Modern Java Application Debugger

To debug Java applications undergoing modernization (e.g., migrating from legacy systems to Spring Boot and Angular), follow this structured process:

Debugging Process

1. •

   Check dependency conflicts first

   • •Use run_in_terminal to execute mvn dependency:tree (Maven) or gradle dependencies --scan (Gradle)
   • •Look for version conflicts between legacy and updated libraries
   • •Check for duplicate dependencies with different versions
   • •Pay special attention to Spring Boot BOM (Bill of Materials) overrides
2. •

   Verify Java version compatibility

   • •Check pom.xml or build.gradle for java.version, maven.compiler.source, or sourceCompatibility
   • •Ensure the runtime Java version matches or exceeds the compile target
   • •Use run_in_terminal to verify with java -version and mvn -version or gradle -version
   • •Watch for features that require specific Java versions (e.g., records require Java 16+)
3. •

   Enable verbose build logging

   • •For Maven: Add -X flag (e.g., mvn clean install -X)
   • •For Gradle: Add --debug or --stacktrace flag
   • •Use verbose output to identify the exact point of failure
4. •

   Check for deprecated API usage

   • •Look for calls to removed or deprecated Java APIs (common in Java 8 → 11+ migrations)
   • •Search for removed packages: javax.* → jakarta.* (Java EE → Jakarta EE)
   • •Check for removed JDK internals (e.g., sun.* packages)
5. •

   Review build tool migration issues

   • •Verify plugin versions are compatible with the new Java version
   • •Check Maven/Gradle wrapper versions (mvnw or gradlew)
   • •Ensure parent POM or dependency management sections are correctly configured
6. •

   Inspect module system conflicts

   • •Check for reflection-based code that may break with Java 9+ module system
   • •Look for IllegalAccessError or InaccessibleObjectException
   • •Add necessary --add-opens or --add-exports JVM flags if required
7. •

   Verify environment configuration

   • •Check that JAVA_HOME points to the correct JDK version
   • •Verify system properties and environment variables are set correctly
   • •Review application.properties or application.yml for configuration issues
8. •

   Analyze runtime errors

   • •Read stack traces carefully for ClassNotFoundException, NoSuchMethodError, or NoClassDefFoundError
   • •These often indicate dependency version mismatches or missing transitive dependencies
   • •Use dependency analysis tools to find the source

Common Migration Issues

• •Spring Boot 2 → 3: Requires Java 17+, Jakarta EE namespace changes, removed properties
• •Java 8 → 11+: Removed modules (JAXB, JAX-WS), different garbage collectors
• •Hibernate 5 → 6: Breaking API changes, different query behaviors
• •JUnit 4 → 5: Different annotations (@Test, @Before, @After)