Arthas - 查找类

问题

当更新了类之后,怎么样在生产环境判断类或对象中的字段,方法有没有被正常更新呢?这个时候可以使用Arthas的sc命令来查找JVM中已经加载的类

操作

• sc -d com.ct.hear.entity.*
  通过这个命令可知,实体类加载了两个对象,Article和MessageLog

[arthas@4967]$ sc -d com.ct.hear.entity.* class-info com.ct.hear.entity.Article code-source file:/data/1data/1data-project-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/ name com.ct.hear.entity.Article isInterface false isAnnotation false isEnum false isAnonymousClass false isArray false isLocalClass false isMemberClass false isPrimitive false isSynthetic false simple-name Article modifier public annotation io.swagger.annotations.ApiModel interfaces java.io.Serializable super-class +-java.lang.Object class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@21b8d17c +-sun.misc.Launcher$AppClassLoader@70dea4e +-sun.misc.Launcher$ExtClassLoader@2038ae61 classLoaderHash 21b8d17c class-info com.ct.hear.entity.MessageLog code-source file:/data/1data/1data-project-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/ name com.ct.hear.entity.MessageLog isInterface false isAnnotation false isEnum false isAnonymousClass false isArray false isLocalClass false isMemberClass false isPrimitive false isSynthetic false simple-name MessageLog modifier public annotation io.swagger.annotations.ApiModel interfaces java.io.Serializable super-class +-java.lang.Object class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@21b8d17c +-sun.misc.Launcher$AppClassLoader@70dea4e +-sun.misc.Launcher$ExtClassLoader@2038ae61 classLoaderHash 21b8d17c Affect(row-cnt:2) cost in 17 ms. 

• sc -d *UserController | grep class
  sc命令还支持管道,使用这个命令来获取UserController的信息

[arthas@81]$ sc -d *UserController | grep class class-info com.example.demo.arthas.user.UserController code-source file:/root/demo-arthas-spring-boot.jar!/BOOT-INF/classes!/ super-class +-java.lang.Object class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@728938a9 classLoaderHash 728938a9 

• sc -d -f com.ct.hear.entity.*
  再使用这个命令获取到该Object下的Field

[arthas@4967]$ sc -d -f com.ct.hear.entity.Article class-info com.ct.hear.entity.Article code-source file:/data/1data/1data-project-0.0.1-SNAPSHOT.jar!/BOOT-INF/classes!/ name com.ct.hear.entity.Article isInterface false isAnnotation false isEnum false isAnonymousClass false isArray false isLocalClass false isMemberClass false isPrimitive false isSynthetic false simple-name Article modifier public annotation io.swagger.annotations.ApiModel interfaces java.io.Serializable super-class +-java.lang.Object class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@21b8d17c +-sun.misc.Launcher$AppClassLoader@70dea4e +-sun.misc.Launcher$ExtClassLoader@2038ae61 classLoaderHash 21b8d17c fields name serialVersionUID type long modifier final,private,static value 1 name id type java.lang.String modifier private annotation com.baomidou.mybatisplus.annotation.TableId,io.swagger.annotations.ApiModelProperty name title type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name summary type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name pcontent type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name emotion type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name pubTime type java.lang.Long modifier private annotation io.swagger.annotations.ApiModelProperty name createTime type java.lang.Long modifier private annotation io.swagger.annotations.ApiModelProperty name url type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name author type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name authorAddress type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name authorGender type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name mediaName type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name mediaType type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name mediaArea type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name coreWords type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name monitorWords type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name fromSource type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name readNum type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name commentNum type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name praiseNum type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name forwardNum type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name column type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty,com.baomidou.mybatisplus.annotation.TableField name topic type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name fansNum type java.lang.Integer modifier private annotation io.swagger.annotations.ApiModelProperty name verifyType type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty name parentId type java.lang.String modifier private annotation io.swagger.annotations.ApiModelProperty Affect(row-cnt:1) cost in 18 ms. 

思考

如果一个类被多个类加载器(classLoader)加载,调用第一条命令会出现多个对象,这是因为对于JVM来说,不同的类加载器加载出的对象是肯定不同的;两个对象equals的前提,就是它们由相同的类加载器加载,可以移步到JVM篇章看详细解答