Merge pull request #80 from nramc/41-add-notes-about-excluding-java-files-with-annotation

41 add notes about excluding java files with annotation

Author: nramc

docs/blog/articles/java/jacoco-exclude-code-with-annotation.md

@@ -0,0 +1,112 @@
+---
+title: Excluding Java Code from JaCoCo Code Coverage Using Annotations
+description: Explore how to exclude Java code from JaCoCo coverage using annotations.
+author: Ramachandran Nellaiyappan
+date:
+    created: 2025-03-17
+categories:
+  - Java
+tags:
+  - Java
+  - JaCoCo
+  - Code Coverage
+  - latest
+hide:
+  - toc
+links:
+  - "[Author] Ram": https://nramc.github.io/my-profile/
+---
+
+# Excluding Java Code from JaCoCo Code Coverage Using Annotations
+
+In this article, we explore how to exclude Java code from JaCoCo coverage using **annotations**.
+
+JaCoCo is a widely used code coverage tool for Java applications, helping developers assess test coverage. However,
+there are scenarios where certain methods or classes should be excluded from coverage reports, such as generated code,
+logging methods, or specific utility functions.
+
+## Why Exclude Code from JaCoCo Coverage?
+
+Some parts of the codebase should be excluded from test coverage calculations because they do not contribute to business
+logic or are externally managed.
+
+Common cases include:
+
+- **Generated Code:** Code generated by frameworks such as Lombok, JAXB, or MapStruct.
+- **Logging Methods:** Utility methods used exclusively for logging.
+- **Boilerplate Code:** Getters, setters, and other auto-generated methods.
+- **Test Utility Classes:** Helper methods used only for testing purposes.
+
+## Excluding Code Using `@Generated` Annotation
+
+JaCoCo automatically excludes methods and classes annotated with any annotation whose name ends with `Generated`.
+
+This includes standard annotations like `javax.annotation.Generated` (Java 9+) and `jakarta.annotation.Generated` (Java
+17+),
+as well as any custom annotation that follows this naming pattern.
+
+For Example, you can create a custom annotation like this:
+
+```java
+
+@Documented
+@Retention(RUNTIME)
+@Target({TYPE, METHOD})
+public @interface NoCodeCoverageGenerated {
+    String description() default "";
+}
+```
+
+```java
+import javax.annotation.Generated;
+
+public class SampleClass {
+
+    @Generated
+    public void generatedMethod() {
+        // JaCoCo will ignore this method
+    }
+
+    @NoCodeCoverageGenerated
+    public void log() {
+        // JaCoCo will ignore this method
+    }
+}
+```
+
+JaCoCo automatically detects and excludes such methods from coverage reports without requiring additional configuration.
+
+## Excluding Classes/files in `jacoco.exec`
+
+To exclude entire classes from coverage reports, configure the `jacoco-maven-plugin` as follows:
+
+```xml
+
+<plugin>
+    <groupId>org.jacoco</groupId>
+    <artifactId>jacoco-maven-plugin</artifactId>
+    <version>0.8.8</version>
+    <executions>
+        <execution>
+            <goals>
+                <goal>prepare-agent</goal>
+            </goals>
+        </execution>
+    </executions>
+    <configuration>
+        <excludes>
+            <exclude>com/example/generated/**</exclude>
+        </excludes>
+    </configuration>
+</plugin>
+```
+
+## Conclusion
+
+Excluding specific methods or classes from JaCoCo reports is crucial to maintain accurate and meaningful coverage
+metrics. Since JaCoCo automatically excludes all methods annotated with any annotation ending in `Generated`, developers
+do not need additional configuration for this behavior.
+
+By properly configuring JaCoCo, teams can focus on improving the quality of actual business logic while avoiding
+misleading coverage statistics.
+

mkdocs.yml

@@ -78,7 +78,7 @@ plugins:
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