mirror of
https://gitee.com/arthas/arthas.git
synced 2024-12-05 05:37:37 +08:00
155 lines
5.9 KiB
Markdown
155 lines
5.9 KiB
Markdown
|
||
|
||
下面介绍`classloader`命令的功能。
|
||
|
||
先访问一个jsp网页，触发jsp的加载： https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/hello
|
||
|
||
### 列出所有ClassLoader
|
||
|
||
`classloader -l`{{execute T2}}
|
||
|
||
```bash
|
||
$ classloader -l
|
||
name loadedCount hash parent
|
||
BootstrapClassLoader 2724 null null
|
||
com.taobao.arthas.agent.ArthasClassloader@411ce1ab 2009 411ce1ab sun.misc.Launcher$ExtClassLoader@7494e528
|
||
com.taobao.arthas.agent.ArthasClassloader@22ae1234 1253 22ae1234 sun.misc.Launcher$ExtClassLoader@7494e528
|
||
org.apache.jasper.servlet.JasperLoader@65361d9a 1 65361d9a TomcatEmbeddedWebappClassLoader
|
||
context: ROOT
|
||
delegate: true
|
||
----------> Parent Classloader:
|
||
org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
|
||
|
||
TomcatEmbeddedWebappClassLoader 0 8546cd5 org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
|
||
context: ROOT
|
||
delegate: true
|
||
----------> Parent Classloader:
|
||
org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
|
||
|
||
org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3 5416 1be6f5c3 sun.misc.Launcher$AppClassLoader@3d4eac69
|
||
sun.misc.Launcher$AppClassLoader@3d4eac69 45 3d4eac69 sun.misc.Launcher$ExtClassLoader@7494e528
|
||
sun.misc.Launcher$ExtClassLoader@7494e528 4 7494e528 null
|
||
```
|
||
|
||
* TomcatEmbeddedWebappClassLoader 加载的class数量是0，所以在spring boot embedded tomcat里，它只是一个空壳，所有的类加载都是`LaunchedURLClassLoader`完成的
|
||
|
||
请记下你的classLoaderHash，后面需要使用它。在这里，它是 `65361d9a`。
|
||
|
||
注意：请使用你的classLoaderHash值覆盖 `<classLoaderHash>` ，然后手动执行下面所有所述命令：
|
||
|
||
### 列出ClassLoader里加载的所有类
|
||
|
||
列出上面的`org.apache.jasper.servlet.JasperLoader`加载的类：
|
||
|
||
`classloader -a -c <classLoaderHash>`
|
||
|
||
```bash
|
||
$ classloader -a -c 65361d9a
|
||
hash:1698045338, org.apache.jasper.servlet.JasperLoader@65361d9a
|
||
org.apache.jsp.jsp.hello_jsp
|
||
```
|
||
|
||
### 查看类的classloader层次
|
||
|
||
`sc -d org.apache.jsp.jsp.hello_jsp`{{execute T2}}
|
||
|
||
### 查看ClassLoader树
|
||
|
||
|
||
`classloader -t`{{execute T2}}
|
||
|
||
```
|
||
$ classloader -t
|
||
+-BootstrapClassLoader
|
||
+-sun.misc.Launcher$ExtClassLoader@28cbbddd
|
||
+-com.taobao.arthas.agent.ArthasClassloader@8c25e55
|
||
+-sun.misc.Launcher$AppClassLoader@55f96302
|
||
+-org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
|
||
+-TomcatEmbeddedWebappClassLoader
|
||
context: ROOT
|
||
delegate: true
|
||
----------> Parent Classloader:
|
||
org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
|
||
|
||
+-org.apache.jasper.servlet.JasperLoader@21ae0fe2
|
||
```
|
||
|
||
### 查看URLClassLoader实际的urls
|
||
|
||
比如上面查看到的spring LaunchedURLClassLoader的 hashcode是`1be6f5c3`，可以通过`-c`参数来指定classloader，从而查看URLClassLoader实际的urls：
|
||
|
||
`classloader -c <classLoaderHash>`
|
||
|
||
```
|
||
$ classloader -c 1be6f5c3
|
||
jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/classes!/
|
||
jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/lib/spring-boot-starter-aop-1.5
|
||
.13.RELEASE.jar!/
|
||
...
|
||
```
|
||
|
||
### 加载指定ClassLoader里的资源文件
|
||
|
||
查找指定的资源文件： `classloader -c <classLoaderHash> -r logback-spring.xml`
|
||
|
||
```
|
||
$ classloader -c 1be6f5c3 -r logback-spring.xml
|
||
jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/classes!/logback-spring.xml
|
||
```
|
||
也可以尝试查找类的class文件：
|
||
|
||
`classloader -c <classLoaderHash> -r java/lang/String.class`
|
||
|
||
```bash
|
||
$ 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
|
||
```
|
||
|
||
### 尝试加载指定的类
|
||
|
||
比如用上面的spring LaunchedURLClassLoader 尝试加载 `ch.qos.logback.classic.spi.StackTraceElementProxy` ：
|
||
|
||
首先使用`sc ch.qos.logback.classic.spi.StackTraceElementProxy`{{execute T2}}查看，可发现未加载：
|
||
|
||
```bash
|
||
Affect(row-cnt:0) cost in 18 ms.
|
||
```
|
||
|
||
因而使用spring LaunchedURLClassLoader 尝试加载：
|
||
|
||
`classloader -c <classLoaderHash> --load ch.qos.logback.classic.spi.StackTraceElementProxy`
|
||
|
||
```bash
|
||
$ classloader -c 1be6f5c3 --load ch.qos.logback.classic.spi.StackTraceElementProxy
|
||
load class success.
|
||
class-info ch.qos.logback.classic.spi.StackTraceElementProxy
|
||
code-source file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/lib/logback-classic-1.
|
||
1.11.jar!/
|
||
name ch.qos.logback.classic.spi.StackTraceElementProxy
|
||
isInterface false
|
||
isAnnotation false
|
||
isEnum false
|
||
isAnonymousClass false
|
||
isArray false
|
||
isLocalClass false
|
||
isMemberClass false
|
||
isPrimitive false
|
||
isSynthetic false
|
||
simple-name StackTraceElementProxy
|
||
modifier public
|
||
annotation
|
||
interfaces java.io.Serializable
|
||
super-class +-java.lang.Object
|
||
class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@5674cd4d
|
||
+-sun.misc.Launcher$AppClassLoader@70dea4e
|
||
+-sun.misc.Launcher$ExtClassLoader@56a96482
|
||
classLoaderHash 5674cd4d
|
||
```
|
||
|
||
再次使用`sc ch.qos.logback.classic.spi.StackTraceElementProxy`{{execute T2}}查看，发现已经加载：
|
||
|
||
```bash
|
||
ch.qos.logback.classic.spi.StackTraceElementProxy
|
||
Affect(row-cnt:1) cost in 19 ms.
|
||
```
|