$$和<生成>是什么在java stacktrace中意味着什么？ [英] What does $$ and <generated> means in java stacktrace?

问题描述

很多时候我得到像这样的堆栈跟踪（请参阅箭头中的混淆行）：

Many times I get stacktraces like this one (please see the arrow for the confusing line):

org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]; constraint [PRIMARY]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement
                at org.springframework.orm.hibernate5.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:164)
                at org.springframework.orm.hibernate5.HibernateTransactionManager.convertHibernateAccessException(HibernateTransactionManager.java:741)
                at org.springframework.orm.hibernate5.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:589)
                at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761)
                at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
                at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:485)
                at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:291)
                at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
                at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
                at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653)
--------->      at com.panpwr.admin.services.detector.SimpleDetectorPersistenceService$$EnhancerBySpringCGLIB$$66303639.saveComplexRuleAndActionTemplates(<generated>)
                at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
                at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
                at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
...
...
...

$$符号是什么，生成是什么意思？
com.panpwr.admin.services.detector.SimpleDetectorPersistenceService $$ EnhancerBySpringCGLIB $$ 66303639.saveComplexRuleAndActionTemplates（< generated>）

What Does the $$ sign, and what is the 'generated' means in this line? com.panpwr.admin.services.detector.SimpleDetectorPersistenceService$$EnhancerBySpringCGLIB$$66303639.saveComplexRuleAndActionTemplates(<generated>)

为什么它只说执行的方法而不是它中的行？

And why it only says the executed method but not the line in it?

推荐答案

$ 是类名中允许的字符。

$ is an allowed character in class names.

名称 SimpleDetectorPersistenceService $$ EnhancerBySpringCGLIB $$ 66303639 提示它是一个由Spring在运行时动态生成的类使用CGLIB的框架。

The name SimpleDetectorPersistenceService$$EnhancerBySpringCGLIB$$66303639 hints that it is a class which was dynamically generated at runtime by Spring framework using CGLIB.

他们使用 $$ 和一个数字偏移量来使这个类名唯一，以避免与现有的类。

They use $$ and a numeric offset to make this class name unique to avoid conflicts with existing classes.

stracktrace中的字符串（< generated>）也是由 CGLIB ：

当CGLIB在运行时创建一个类时，它使用< generated> ; 作为源文件名称的占位符。然后，堆栈跟踪只是打印此字符串而不是真实的源文件和行号。

The string (<generated>) in the stracktrace too was generated by CGLIB:
When CGLIB creates a class at runtime it uses <generated> as placeholder for the name of the source file. The stacktrace then simply prints this string instead of the real source file and line number.

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