classloader

查看classloader的继承树，urls，类加载信息

classloader 命令将 JVM 中所有的classloader的信息统计出来，并可以展示继承树，urls等。

可以让指定的classloader去getResources，打印出所有查找到的resources的url。对于ResourceNotFoundException比较有用。

参数说明

参数名称 参数说明
[l] 按类加载实例进行统计
[t] 打印所有ClassLoader的继承树
[a] 列出所有ClassLoader加载的类，请谨慎使用
[c:] ClassLoader的hashcode
[c: r:] 用ClassLoader去查找resource

使用参考

  • 按类加载类型查看统计信息
  1. $ classloader
  2.  name                                                   numberOfInstances  loadedCountTotal
  3.  com.taobao.pandora.service.loader.ModuleClassLoader    29                 11659
  4.  com.taobao.pandora.boot.loader.ReLaunchURLClassLoader  1                  5308
  5.  BootstrapClassLoader                                   1                  3711
  6.  com.taobao.arthas.agent.ArthasClassloader              2                  2825
  7.  sun.reflect.DelegatingClassLoader                      332                332
  8.  java.net.URLClassLoader                                1                  285
  9.  sun.misc.Launcher$AppClassLoader                       1                  77
  10.  sun.misc.Launcher$ExtClassLoader                       1                  46
  11.  com.alibaba.fastjson.util.ASMClassLoader               2                  3
  12.  org.jvnet.hk2.internal.DelegatingClassLoader           2                  2
  13.  sun.reflect.misc.MethodUtil                            1                  1
  14. Affect(row-cnt:11) cost in 66 ms.
  • 按类加载实例查看统计信息
  1. $ classloader -l
  2.  name                                                            loadedCount  hash      parent
  3.  BootstrapClassLoader                                            3711         null      null
  4.  com.alibaba.fastjson.util.ASMClassLoader@3bbaa1b8               2            3bbaa1b8  monitor's ModuleClassLoader
  5.  com.alibaba.fastjson.util.ASMClassLoader@5e255d0b               1            5e255d0b  eagleeye-core's ModuleClassLoader
  6.  com.taobao.arthas.agent.ArthasClassloader@4fa2d7e6              1795         4fa2d7e6  sun.misc.Launcher$ExtClassLoader@a38d7a3
  7.  com.taobao.arthas.agent.ArthasClassloader@522400c2              1033         522400c2  sun.misc.Launcher$ExtClassLoader@a38d7a3
  8.  com.taobao.pandora.boot.loader.ReLaunchURLClassLoader@1817d444  5308         1817d444  sun.misc.Launcher$AppClassLoader@14dad5dc
  9.  tbsession's ModuleClassLoader                                   285          609cd4d8  null
  10.  pandora-qos-service's ModuleClassLoader                         267          2f8dad04  null
  11.  pandora-framework's ModuleClassLoader                           78           4009e306  null
  12.  filesync-client's ModuleClassLoader                             4            4b8ee4de  null
  13.  rocketmq-client's ModuleClassLoader                             431          247bddad  null
  14.  eagleeye-core's ModuleClassLoader                               451          1ba9117e  null
  15.  alimonitor-jmonitor's ModuleClassLoader                         134          22fcf7ab  null
  16.  metaq-client's ModuleClassLoader                                35           41a2befb  null
  17.  hsf-mock's ModuleClassLoader                                    3            2002fc1d  null
  18.  monitor's ModuleClassLoader                                     1427         131ef10   null
  19.  spas-sdk-service's ModuleClassLoader                            7            10d307f1  null
  20.  vipserver-client's ModuleClassLoader                            137          7a419da4  null
  21.  metrics's ModuleClassLoader                                     146          696da30b  null
  22.  mtop-uncenter's ModuleClassLoader                               922          79d8407f  null
  23.  spas-sdk-client's ModuleClassLoader                             235          4944252c  null
  24.  live-profiler-pandora's ModuleClassLoader                       1            6913c1fb  null
