Maven Java compilation failure

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.

Symptoms

Faultline looks for one or more of these log fragments:

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.

Why it matters

Java compilation errors block every downstream step — tests, packaging, and deployment all fail immediately. The errors are deterministic: the same code will fail every time until the source is corrected. Maven prints the compiler output verbosely enough to diagnose the exact file and line number, but the signal can be buried in pages of download progress output.

Prevention

• Run mvn clean test-compile in a pre-merge CI step to catch compile errors before the full build.
• Use a separate generate-sources verification step if your project relies on annotation processors so broken generated code is caught early.
• Avoid committing files under target/generated-sources — let Maven regenerate them on every build.

Try it locally

mvn clean test-compile
mvn clean compile
mvn clean test-compile

How Faultline detects it

Use faultline explain maven-compile-error to see the full playbook.

faultline analyze build.log
faultline explain maven-compile-error

Generated from playbooks/bundled/log/build/maven-compile-error.yaml. Do not edit directly.