Java API Compliance Checker

Java API Compliance Checker (JAPICC) is a tool for checking backward binary and source-level compatibility of a Java library API. The tool checks classes declarations of old and new versions and analyzes changes that may break compatibility: removed methods, removed class fields, added abstract methods, etc. The HTML compatibility report generated by this tool includes separate sections for both source and binary compatibility analysis and exact error messages of the jvm and the compiler for each break found in the API.

Binary incompatibility may result in crashing or incorrect behavior of existing clients built with an old version of a library when they are running with a new one. Source incompatibility may result in recompilation errors with a new library version. The tool is intended for developers of software libraries and Linux maintainers who are interested in ensuring backward compatibility, i.e. allow old clients to run or to be recompiled with newer library versions.

The Scala language is supported since 1.7 version of the tool.

Java 9 is supported since 2.4 version of the tool.

The tool is a core of the Java API Tracker project.

Downloads

The latest release can be downloaded from this page.

Read-only access to the latest development version:

License

This program is free software. You may use, redistribute and/or modify it under the terms of the GNU LGPL

Supported Platforms

Dependencies

• JDK or OpenJDK - development files (javap, javac)
• Perl 5

Installation

The tool is ready-to-use after extracting the archive.

You can also use a Makefile to install the tool into the system:

 sudo make install prefix=PREFIX [/usr, /usr/local, ...] 

This command will install the japi-compliance-checker program into the PREFIX/bin system directory and private modules into the PREFIX/share.

To verify that the tool is installed correctly and it works on your host run:

 japi-compliance-checker -test 

Usage

 japi-compliance-checker -lib NAME V1.jar V2.jar 

The compatibility report will be generated to:

 compat_reports/NAME/V1_to_V2/compat_report.html 

Usage (Multiple Archives)

<version>
    1.0
</version>

<archives>
    /path1/to/JAR(s)/
    /path2/to/JAR(s)/
       ...
</archives>

Command to compare two versions of a library:

japi-compliance-checker -lib NAME -old V1.xml -new V2.xml

The compatibility report will be generated to:

compat_reports/NAME/V1_to_V2/compat_report.html

Examples

See more report examples at https://abi-laboratory.pro/java/tracker/.

Detectable Compatibility Problems

• Problems with Data Types
  • Classes and Interfaces
    • removed classes or interfaces
    • removed fields
    • removed methods
    • change of a field type
    • change of a field access level
    • change of a field attributes (final, static, etc.)
    • change of a constant field value
    • changes in fields (recursive analysis)
    • added/removed abstract methods
    • added/removed super-interfaces
  • Classes
    • added/removed super-classes
    • moving a method up class hierarchy
    • overridden methods
      
      
• Problems with Methods
  • changed attributes (static, final, synchronized, abstract, etc.)
  • changed access level
  • added/removed exceptions
    
    
• Problems with Annotations
  • removed annotations

Test Suite

japi-compliance-checker -test

There are about 80 basic tests in the test suite.

API Dumps

The API dump consists of:

• Types Information
  • Attributes (name, package, access, base types, etc.)
  • Fields (name, type, access, specifiers, etc.)
  • Etc.
• Symbols Information
  • Attributes (name, mangled name, package, access, specifiers, etc.)
  • Parameters (name, type, position, etc.)
  • Etc.
• Etc.

To create an API dump use -dump option:

japi-compliance-checker -lib NAME -dump LIB.jar -dump-path ./API.dump

To compare API dumps pass them instead Java archives:

japi-compliance-checker -lib NAME -old API-0.dump -new API-1.dump

Report Format

• Test Info - The library name and compared version numbers.
• Test Results - Verdict on compatibility. Number of archives, classes and methods checked by the tool.
• Problem Summary - Classification of compatibility problems.
• Added Methods - The list of added methods.
• Removed Methods - The list of removed methods.
• Problems with Data Types - List of compatibility problems caused by changes in data types (divided by the severity level: High, Medium, Low). List of affected methods.
• Problems with Methods - The list of compatibility problems caused by changes in method parameters and attributes (divided by the severity level).
• Other Changes in Data Types - The list of compatible changes in data types.
• Other Changes in Methods - The list of compatible changes in methods.

Verdict on Compatibility

Error Codes

Similar Tools

• Clirr - checks Java libraries for binary and source compatibility with older releases
• Revapi - API analysis and change tracking tool
• Japicmp - a tool to compare two versions of a jar archive
• Japitools - test for compatibility between Java APIs
• Jour - Java API compatibility testing tools
• Japi-checker - a java API backward compatibility checker which works at binary level
• SigTest - Oracle's SigTest signature testing and API conformance tool

Bugs

Maintainers

Changes

Articles

• “Evolving Java-based APIs: Achieving API Binary Compatibility”, Jim des Rivières
• “Binary Compatibility”, Java Language Specification
• “Backwards compatibility with Java bytecode editing”, Dan Amlund Thomsen
• “Kinds of Compatibility: Source, Binary, and Behavioral”, Joseph D. Darcy's Oracle Weblog