Maven First Project

Create Maven Project

Generate a project using Maven Archetype

Maven provides project templates (Archetypes) to quickly generate a standard project structure. The most commonly used is maven-archetype-quickstart (basic Java project template).

Execute the command:

mvn archetype:generate \
    -DgroupId=com.example \
    -DartifactId=my-first-app \
    -DarchetypeArtifactId=maven-archetype-quickstart \
    -DinteractiveMode=false

Parameter Description:

Parameter	Description
`-DgroupId`	Organization name (e.g., company domain in reverse)
`-DartifactId`	Project name (becomes the project folder name)
`-DarchetypeArtifactId`	The template used (`quickstart`is a basic Java project)
`-DinteractiveMode=false`	Non-interactive mode (avoid manual confirmation)

The project structure generated after execution:

my-first-app/
├── pom.xml           # Maven 项目配置文件
├── src/
│   ├── main/         # 主代码目录
│   │   └── java/     # Java 源代码
│   │       └── com/example/App.java  # 自动生成的示例类
│   └── test/        # 测试代码目录
│       └── java/     # 测试类
│           └── com/example/AppTest.java  # 自动生成的测试类

Project Structure Analysis

Detailed Explanation of pom.xml

This is Maven's core configuration file, defining the project's basic information and dependencies.

Example of the generated pom.xml:

<project>
    <!-- POM 模型版本，固定 4.0.0 -->
    <modelVersion>4.0.0</modelVersion>

    <!-- 项目坐标（唯一标识） -->
    <groupId>com.example</groupId>
    <artifactId>my-first-app</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!-- 项目打包方式（默认 jar，也可以是 war、pom 等） -->
    <packaging>jar</packaging>

    <!-- 项目名称和 URL（可选） -->
    <name>my-first-app</name>
    <url>http://www.example.com</url>

    <!-- 依赖管理 -->
    <dependencies>
        <!-- JUnit 测试依赖 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>  <!-- 仅用于测试 -->
        </dependency>
    </dependencies>
</project>

Source Code Structure

Directory	Purpose
`src/main/java`	Main Java source code
`src/main/resources`	Configuration files (such as`application.properties`）
`src/test/java`	Test code
`src/test/resources`	Test resource files

Example code:

Main class App.java

Example

package com.example;

public class App {
public static void main(String[] args) {
System.out.println("Hello Maven!");
}
}

Test class AppTest.java:

Example

package com.example;

import org.junit.Test;
import static org.junit.Assert.*;

public class AppTest {
@Test
public void testApp() {
assertTrue(true); // Example test
}
}

Building and Running

Common Maven Commands

Command	Purpose
`mvn compile`	Compile source code
`mvn test`	Run tests
`mvn package`	Package (generates`.jar`file)
`mvn install`	Install to local repository (for other projects to depend on)
`mvn clean`	Clean`target`directory

Complete Build Process

1. Compile the project:

mvn compile

The compiled .class files will be placed in the target/classes directory.

2. Run tests:

mvn test

Execute the test classes under src/test/java.

Test reports are generated in target/surefire-reports.

3. Package:

mvn package

Generates target/my-first-app-1.0-SNAPSHOT.jar.

4. Run the program:

java -cp target/my-first-app-1.0-SNAPSHOT.jar com.example.App

5. Output:

Hello Maven!

Extension: Modifying the Project

Adding Dependencies

For example, addGsonfor JSON processing:

Modify pom.xml:

<dependencies>
    <!-- 原有 JUnit 依赖 -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>

    <!-- 新增 Gson 依赖 -->
    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.9</version>
    </dependency>
</dependencies>

Run mvn compile, Maven will automatically download Gson.

Modify the main class to use Gson

Example

package com.example;

import com.google.gson.Gson;

public class App {
public static void main(String[] args) {
Gson gson = new Gson();
String json = gson.toJson("Hello Maven with Gson!");
System.out.println(json);
}
}

Repackage and run:

mvn package
java -cp target/my-first-app-1.0-SNAPSHOT.jar com.example.App

Output:

"Hello Maven with Gson!"

Common Problems

Dependency download failure

Cause: Network issue or repository unavailable.

Solution:

Check the network connection.

Configure a domestic mirror repository (e.g., Alibaba Cloud):

<!-- 在 settings.xml 或 pom.xml 中配置 -->
<mirror>
    <id>aliyun</id>
    <url>https://maven.aliyun.com/repository/public</url>
    <mirrorOf>central</mirrorOf>
</mirror>

Alibaba Cloud repository introduction:https://developer.aliyun.com/mvn/guide。

Compilation version issue

Error: javac: invalid target release: 11

Solution: Specify the Java version in pom.xml:

<properties>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
</properties>

Summary

Create a project：mvn archetype:generateGenerate a standard structure.
Project structure：
- pom.xmlDefine dependencies and configuration.
- src/main/javaPlace main code,src/test/javaPlace test code.
Build commands：
- mvn compile → mvn test → mvn package。
Run：java -jarorjava -cpExecute.jarfile.

Other Extensions