  25.  notify-tr-client's ModuleClassLoader                            472          fba92d3   null
  26.  ons-sdk's ModuleClassLoader                                     70           23348b5d  null
  27.  tair-plugin's ModuleClassLoader                                 1053         7c9d8e2   null
  28.  tddl-client's ModuleClassLoader                                 2354         4988d8b8  null
  29.  config-client's ModuleClassLoader                               93           429bffaa  null
  30.  diamond-client's ModuleClassLoader                              360          3d5c822d  null
  31.  pandolet's ModuleClassLoader                                    99           41e1e210  null
  32.  hsf's ModuleClassLoader                                         1796         3232a28a  null
  33.  acl.plugin's ModuleClassLoader                                  379          67080771  null
  34.  buc.sso.client.plugin's ModuleClassLoader                       195          13b6aecc  null
  35.  unitrouter's ModuleClassLoader                                  64           7e5afaa6  null
  36.  switch's ModuleClassLoader                                      104          24313fcc  null
  37.  hsf-notify-client's ModuleClassLoader                           57           4d0f2471  null
  38.  java.net.URLClassLoader@7ec7ffd3                                285          7ec7ffd3  sun.misc.Launcher$ExtClassLoader@a38d7a3
  39.  javax.management.remote.rmi.NoCallStackClassLoader@53f65459     1            53f65459  null
  40.  javax.management.remote.rmi.NoCallStackClassLoader@2833cc44     1            2833cc44  null
  41.  org.jvnet.hk2.internal.DelegatingClassLoader@72cda8ee           1            72cda8ee  monitor's ModuleClassLoader
  42.  org.jvnet.hk2.internal.DelegatingClassLoader@1f57f96d           1            1f57f96d  monitor's ModuleClassLoader
  43.  sun.misc.Launcher$AppClassLoader@14dad5dc                       77           14dad5dc  sun.misc.Launcher$ExtClassLoader@a38d7a3
  44.  sun.misc.Launcher$ExtClassLoader@a38d7a3                        46           a38d7a3   null
  45.  sun.reflect.misc.MethodUtil@1201f221                            1            1201f221  sun.misc.Launcher$AppClassLoader@14dad5dc
  • 查看ClassLoader的继承树
  1. $ classloader -t
  2. +-BootstrapClassLoader
  3. +-unitrouter's ModuleClassLoader
  4. +-diamond-client's ModuleClassLoader
  5. +-sun.misc.Launcher$ExtClassLoader@548a102f
  6. | +-sun.misc.Launcher$AppClassLoader@14dad5dc
  7. |   +-com.taobao.arthas.agent.AgentLauncher$1@334e6bb8
  8. |   | +-sun.reflect.DelegatingClassLoader@328b3a05
  9. |   | +-sun.reflect.DelegatingClassLoader@73f44f24
  • 查看URLClassLoader实际的urls
  1. $ classloader -c 5ffe9775
  2. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/commons-lang-2.6.jar
  3. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/log4j-1.2.16.jar
  4. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/logger.api-0.1.4.jar
  5. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/pandora.api-2.0.7-SNAPSHOT.jar
  6. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/pandora.container-2.0.7-SNAPSHOT.jar
  7. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/pandora.thirdcontainer-2.0.7-SNAPSHOT.jar
  8. file:/Users/hello/soft/taobao-tomcat-7.0.64/deploy/taobao-hsf.sar/lib/picocontainer-2.14.3.jar
  • 使用ClassLoader去查找resource
  1. $ classloader -c 226b143b -r META-INF/MANIFEST.MF
  2.  jar:file:/Users/hello/.m2/repository/javax/enterprise/cdi-api/1.0/cdi-api-1.0.jar!/META-INF/MANIFEST.MF
  3.  jar:file:/Users/hello/.m2/repository/javax/annotation/jsr250-api/1.0/jsr250-api-1.0.jar!/META-INF/MANIFEST.MF

也可以尝试查找类的class文件：

  1. $ classloader -c 1b6d3586 -r java/lang/String.class
  2.  jar:file:/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk/Contents/Home/jre/lib/rt.jar!/java/lang/String.class

原文: https://alibaba.github.io/arthas/classloader.html