Maven Java compilation failure

April 30, 2026 · View on GitHub

Playbook ID: maven-compile-error Category: build Severity: high Tags: java, maven, compile, build, javac

What this failure means

The Maven compiler plugin failed during compilation. Common causes are duplicate class definitions, missing symbols from a recently changed API, or generated sources that are no longer in sync with the code.

Common log signals

COMPILATION ERROR :
duplicate class:
is already defined in class
cannot find symbol
Compilation failure: Compilation failure:
Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin

Diagnosis

Maven surfaced a COMPILATION ERROR from the maven-compiler-plugin. The javac errors underneath it identify the root cause:

  • duplicate class — the same class is defined more than once, often because generated source directories are also committed, or a class was moved without removing the original.
  • is already defined in class — an inner class or enum constant appears twice in the same compilation unit. Usually caused by a failed merge or a code generator run that appended to an existing file.
  • cannot find symbol — a method, field, or type that the code references no longer exists. Frequently triggered by a Lombok, MapStruct, or other annotation-processor model change that happened in a different commit.

Fix steps

Duplicate class

  1. Search for all copies of the class file:

    find . -name "DuplicateClass.java" -not -path "*/target/*"

  2. Remove the stale copy or the generated source directory from pom.xml <sourceDirectory> / <testSourceDirectory>.

  3. Clean the build cache:

    mvn clean compile

Cannot find symbol

  1. Check whether the missing symbol was removed or renamed in a recent commit:

    git log --oneline -5 -- path/to/ChangedClass.java

  2. Re-run the annotation processor (Lombok, MapStruct, etc.) if the symbol is generated:

    mvn clean generate-sources compile

  3. Verify that the IDE-generated target/generated-sources is not excluded from the Maven source root configuration.

Validation

  • mvn clean test-compile — must exit 0 with no COMPILATION ERROR lines.
  • Re-run the CI job and confirm the [ERROR] COMPILATION ERROR line is absent.

Likely files to inspect

  • pom.xml
  • src/main/java/**/*.java
  • src/test/java/**/*.java

Run Faultline

faultline analyze build.log
faultline explain maven-compile-error
faultline workflow build.log --json --mode agent

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Generated from playbooks/bundled/log/build/maven-compile-error.yaml. Do not edit directly — run make docs-generate.