Maven Tutorial

# Maven Tutorial

>Contributors:

>

>Chen Junfeng

## Create a new project with Maven

Offcial: https://www.jetbrains.com/help/idea/maven-support.html#create_new_maven_project

1. In IDEA, click File -> New -> Project

2. Select **Maven**

   ![image-20210924215906212](assets/image-20210924215906212.png)

3. IDEA will do the rest.

4. Modify `pom.xml` to add dependencies.

   ![image-20210924220149776](assets/image-20210924220149776.png)

   ```xml

   <?xml version="1.0" encoding="UTF-8"?>

   <project xmlns="http://maven.apache.org/POM/4.0.0"

            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

            xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

       <modelVersion>4.0.0</modelVersion>

       <groupId>org.example</groupId>

       <artifactId>untitled-test</artifactId>

       <version>1.0-SNAPSHOT</version>

       <properties>

           <maven.compiler.source>16</maven.compiler.source>

           <maven.compiler.target>16</maven.compiler.target>

       </properties>

       <dependencies>

           <!-- Add your dependency here -->

       </dependencies>

   </project>

   ```

5. Add postgresql driver and gson

   How to find maven configurations for some dependency? 

   ​		Google: `maven+dependency name`, then you will get what you need.

   Gson:

   ```xml

   <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->

   <dependency>

       <groupId>com.google.code.gson</groupId>

       <artifactId>gson</artifactId>

       <version>2.8.8</version>

   </dependency>

   ```

   PostgreSQL Driver:

   ```xml

   <!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->

   <dependency>

       <groupId>org.postgresql</groupId>

       <artifactId>postgresql</artifactId>

       <version>42.2.24</version>

   </dependency>

   ```

6. `pom.xml`:

   ```xml

   <?xml version="1.0" encoding="UTF-8"?>

   <project xmlns="http://maven.apache.org/POM/4.0.0"

            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

            xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

       <modelVersion>4.0.0</modelVersion>

       <groupId>org.example</groupId>

       <artifactId>untitled-test</artifactId>

       <version>1.0-SNAPSHOT</version>

       <properties>

           <maven.compiler.source>16</maven.compiler.source>

           <maven.compiler.target>16</maven.compiler.target>

       </properties>

       <dependencies>

           <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->

           <dependency>

               <groupId>com.google.code.gson</groupId>

               <artifactId>gson</artifactId>

               <version>2.8.8</version>

           </dependency>

           <!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->

           <dependency>

               <groupId>org.postgresql</groupId>

               <artifactId>postgresql</artifactId>

               <version>42.2.24</version>

           </dependency>

       </dependencies>

   </project>

   ```

7. Load Maven Changes

   <img src="assets/image-20210924220915752.png" alt="image-20210924220915752" style="zoom: 67%;" />

   When there is no red in the dependencies section, all dependencies are resolved.

8. If you can't find this button, there is a shortcut in idea based IDE to find an action.

   Press the RIGHT SHIFT twice, input `maven`, then use TAB to switch tabs to **Actions**.

   <img src="assets/image-20210924221143602.png" alt="image-20210924221143602" style="zoom: 33%;" />

   ​	You will find the Maven action, then press ENTER to open it.

   <img src="assets/image-20210924221313921.png" alt="image-20210924221313921" style="zoom:50%;" />

   Select **Reload Project** and maven will resolve all dependencies.

## Add Maven support to existing project

https://www.jetbrains.com/help/idea/convert-a-regular-project-into-a-maven-project.html

## If you have Internet connection issue

Thanks to GFW.

Get a good proxy which brings you to the Internet, then see: https://blog.csdn.net/c5113620/article/details/103064538