depends

The missing linker for the JVM.

Problem statement

Have you ever gotten an error like this:

java.lang.NoClassDefFoundError: com/google/gson/JsonParseException

    at io.kubernetes.client.ApiClient.<init>(ApiClient.java:85)
    at io.kubernetes.client.util.ClientBuilder.build(ClientBuilder.java:202)
    at io.kubernetes.client.util.Config.defaultClient(Config.java:104)
Caused by: java.lang.ClassNotFoundException: com.google.gson.JsonParseException
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 26 more

Then spent hours trying different versions of dependencies until it magically goes away?

Solution

Just run:

java -jar build/libs/depends-1.0-SNAPSHOT.jar com.mycompany.app:my-app:1.0-SNAPSHOT --filter=JsonParseException

And get a helpful report of what's broken:

broken apis:
         com.fasterxml.jackson.core.JsonParseException.getMessage()Ljava/lang/String; is only present in 
        [com.fasterxml.jackson.core:jackson-core [2.9.3, 2.9.5, 2.9.4, 2.9.6]]

        com.fasterxml.jackson.core.JsonParseException.<init>(Lcom/fasterxml/jackson/core/JsonParser;Ljava/lang/String;Ljava/lang/Throwable;)V is only present in 
        [com.fasterxml.jackson.core:jackson-core [2.9.3, 2.9.5, 2.9.4, 2.7.8, 2.9.6]]

        com.fasterxml.jackson.core.JsonParseException.<init>(Lcom/fasterxml/jackson/core/JsonParser;Ljava/lang/String;)V is only present in 
        [com.fasterxml.jackson.core:jackson-core [2.9.3, 2.9.5, 2.9.4, 2.7.8, 2.9.6]]

        com.fasterxml.jackson.core.JsonParseException.<init>(Lcom/fasterxml/jackson/core/JsonParser;Ljava/lang/String;Lcom/fasterxml/jackson/core/JsonLocation;)V is only present in 
        [com.fasterxml.jackson.core:jackson-core [2.9.3, 2.9.5, 2.9.4, 2.7.8, 2.9.6]]

Then pick a version from the list!

Building

git clone https://github.com/bgard6977/depends.git
cd dependes
./gradlew build
# This will create depends.jar
# Now, You'll need to run mvn install or gradle install on your project, to put build your code and put the resulting jar into your maven/gradle local cache. 
# After you've done artifact install, you can run depends on it like that:
java -jar build/libs/depends-1.0-SNAPSHOT.jar com.mycompany.app:my-app:1.0-SNAPSHOT --filter=JsonParseException
# com.mycompany.app:my-app:1.0-SNAPSHOT is the artifact you want to check.

How it works

1. It uses ShrinkWrap Resolver to build a dependency graph of your project.
2. It scans through the classes in each jar and uses ASM4 to find function invocations.
3. It builds a map of all cross-module function calls.
4. It assumes any function called from an external module is a public API.
5. It compares all the versions of each module to see which methods are not present in all versions.
6. It filters these by a given search term.
7. Finally, it prints a report to help you figure out which version to use when a dependency conflict arrises.

Roadmap

1. Count all the broken calls, and recommend the version of each library most likely to not have missing method exceptions at run time.
2. Produce a report to name-and-shame semver violations.
3. Convert this project into a Gradle ResolutionStrategy so it Just Works.