JarCastingAppMap 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 AppLand browser extension to start, stop, and upload recordings.
- Record the code with
AppMap.recordAPI, 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 Visual Studio Code.
The second option is to upload them to the AppLand server using the AppLand 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
Maven
We recommend using the AppMap Maven plugin.
Other than Maven
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
Gradle
test {
jvmArgs "-javaagent:$rootDir/lib/appmap.jar"
}
System Properties
appmap.config.filePath to theappmap.ymlconfig file. Default: appmap.ymlappmap.output.directoryOutput directory for.appmap.jsonfiles. Default:./tmp/appmapappmap.debugEnable debug logging. Default:null(disabled)appmap.event.valueSizeSpecifies the length of a value string before truncation occurs. If set to0, truncation is disabled. Default:1024
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 AppLand 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, scenario data is returned.
application/json
{
"version": "1.x",
"metadata": {},
"classMap": [],
"events": []
}
Developing
The Spring PetClinic provides a convenient way to develop on appmap-java.
Obtain the spring-petclinic JAR file, and launch it with the AppLand Java agent:
export PETCLINIC_DIR=<path-to-petclinic>
java -Dappmap.debug \
-javaagent:build/libs/appmap.jar \
-Dappmap.config.file=test/appmap.yml \
-jar $(PETCLINIC_DIR)/target/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
You can use Java remote debug settings to attach a debugger:
export PETCLINIC_DIR=<path-to-petclinic>
java -Dappmap.debug \
-javaagent:build/libs/appmap.jar \
-Dappmap.config.file=test/appmap.yml \
-Xdebug \
-Xrunjdwp:server=y,transport=dt_socket,address=5005,suspend=y \
-jar $PETCLINIC_DIR/target/spring-petclinic-2.2.0.BUILD-SNAPSHOT.jar
Building
Artifacts will be written to build/libs. Use appmap.jar as your agent.
./gradlew build
Testing
Unit tests are run via the test task.
Docker is required to run integration tests. Run the following command:
./bin/test
Visual Studio Code integration
The AppMap for Visual Studio Code extension is a great way to onboard developers to new code, and troubleshoot hard-to-understand bugs with visuals.
Uploading AppMaps
https://app.land can be used to store, analyze, and share AppMaps.
For instructions on uploading, see the documentation of the AppLand CLI.