Getting started with maven (1)

Now basically many projects start to use maven to build projects, instead of placing jar packages directly under the lib folder, it is still necessary to learn to master maven.

For maven. This article mainly introduces a few points. If everyone understands it, you can refer to this mind map and review it again. After all, the knowledge will be forgotten if it is not used for a long time.
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1. What is maven

Maven's Apache open source project is a project build tool and is also used for dependency management.

Second, the benefits of maven

1. Since the project built by maven has no jar package, the size of the project must be that the maven project is relatively small.
2. The jar package is uniformly handed over to maven for management.
3. Maven can also build projects.

Maven is mainly about project construction and dependency (jar package) management

Three, maven installation

Prerequisites for maven program installation: The maven program is developed in java, and its operation depends on jdk.

1. First go to Maven's official website and download the Maven package at http://maven.apache.org/download.cgi
2. After downloading and unzipping, configure the environment variables, similar to the JDK environment variable configuration (as shown in the figure)
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3. Query maven version information

4. Configure local warehouse
Find config/setting.xml in the decompressed directory, mine is E:\app\apache-maven-3.5.3\conf\setting.xml
Mainly modify 2 places
4.1 Modify Local warehouse path

4.2 is modified to Alibaba Cloud image

    <mirror>
        <id>nexus-aliyun</id>
        <mirrorOf>*</mirrorOf>
        <name>Nexus aliyun</name>
        <url>http://maven.aliyun.com/nexus/content/groups/public</url>
    </mirror>

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4.4 Copy the setting.xml you just set to the local warehouse path you set, mine is E:\dev_maven
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5. What are the types of warehouses
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Fourth, use maven to build the project

Here I created it with eclipse

1. Eclipse configuration

1.1 Configure the maven program
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1.2 Configure the userSetting, know the warehouse location

1.3 Build the index to find the jar package (Window->show view->maven Repository)

2. Start to create a project
2.1 Select the normal project - Maven Project here, click next

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2.2 Select war as the packaging method and complete.
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2.3 web.xml is missing and an error is reported

At this point, an error will be reported, and WEB-INF/web.xml needs to be created under src-main-webapp

Directory Structure
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web.xml content

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">

    
    
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>

</web-app>

Also create an index.xml_(src\main\webapp\index.html)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>Hello maven</h1>
</body>
</html>

Set the jdk compiled version to 1.8. The default is 1.5
Modify the pom file

<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>com.zhb</groupId>
  <artifactId>maven_hello</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  
  
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>  
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>