的Web应用程序中使用了Javassist阻塞线程

Question

可能有人帮我解释一下究竟是怎么回事，看着下面的线程转储。它是在Tomcat 7上运行的Web应用程序，我们遇到一些要求没有得到回答：

"ajp-bio-8012-exec-161" daemon prio=10 tid=0x00007fe170603000 nid=0x344f runnable [0x00007fe174fae000] 
    java.lang.Thread.State: RUNNABLE 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.io.FilePermission.init(FilePermission.java:209) 
    at java.io.FilePermission.<init>(FilePermission.java:285) 
    at java.lang.SecurityManager.checkRead(SecurityManager.java:888) 
    at java.io.File.exists(File.java:808) 
    at sun.misc.URLClassPath$FileLoader.getResource(URLClassPath.java:1080) 
    at sun.misc.URLClassPath$FileLoader.findResource(URLClassPath.java:1047) 
    at sun.misc.URLClassPath.findResource(URLClassPath.java:176) 
    at java.net.URLClassLoader$2.run(URLClassLoader.java:551) 
    at java.net.URLClassLoader$2.run(URLClassLoader.java:549) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.net.URLClassLoader.findResource(URLClassLoader.java:548) 
    at java.lang.ClassLoader.getResource(ClassLoader.java:1147) 
    at java.lang.ClassLoader.getResource(ClassLoader.java:1142) 
    at org.apache.catalina.loader.WebappClassLoader.getResource(WebappClassLoader.java:1445) 
    at java.lang.Class.getResource(Class.java:2142) 
    at javassist.ClassClassPath.find(ClassClassPath.java:84) 
    at javassist.ClassPoolTail.find(ClassPoolTail.java:317) 
    at javassist.ClassPool.find(ClassPool.java:495) 
    at javassist.ClassPool.createCtClass(ClassPool.java:479) 
    at javassist.ClassPool.get0(ClassPool.java:445) 
    - locked <0x00000000db6cdb48> (a javassist.ClassPool) 
    at javassist.ClassPool.get(ClassPool.java:414) 
    at javassist.compiler.MemberResolver.lookupClass0(MemberResolver.java:425) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:389) 
    at javassist.compiler.MemberResolver.lookupClassByJvmName(MemberResolver.java:310) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:327) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:314) 
    at javassist.compiler.Javac.compileField(Javac.java:122) 
    at javassist.compiler.Javac.compile(Javac.java:91) 
    at javassist.CtField.make(CtField.java:163) 
    at com.mycompany.validation.util.BeanGenerator.addProperty(BeanGenerator.java:157) 
    ... 
    at java.lang.Thread.run(Thread.java:745) 


"ajp-bio-8012-exec-12" daemon prio=10 tid=0x0000000000c49800 nid=0x3d99 waiting for monitor entry [0x00007fe1756b7000] 
    java.lang.Thread.State: BLOCKED (on object monitor) 
    at javassist.ClassPool.get0(ClassPool.java:432) 
    - waiting to lock <0x00000000db6cdb48> (a javassist.ClassPool) 
    at javassist.ClassPool.get(ClassPool.java:414) 
    at javassist.compiler.MemberResolver.lookupClass0(MemberResolver.java:425) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:389) 
    at javassist.compiler.MemberResolver.lookupClassByJvmName(MemberResolver.java:310) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:327) 
    at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:314) 
    at javassist.compiler.Javac.compileField(Javac.java:122) 
    at javassist.compiler.Javac.compile(Javac.java:91) 
    at javassist.CtField.make(CtField.java:163) 
    at com.mycompany.validation.util.BeanGenerator.addProperty(BeanGenerator.java:157) 
    ... 
    at java.lang.Thread.run(Thread.java:745) 



"ajp-bio-8012-exec-5" daemon prio=10 tid=0x0000000001603800 nid=0x7c77 waiting for monitor entry [0x00007fe174aaa000] 
    java.lang.Thread.State: BLOCKED (on object monitor) 
    at javassist.ClassPool.makeClass(ClassPool.java:621) 
    - waiting to lock <0x00000000db6cdb48> (a javassist.ClassPool) 
    at javassist.ClassPool.makeClass(ClassPool.java:606) 
    at com.mycompany.validation.util.BeanGenerator.init(BeanGenerator.java:334) 
    ... 
    at java.lang.Thread.run(Thread.java:745)  

我不是线程转储的专家，只是想知道如何摆脱这个问题。

具有第一螺纹锁定的对象（ClassPool），该另外两个请求线程正在等待解锁？为什么被锁定？我需要同步吗？

感谢您的任何提示！

Answer 1

您的应用程序，它具有监视器ID 0x00000000db6cdb48单ClassPool。

如果你看到ClassPool.get0的方法签名：

protected synchronized CtClass get0(String classname, boolean useCache) 

因此，它是同步的。我想你只是使用ClassPool.getDefault（）。你必须知道这个方法返回一个实例，所以你的所有调用都会被同步。

为每个线程创建一个新池（例如new ClassPool(ClassPool.getDefault())）并且它会很好。

除此之外，你可能会检查你的secrurity经理，为什么需要这么长。