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使用JDK工具jmap和jhat监控Java进程 javaJdkSAPSAP云平台SAP Cloud Platform 

程序员文章站 2022-03-25 17:58:44
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Suppose you have a running Java process and you would like to inspect its running status, for example how many object instance are created or memory consumption status, you can use some standard tool provided by JDK.

This blog is written based on JDK 1.8. The sample code I am using to simulate a endless running process:

package jmap;

class Tool{
    private int count = 0;
    public void Run() throws InterruptedException{
        while(true){
            System.out.println("Hello: " + this.count++);
            Thread.sleep(5000);
        }
    }
}
public class JMapTest {

    public static void main(String[] args) throws InterruptedException {
        Tool tool = new Tool();
        tool.Run();
    }
}

(1) First get process id found in task manager: 15392

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

(2) use command line jmap -dump:format=b,file=c:\temp\heapstatus.bin 15392 jmap is a standard tool provided by JDK in this folder in my laptop:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

heap bin file is generated now:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

(3) Use another tool jhat to parse the bin file: jhat c:\temp\heapstatus.bin

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

Then access localhost:7000 in browser:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

Click hyperlink class jmap.Tool, now I can find out that the instance of my tool class @0x7166babd8 has member attribute count with value 49.

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

(4) There is a plugin in Eclipse MAT – Memory Analyzer Tool which can achieve the same.

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

Once plugin is installed, you can make them visible in “Show View”:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

Drag your bin file into the view and the heap file will be parsed automatically. Click “Find object by address”:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

Type address of object instance you want to inspect:

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

You can get the same result as you get previously in localhost:7000

 

使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform 

 

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使用JDK工具jmap和jhat监控Java进程
            
    
    
        javaJdkSAPSAP云平台SAP Cloud Platform