What is maven used for?

The functions of maven are: 1. Add the corresponding configuration in the file, and maven will automatically download the corresponding jar package; 2. Download dependencies, as long as other jar packages that the configured jar package depends on will be It downloads automatically; 3. You can package war or jar projects directly through it.

The role of maven: add the corresponding configuration in the file, maven will automatically download the corresponding jar package; to download dependencies, as long as the configured jar package Other dependent jar packages will be automatically downloaded by it; war or jar projects can be packaged directly through it.

1. Help you download the jar package

The maven project will have a pom.xml file. In this file, as long as You add the corresponding configuration, and it will automatically download the corresponding jar package for you. You don’t need to search everywhere for the jar package you need

The following is the demonstration configuration file pom.xml

<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/maven-v4_0_0.xsd">   
<modelVersion>4.0.0</modelVersion>    
<groupId>exam</groupId>    
<artifactId>exam_3</artifactId>    
<packaging>war</packaging>    
<version>0.0.1-SNAPSHOT</version>    
<dependencies>     
<dependency>       
<groupId>junit</groupId>       
<artifactId>junit</artifactId>       
<version>3.8.1</version>       
<scope>test</scope>     
</dependency>     
<dependency>         
<groupId>org.springframework</groupId>         
<artifactId>spring-web</artifactId>         
<version>3.0.5.RELEASE</version>     
</dependency>     
<dependency>         
<groupId>org.springframework</groupId>         
<artifactId>spring-webmvc</artifactId>         
<version>3.0.5.RELEASE</version>     
</dependency>     
</dependencies> 
</project>

Above The main thing to look at is the content in the node.
Each is configured inside,
Project name: org.springframework
Project module: < artifactId>spring-webmvc
Project version: 3.0.5.RELEASE
Maven will pass, project name-project module-project version to maven code on the Internet Download the corresponding jar package from the library.
So this is one of the functions of maven, to help you download jar packages

2. Find dependencies and help you download dependencies

Finding jar packages is the first Basic functions, looking for dependencies in this are functions based on this.

In the maven code base, each jar package also has its own pom.xml file, and this file will also have a configuration, as long as the jar package you configure depends on other jar packages It will be automatically downloaded by maven.

For example:

 <dependency>         
 <groupId>org.springframework</groupId>       
 <artifactId>spring-core</artifactId>        
 <version>2.6</version>   
 </dependency>

You want maven to help you download the spring-core-2.6.jar package
And this jar package needs to use the commons-logging.jar package,
This is called dependency, spring-core-2.6.jar depends on commons-logging.jar.
This is the second role of maven, to help you download dependency packages.

3. Hot deployment, hot compilation

means that when your web project is running, the modified code can be directly accepted by the web server, and it will not You need to restart the server or redeploy the code, and you can package the war or jar project directly through maven.

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