DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports
Events Video Library
Refcards
Trend Reports

Events

View Events Video Library

Zones

Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks

How does AI transform chaos engineering from an experiment into a critical capability? Learn how to effectively operationalize the chaos.

Data quality isn't just a technical issue: It impacts an organization's compliance, operational efficiency, and customer satisfaction.

Are you a front-end or full-stack developer frustrated by front-end distractions? Learn to move forward with tooling and clear boundaries.

Developer Experience: Demand to support engineering teams has risen, and there is a shift from traditional DevOps to workflow improvements.

Related

  • Jakarta WebSocket Essentials: A Guide to Full-Duplex Communication in Java
  • Java Is Greener on Arm
  • Mastering Date/Time APIs: Challenges With Java's Calendar and JDK Date/Time APIs
  • Java 23: What Developers Need to Know

Trending

  • Integrating Apache Spark With Drools: A Loan Approval Demo
  • Securing DevOps Pipelines: A Practical Guide to Balancing Speed and Security
  • Enterprise Data Loss Prevention (DLP) Security Policies and Tuning
  • Security by Design: Building Full-Stack Applications With DevSecOps
  1. DZone
  2. Coding
  3. Java
  4. JDK 9: An Introduction to StackWalker

JDK 9: An Introduction to StackWalker

StackWalker is an API for stack walking that allows easy filtering of, and lazy access to, the information in stack traces.

By 
Hemambara Vamsi Kotari user avatar
Hemambara Vamsi Kotari
·
Dec. 22, 16 · Tutorial
Likes (24)
Comment
Save
Tweet
Share
24.3K Views

Join the DZone community and get the full member experience.

Join For Free

StackWalker has been introduced in JDK9 as JEP-259. The concepts in this article are taken from JEP-259. 

StackWalker gives the snapshot of the stack trace of the current thread at any given point of time and has methods to walk over it. Benefits of using StackWalker over Thread::getStackTrace() (prior to JDK9), which are missing in prior releases, are:

  • Filter / assert / skip certain classes.

  • Get the instance of declaring the class itself.

  • Get either short stack trace or complete stack trace, instead of pulling the complete stack trace itself.

The complete code snippet has been put at the end of the article. Let's walk through each section:

Get All Stack Trace Information

Print all stack frame info.

stackFrame.getDeclaringClass()
  // Will give instance of declaring class
List<StackFrame> stack =
  StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) -> s.collect(Collectors.toList()));
System.out.println("All frames : \n" + stack.toString());
//output: 

All frames :
[StackWalkerExample$StackWalker4.stackWalk4(StackWalkerExample.java:46), 
 StackWalkerExample$StackWalker3.stackWalk3(StackWalkerExample.java:39), 
 StackWalkerExample$StackWalker2.stackWalk2(StackWalkerExample.java:33), 
 StackWalkerExample$StackWalker1.stackWalk1(StackWalkerExample.java:27), 
 StackWalkerExample.stackWalk(StackWalkerExample.java:13), 
 StackWalkerExample.main(StackWalkerExample.java:22)]


Filter for Certain Classes

// Filter for interesting classes
final List<Class> interestingClasses = new ArrayList<>();
interestingClasses.add(StackWalker3.class);
Optional<StackFrame> framesWithInterestingClass = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) ->
s.filter(f -> interestingClasses.contains(f.getDeclaringClass())).findFirst()
);

System.out.println("Frame with interseting class : \n"+framesWithInterestingClass.toString());
//output:
rame with interseting class :
Optional[StackWalkerExample$StackWalker3.stackWalk3(StackWalkerExample.java:39)]


Skip Classes in the Stack Frame

Trim the stack frame by skipping a few classes. Using this, we can consider short stack frames:

// Frames with skip
List<StackFrame> framesAfterSkip = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) ->
s.skip(2).collect(Collectors.toList()));

System.out.println("Frames after skip : \n"+framesAfterSkip.toString());


//Output:

Frames after skip :
[StackWalkerExample$StackWalker2.stackWalk2(StackWalkerExample.java:33), 
 StackWalkerExample$StackWalker1.stackWalk1(StackWalkerExample.java:27), 
 StackWalkerExample.stackWalk(StackWalkerExample.java:13), 
 StackWalkerExample.main(StackWalkerExample.java:22)]

// It does not have StackWalker3& StackWalker4, the first two in the list


Complete Code

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import java.lang.StackWalker.*;

/**
 * Created by vkotari on 12/18/2016.
 */
public class StackWalkerExample {

  private class StackWalker4{
        public void stackWalk4(){
            List<StackFrame> stack =
                    StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) -> s.collect(Collectors.toList()));
            System.out.println("All frames : \n" + stack.toString());

            for(StackFrame stackFrame : stack){
                System.out.println(stackFrame.getDeclaringClass().toString());
            }

            // Filter for interesting classes
            final List<Class> interestingClasses = new ArrayList<>();
            interestingClasses.add(StackWalker3.class);
            Optional<StackFrame> framesWithInterestingClass = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) ->

                s.filter(f -> interestingClasses.contains(f.getDeclaringClass())).findFirst()
            );

            System.out.println("Frame with interseting class : \n"+framesWithInterestingClass.toString());

            // Frames with skip
            List<StackFrame> framesAfterSkip = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).walk((s) ->
                    s.skip(2).collect(Collectors.toList())
            );

            System.out.println("Frames after skip : \n"+framesAfterSkip.toString());


        }
    }
    public void stackWalk(){
        new StackWalker1().stackWalk1();
    }

    public void print(){
        System.out.println("Hello World.");
    }

    public static void main(String args[]){
        System.out.println("StackWalkerExample...");
        new StackWalkerExample().stackWalk();
    }

    private class StackWalker1{
        public void stackWalk1(){
            new StackWalker2().stackWalk2();
        }
    }

    private class StackWalker2{
        public void stackWalk2(){
            new StackWalker3().stackWalk3();
        }
    }

    private class StackWalker3{
        public void stackWalk3(){
            new StackWalker4().stackWalk4();
        }
    }
}


Java Development Kit Java (programming language)

Opinions expressed by DZone contributors are their own.

Related

  • Jakarta WebSocket Essentials: A Guide to Full-Duplex Communication in Java
  • Java Is Greener on Arm
  • Mastering Date/Time APIs: Challenges With Java's Calendar and JDK Date/Time APIs
  • Java 23: What Developers Need to Know

Partner Resources

×

Comments

The likes didn't load as expected. Please refresh the page and try again.

ABOUT US

  • About DZone
  • Support and feedback
  • Community research
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Core Program
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 3343 Perimeter Hill Drive
  • Suite 100
  • Nashville, TN 37211
  • [email protected]

Let's be friends: