Maven

Install Maven

Ubuntu

sudo apt install maven

Manually

  1. 下载Binary tar.gz archive文件
  2. 安装
mkdir ~/.java
cd ~/.java
tar zxvf apache-maven-3.5.4-bin.tar.gz

vi ~/.bash_profile

export MAVEN_HOME=/Users/yizhenchen/.java/apache-maven-3.5.4
export M2_HOME=$MAVEN_HOME
export PATH=$PATH:$MAVEN_HOME/bin

source ~/.bash_profile
  1. 检查是否安装成功
mvn -v
echo $M2_HOME

首次运行完mvn后会在"~“目录下创建”.m2"文件夹，作为本地仓库

配置Maven

修改配置文件

  • $MAVEN_HOME/conf/settings.xml
  • ~/.m2/settings.xml

使用Maven

在项目中添加pom.xml文件

  • groupId: 一般为package名
  • artifactId： 一般为项目名
  • version： 版本

目录结构：

  • Project
    • pom.xml
    • src
      • main
        • java
        • resources
      • test
        • java
        • resources
    • target
<groupId>here.there</groupId>
<artifactId>MavenTest</artifactId>
<version>1.0</version>

命令

  • clean：清空target目录
  • complie：编译工程
  • package：执行打包
  • install：发布到仓库

运行

mvn exec:java -Dexec.mainClass="package.Main"

# 避免 `IllegalThreadStateException`
mvn exec:java -Dexec.mainClass="package.Main" -Dexec.cleanupDaemonThreads=false

依赖关系

  • compile: 编译时需要用到该jar包（默认）
  • test: 编译Test时需要用到该jar包
  • runtime: 编译时不需要，但运行时需要用到
  • provided: 编译时需要用到，但运行时由JDK或某个服务器提供

SNAPSHOT

SNAPSHOT结尾的版本号会被Maven视为开发版本，开发版本每次都会重复下载。

镜像仓库

添加镜像仓库

<!-- 阿里云仓库 -->
<mirror>
  <id>alimaven</id>
  <mirrorOf>central</mirrorOf>
  <name>aliyun maven</name>
  <url>http://maven.aliyun.com/nexus/content/repositories/central/</url>
</mirror>

<!-- 中央仓库1 -->
  <mirror>
  <id>repo1</id>
  <mirrorOf>central</mirrorOf>
  <name>Human Readable Name for this Mirror.</name>
  <url>http://repo1.maven.org/maven2/</url>
</mirror>

<!-- 中央仓库2 -->
  <mirror>
  <id>repo2</id>
  <mirrorOf>central</mirrorOf>
  <name>Human Readable Name for this Mirror.</name>
  <url>http://repo2.maven.org/maven2/</url>
</mirror>

搜索第三方组件

https://search.maven.org/

https://mvnrepository.com

Jar 打包

主要有三个plugins可以提供打包jar的功能，jar-plugin/shade-plugin/assembly-plugin，具体区别见以下链接：

Difference between maven plugins ( assembly-plugins , jar-plugins , shaded-plugins)

maven-jar-plugin

使用 maven-jar-plugin插件打包。不会复制dependency到目标文件夹，因此需要在manifest中指定classpath路径

Set Up The Classpath

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <configuration>
        <archive>
            <manifest>
                <!-- 在manifest中添加classpath -->
                <addClasspath>true</addClasspath>
                <!-- 指定classpath路径 -->
                <classpathPrefix>/Users/yizhenchen/.m2/repository/</classpathPrefix>
                <!-- 使用Repository-Style的路径 -->
                <classpathLayoutType>repository</classpathLayoutType>
                <mainClass>Main</mainClass>
            </manifest>
        </archive>
    </configuration>
</plugin>

maven-dependency-plugin

使用maven-dependency-plugin 插件将依赖包复制到 ./target/lib/ 中

Copying project dependencies

<build>
    <plugins>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>
                        <mainClass>Main</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <executions>
                <execution>
                    <id>copy-dependencies</id>
                    <phase>package</phase>
                    <goals>
                        <goal>copy-dependencies</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${project.build.directory}/lib</outputDirectory>
                    </configuration>
                </execution>
            </executions>
        </plugin>

    </plugins>
</build>

maven-assembly-plugin

适用于较少denpendencies的项目，因为同名文件会有覆盖的问题

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>3.3.0</version>
    <configuration>
        <!-- get all project dependencies -->
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
        <!-- MainClass in mainfest make a executable jar -->
        <archive>
            <manifest>
                <mainClass>MainClass</mainClass>
            </manifest>
        </archive>
    </configuration>
    <executions>
        <execution>
            <id>make-assembly</id>
            <!-- bind to the packaging phase -->
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
</plugin>

maven-shade-plugin

使用 maven-shade-plugin 打包

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.2.4</version>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
              	<goal>shade</goal>
            </goals>
            <configuration>
                <transformers>
                    <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                      	<mainClass>Main</mainClass>
                    </transformer>
                </transformers>
            </configuration>
        </execution>
    </executions>
</plugin>

常用 Dependencies

hive udf dependency

<dependencies>
  <dependency>
    <groupId>org.apache.hive</groupId>
    <artifactId>hive-exec</artifactId>
    <version>0.12.0</version>
  </dependency>
  <dependency>
    <groupId>org.apache.hadoop</groupId>
    <artifactId>hadoop-common</artifactId>
    <version>2.5.0</version>
  </dependency>
</dependencies>

Jackson

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>${jackson-version}</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>${jackson-version}</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>${jackson-version}</version>
</dependency>

问题

  1. Warning: File encoding has not been set, using platform encoding UTF-8

在pom.xml中加上

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
  1. Maven中引用了Dependencies，但是在Idea运行时报错找不到依赖

重启IntelliJ Idea，会在External Libraries中下载好包，再运行即可

References