Migrating a legacy project to Maven means restructuring it to fit Maven's standard directory layout and expressing its existing dependencies and build steps declaratively in a new pom.xml. The process is incremental — get a minimal build working first, then layer in the rest — rather than a single big-bang switch.
Key Points: • Start by creating a pom.xml defining groupId, artifactId, version, and packaging, even before every dependency is mapped. • Inventory the legacy project's libraries (often JARs committed to source control or an ad hoc lib folder) and translate them into proper Maven dependency declarations. • Reorganize source files into Maven's standard layout (src/main/java, src/main/resources, src/test/java) since Maven's plugins assume this convention. • Migrate build steps incrementally — get compilation working first, then testing, then packaging — verifying at each stage rather than converting everything at once. • Run the legacy and Maven builds in parallel for a period, comparing artifacts and test results, before fully retiring the old build process.
Example: A legacy Ant-based project with JARs checked into a /lib folder was migrated by first creating a minimal pom.xml with the correct Java version, then gradually replacing each /lib JAR with a proper Maven coordinate found via its manifest or checksum, verifying the build compiled correctly after each swap.
Interview Tip: A concise interview answer is:
"I'd start with a minimal pom.xml and get the project compiling under Maven's standard directory layout first, then incrementally migrate dependencies and build steps rather than converting everything at once. Running the old and new build processes in parallel for a while, and comparing their output, is what actually catches subtle differences before fully cutting over."