Summary of Arthas vmtool command

rthas vmtool The command is mainly used to view the value of the instance memory object , For example, the following code ：

public class Instance {
    

    private static Map<String, Integer> configMap = Maps.newHashMap();
    private Map<String, Integer> configMap1 = Maps.newHashMap();


    public void init(){
    
        configMap.put("AAA", 10000);
        configMap.put("BBB", 20000);
        configMap.put("CCC", 30000);

        configMap1.put("A", 100);
        configMap1.put("B", 200);
        configMap1.put("C", 300);
    }

}

public class Test {
    

    private static Instance inst = new Instance();

    public static void main(String[] args) throws Exception{
    
        inst.init();
        Thread.sleep(600000L);
    }

}

adopt vmtool The command can view the value of a specific instance , However, this command cannot view the values of class variables , To view the value of a class variable, you need to use getstatic command , such as getstatic Class name Class variable name

Besides , It can be done by, for example vmtool --action getInstances --className org.example.Instance --express 'instances[0].get(4).getXX()’ And so on , Support ognl expression , By the way ,arthas Can traverse a list, Then find the object that is equal to a certain value inside ： Sometimes you also need to filter the collection objects according to certain conditions , Like trying to find out all age Greater than 5 Of Pojo Of name, It can be written like this
watch Test test “params[0].{? #this.age > 5}.{name}” -n 1