mirror of https://github.com/alibaba/arthas.git
You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
161 lines
6.3 KiB
Markdown
161 lines
6.3 KiB
Markdown
# classloader
|
|
|
|
[`classloader` online tutorial](https://arthas.aliyun.com/doc/arthas-tutorials?language=en&id=command-classloader)
|
|
|
|
::: tip
|
|
View hierarchy, urls and classes-loading info for the class-loaders.
|
|
:::
|
|
|
|
`classloader` can search and print out the URLs for a specified resource from one particular classloader. It is quite handy when analyzing `ResourceNotFoundException`.
|
|
|
|
## Options
|
|
|
|
| Name | Specification |
|
|
| --------------------: | :----------------------------------------------------------------------------------------------------------- |
|
|
| [l] | list all classloader instances |
|
|
| [t] | print classloader's hierarchy |
|
|
| [a] | list all the classes loaded by all the classloaders (use it with great caution since the output can be huge) |
|
|
| [c:] | print classloader's hashcode |
|
|
| `[classLoaderClass:]` | The class name of the ClassLoader that executes the expression. |
|
|
| `[c: r:]` | using ClassLoader to search resource |
|
|
| `[c: load:]` | using ClassLoader to load class |
|
|
|
|
## Usage
|
|
|
|
### View statistics categorized by class type
|
|
|
|
```bash
|
|
$ classloader
|
|
name numberOfInstances loadedCountTotal
|
|
com.taobao.arthas.agent.ArthasClassloader 1 2115
|
|
BootstrapClassLoader 1 1861
|
|
sun.reflect.DelegatingClassLoader 5 5
|
|
sun.misc.Launcher$AppClassLoader 1 4
|
|
sun.misc.Launcher$ExtClassLoader 1 1
|
|
Affect(row-cnt:5) cost in 3 ms.
|
|
```
|
|
|
|
### View statistics categorized by loaded classes number
|
|
|
|
```bash
|
|
$ classloader -l
|
|
name loadedCount hash parent
|
|
BootstrapClassLoader 1861 null null
|
|
com.taobao.arthas.agent.ArthasClassloader@68b31f0a 2115 68b31f0a sun.misc.Launcher$ExtClassLoader@66350f69
|
|
sun.misc.Launcher$AppClassLoader@3d4eac69 4 3d4eac69 sun.misc.Launcher$ExtClassLoader@66350f69
|
|
sun.misc.Launcher$ExtClassLoader@66350f69 1 66350f69 null
|
|
Affect(row-cnt:4) cost in 2 ms.
|
|
```
|
|
|
|
### View class-loaders hierarchy
|
|
|
|
```bash
|
|
$ classloader -t
|
|
+-BootstrapClassLoader
|
|
+-sun.misc.Launcher$ExtClassLoader@66350f69
|
|
+-com.taobao.arthas.agent.ArthasClassloader@68b31f0a
|
|
+-sun.misc.Launcher$AppClassLoader@3d4eac69
|
|
Affect(row-cnt:4) cost in 3 ms.
|
|
```
|
|
|
|
### Show the URLs of the URLClassLoader
|
|
|
|
```bash
|
|
$ classloader -c 3d4eac69
|
|
file:/private/tmp/math-game.jar
|
|
file:/Users/hengyunabc/.arthas/lib/3.0.5/arthas/arthas-agent.jar
|
|
|
|
Affect(row-cnt:9) cost in 3 ms.
|
|
```
|
|
|
|
Note that the hashcode changes, you need to check the current ClassLoader information first, and extract the hashcode corresponding to the ClassLoader.
|
|
|
|
For ClassLoader with only unique instance, it can be specified by class name, which is more convenient to use:
|
|
|
|
```bash
|
|
$ classloader --classLoaderClass sun.misc.Launcher$AppClassLoader
|
|
file:/private/tmp/math-game.jar
|
|
file:/Users/hengyunabc/.arthas/lib/3.0.5/arthas/arthas-agent.jar
|
|
|
|
Affect(row-cnt:9) cost in 3 ms.
|
|
```
|
|
|
|
### Use the classloader to load resource
|
|
|
|
```bash
|
|
$ classloader -c 3d4eac69 -r META-INF/MANIFEST.MF
|
|
jar:file:/System/Library/Java/Extensions/MRJToolkit.jar!/META-INF/MANIFEST.MF
|
|
jar:file:/private/tmp/math-game.jar!/META-INF/MANIFEST.MF
|
|
jar:file:/Users/hengyunabc/.arthas/lib/3.0.5/arthas/arthas-agent.jar!/META-INF/MANIFEST.MF
|
|
```
|
|
|
|
Use the classloader to load `.class` resource
|
|
|
|
```shell
|
|
$ classloader -c 1b6d3586 -r java/lang/String.class
|
|
jar:file:/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk/Contents/Home/jre/lib/rt.jar!/java/lang/String.class
|
|
```
|
|
|
|
### Use the classloader to load class
|
|
|
|
```bash
|
|
$ classloader -c 3d4eac69 --load demo.MathGame
|
|
load class success.
|
|
class-info demo.MathGame
|
|
code-source /private/tmp/math-game.jar
|
|
name demo.MathGame
|
|
isInterface false
|
|
isAnnotation false
|
|
isEnum false
|
|
isAnonymousClass false
|
|
isArray false
|
|
isLocalClass false
|
|
isMemberClass false
|
|
isPrimitive false
|
|
isSynthetic false
|
|
simple-name MathGame
|
|
modifier public
|
|
annotation
|
|
interfaces
|
|
super-class +-java.lang.Object
|
|
class-loader +-sun.misc.Launcher$AppClassLoader@3d4eac69
|
|
+-sun.misc.Launcher$ExtClassLoader@66350f69
|
|
classLoaderHash 3d4eac69
|
|
```
|
|
|
|
### Statistics ClassLoader actually used URLs and unused URLs
|
|
|
|
::: warning
|
|
Note that statistics are based on all classes currently loaded by the JVM. Does not mean that `Unused URLs` can be removed from the application. Because it may be necessary to load classes from `Unused URLs` in the future, or to load `resources`.
|
|
:::
|
|
|
|
```
|
|
$ classloader --url-stat
|
|
com.taobao.arthas.agent.ArthasClassloader@3c41660, hash:3c41660
|
|
Used URLs:
|
|
file:/Users/admin/.arthas/lib/3.5.6/arthas/arthas-core.jar
|
|
Unused URLs:
|
|
|
|
sun.misc.Launcher$AppClassLoader@75b84c92, hash:75b84c92
|
|
Used URLs:
|
|
file:/Users/admin/code/java/arthas/math-game/target/math-game.jar
|
|
file:/Users/admin/.arthas/lib/3.5.6/arthas/arthas-agent.jar
|
|
Unused URLs:
|
|
|
|
sun.misc.Launcher$ExtClassLoader@7f31245a, hash:7f31245a
|
|
Used URLs:
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/sunec.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/sunjce_provider.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/localedata.jar
|
|
Unused URLs:
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/nashorn.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/cldrdata.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/legacy8ujsse.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/jfxrt.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/dnsns.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/openjsse.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/sunpkcs11.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/jaccess.jar
|
|
file:/tmp/jdk1.8/Contents/Home/jre/lib/ext/zipfs.jar
|
|
```
|