AppMap for Java

About

appmap-java is a Java agent for recording AppMaps of your code. “AppMap” is a data format which records code structure (modules, classes, and methods), code execution events (function calls and returns), and code metadata (repo name, repo URL, commit SHA, labels, etc). It’s more granular than a performance profile, but it’s less granular than a full debug trace. It’s designed to be optimal for understanding the design intent and structure of code and key data flows.

There are several ways to record AppMaps of your Java program using the appmap agent:

  • Run your tests (JUnit, TestNG) with the Java agent. An AppMap will be generated for each test.
  • Run your application server with AppMap remote recording enabled, and use the AppMap browser extension to start, stop, and upload recordings.
  • Record the code with AppMap.record API, which returns JSON containing the code execution trace.

Once you have made a recording, there are two ways to view automatically generated diagrams of the AppMaps.

The first option is to load the diagrams directly in your IDE, using the AppMap for IntelliJ IDEA or AppMap for Visual Studio Code.

The second option is to upload them to the AppMap Cloud using the AppMap Cloud CLI.

Supported versions

  • JDK 8+
  • JUnit, TestNG

Configuration

When you run your program, the agent reads configuration settings from appmap.yml. Here’s a sample configuration file for a typical Java project:

# 'name' should generally be the same as the code repo name.
name: MyProject
packages:
  - path: com.mycorp.myproject
  - exclude: com.mycorp.myproject.MyClass#MyMethod
  • name Provides the project name (required)
  • packages A list of packages, classes and methods which should be instrumented.

packages

Each entry in the packages list is a YAML object which has the following keys:

  • path Java packages, clases and methods that will be included in the instrumentation.
  • exclude A list of packages, classes and methods that will be ignored. By default, all included, classes and public methods are inspected.

Running the AppMap agent

Recording tests with Maven

We recommend using the AppMap Maven plugin.

Recording tests with Gradle

We recommend using the AppMap Gradle plugin.

Other situations

Download the latest release from https://github.com/applandinc/appmap-java/releases.

The recorder is run as a Java agent. Currently, it must be started along with the JVM. This is typically done by passing the -javaagent argument to your JVM. For example:

java -javaagent:lib/appmap.jar myapp.jar

System Properties

  • appmap.config.file Path to the appmap.yml config file. Default: appmap.yml
  • appmap.output.directory Output directory for .appmap.json files. Default: ./tmp/appmap
  • appmap.debug Enable debug logging. Default: null (disabled)
  • appmap.event.valueSize Specifies the length of a value string before truncation occurs. If set to 0, truncation is disabled. Default: 1024
  • appmap.recording.auto Automatically begin recording at boot time. Default: false
  • appmap.recording.file The file name of the automatic recording to be emitted. Note that the file name will still be prefixed by appmap.output.directory. Default: $TIMESTAMP.appmap.json
  • appmap.recording.name Populates the metadata.name field of the AppMap. Default: $TIMESTAMP

Operation

Recording test cases

When running test cases with the agent attached to the JVM, methods marked with JUnit’s @Test annotation will be recorded. A new AppMap file will be created for each unique test case.

To disable recording for a particular JUnit test (for example, a performance test), list the class or methods under an exclude in appmap.yml.

Remote recording

The agent will hook an existing servlet, serving HTTP requests to toggle recording on and off. These routes are used by the AppMap browser extention.

GET /_appmap/record

Retreive the current recording status

Status 200

Body application/json

{
  "enabled": boolean
}

POST /_appmap/record

Start a new recording session

Status 200 If a new recording session was started successfully 409 If an existing recording session was already in progess

Body Empty

DELETE /_appmap/record

Stop an active recording session

Status 200 If an active recording session was stopped successfully, and the body contains AppMap JSON 404 If there was no active recording session to be stopped

Body If successful, AppMap data is returned.

application/json

{
  "version": "1.x",
  "metadata": {},
  "classMap": [],
  "events": []
}

GitHub repository

https://github.com/applandinc/appmap-java

Uploading AppMaps

https://app.land can be used to store, analyze, and share AppMaps.

For instructions on uploading, see the documentation of the AppMap Cloud CLI.


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