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MAVEN USEFUL COMMANDS
Maven commands to quickly get you going.

Category: Maven · Type: cheatsheet
Official docs: https://maven.apache.org/

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## What is Maven?

**Maven** is a powerful build automation and project management tool primarily used for Java projects. This guide covers frequently used Maven commands for dependency management, debugging, and troubleshooting.

**⚡ Key Features**
- Local JAR installation
- Dependency debugging
- Multi-module builds
- Profile management
- Offline mode support

**🎯 Use Cases**
- Installing proprietary JARs
- Debugging dependency conflicts
- Managing multi-module projects
- Optimizing build performance
- Troubleshooting build issues

---

## 🧩 Install Local JAR

Manually install a dependency when it **cannot be downloaded from Maven Central** (Oracle, IBM, internal JARs).

```bash
mvn install:install-file \
  -Dfile=ojdbc8.jar \
  -DgroupId=com.oracle.database.jdbc \
  -DartifactId=ojdbc8 \
  -Dversion=19.3.0.0 \
  -Dpackaging=jar
```

### Common Use Cases
- Oracle JDBC drivers
- Telecom / vendor SDKs
- Internal utilities not published yet

## 🏢 Deploy to Nexus/Artifactory

Publish any standalone JAR to your **internal Maven repository**.

```bash
mvn deploy:deploy-file \
  -Durl=http://nexus.myorg.com/repository/maven-releases/ \
  -DrepositoryId=nexus \
  -Dfile=my-util.jar \
  -DgroupId=com.myorg.util \
  -DartifactId=my-util \
  -Dversion=1.0.0 \
  -Dpackaging=jar
```

### Requirements
- Configure `repositoryId` in `settings.xml`
- Ensure credentials are set up
- Use releases repo for stable versions

## 🔍 Debug Dependencies

### View Full Tree
```bash
mvn dependency:tree
```

### Filter Specific Dependency
```bash
mvn dependency:tree -Dincludes=com.fasterxml.jackson.core
```

### Verbose Mode
```bash
mvn dependency:tree -Dverbose
```

### Show Conflicts
```bash
mvn dependency:tree -Dverbose | grep "omitted for conflict"
```

## 🔄 Force Update Dependencies

Force Maven to download latest SNAPSHOT and release versions.

```bash
mvn clean install -U
```

### When to Use
- SNAPSHOT dependencies not updating
- Corrupted local repository
- After changing remote repository URLs

## 🧱 Build Specific Module

Build only a specific module in a multi-module project.

```bash
mvn -pl module-name -am clean install
```

### Flags
| Flag | Description |
|------|-------------|
| `-pl` | Project list - specify module(s) |
| `-am` | Also make - build required dependencies |
| `-amd` | Also make dependents - build dependent modules |

### Examples
```bash
# Build single module
mvn -pl service-api clean install

# Build multiple modules
mvn -pl service-api,service-impl clean install

# Build module and dependents
mvn -pl shared-utils -amd clean install
```

## 🚫 Skip Tests

### Skip Test Execution
```bash
mvn clean install -DskipTests
```

### Skip Compilation & Execution
```bash
mvn clean install -Dmaven.test.skip=true
```

### Difference
- `skipTests`: Compiles but doesn't run
- `maven.test.skip`: Skips everything

## 🧪 Run Specific Tests

### Single Test Class
```bash
mvn -Dtest=LoginTest test
```

### Pattern Matching
```bash
mvn -Dtest=User*Test test
```

### Specific Test Method
```bash
mvn -Dtest=LoginTest#shouldLoginWorks test
```

### Multiple Tests
```bash
mvn -Dtest=LoginTest,UserTest test
```

## 🧹 Fix Corrupted Dependencies

### Delete Specific Library
```bash
rm -rf ~/.m2/repository/com/oracle
```

### Purge Entire Local Repo
```bash
mvn dependency:purge-local-repository
```

### Re-download All
```bash
mvn dependency:purge-local-repository -DreResolve=true
```

## 📜 Effective POM

View the final POM after all inheritance and interpolation.

```bash
mvn help:effective-pom
```

### Save to File
```bash
mvn help:effective-pom > effective-pom.xml
```

### Why Use It
- Debug property resolution
- See inherited configurations
- Verify profile activation

## 🔧 List Active Plugins

```bash
mvn help:effective-pom | grep "<plugin>"
```

### All Available Plugins
```bash
mvn help:describe -Dplugin=compiler
```

## 🐞 Debug Mode

Enable debug logging for CI/CD troubleshooting.

```bash
mvn clean install -X
```

### Show Stack Traces
```bash
mvn clean install -e
```

## 🔐 Fix SSL/Certificate Issues

### Import Certificate
```bash
keytool -import -alias nexus \
  -file nexus.crt \
  -keystore $JAVA_HOME/jre/lib/security/cacerts \
  -storepass changeit
```

### Disable SSL Verification (Development Only)
```bash
mvn clean install -Dmaven.wagon.http.ssl.insecure=true \
  -Dmaven.wagon.http.ssl.allowall=true
```

## 🧵 Work with Profiles

### List All Profiles
```bash
mvn help:all-profiles
```

### Show Active Profiles
```bash
mvn help:active-profiles
```

### Build with Profile
```bash
mvn clean install -Pdev
```

### Multiple Profiles
```bash
mvn clean install -Pdev,fast-tests
```

## 📦 Offline Mode

Download all dependencies for offline use.

```bash
mvn dependency:go-offline
```

### Build Offline
```bash
mvn clean install -o
```

### Use Cases
- CI/CD with dependency caching
- Development without internet
- Air-gapped environments

## 🎯 Clean Specific Targets

### Clean Generated Sources
```bash
mvn clean:clean@clean-generated
```

### Clean Without Deleting Logs
```bash
mvn clean -Dclean.exclude=logs/**
```

### Deep Clean
```bash
mvn clean install -U -DskipTests
```

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