the pending exception

// JVMTI internal flag reset is needed in order to report ExceptionInInitializerError

JvmtiExport::clear_detected_exception((JavaThread)THREAD);

{

EXCEPTION_MARK;

this_oop->set_initialization_state_and_notify(initialization_error, THREAD);

CLEAR_PENDING_EXCEPTION; // ignore any exception thrown, class initialization error is thrown below

// JVMTI has already reported the pending exception

// JVMTI internal flag reset is needed in order to report ExceptionInInitializerError

JvmtiExport::clear_detected_exception((JavaThread)THREAD);

}

DTRACE_CLASSINIT_PROBE_WAIT(error, InstanceKlass::cast(this_oop()), -1,wait);

if (e->is_a(SystemDictionary::Error_klass())) {

THROW_OOP(e());

} else {

JavaCallArguments args(e);

THROW_ARG(vmSymbols::java_lang_ExceptionInInitializerError(),

vmSymbols::throwable_void_signature(),

&args);

}

第二次尝试加载Version类时

当第二次尝试加载时,检查 InstanceKlass 的 _init_state 是 initialization_error ,则直接抛出 NoClassDefFoundError: Could not initialize class .

对应 Initialization 的5步。

// hotspot/src/share/vm/oops/instanceKlass.cpp

void InstanceKlass::initialize_impl(instanceKlassHandle this_oop, TRAPS) {

// ...

// Step 5

if (this_oop->is_in_error_state()) {

DTRACE_CLASSINIT_PROBE_WAIT(erroneous, InstanceKlass::cast(this_oop()), -1,wait);

ResourceMark rm(THREAD);

const char desc = "Could not initialize class ";

const char className = this_oop->external_name();

size_t msglen = strlen(desc) + strlen(className) + 1;

char* message = NEW_RESOURCE_ARRAY(char, msglen);

if (NULL == message) {

// Out of memory: can't create detailed error message

THROW_MSG(vmSymbols::java_lang_NoClassDefFoundError(), className);

} else {

jio_snprintf(message, msglen, "%s%s", desc, className);

THROW_MSG(vmSymbols::java_lang_NoClassDefFoundError(), message);

}

}

总结

spring boot在 BackgroundPreinitializer 类里用一个独立的线程来加载validator,并吃掉了原始异常

第一次加载失败的类,在jvm里会被标记为 initialization_error ,再次加载时会直接抛出 NoClassDefFoundError: Could not initialize class

当在代码里吞掉异常时要谨慎,否则排查问题带来很大的困难

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