BOM簡介
BOM(Bill of Materials)是由Maven提供的功能,它通過定義一整套相互兼容的jar包版本集合,使用時只需要依賴該BOM文件,即可放心的使用需要的依賴jar包,且無需再指定版本號。BOM的維護方負責版本升級,並保證BOM中定義的jar包版本之間的兼容性。
爲什麼要使用BOM
使用BOM除了可以方便使用者在聲明依賴的客戶端時不需要指定版本號外,最主要的原因是可以解決依賴衝突,如考慮以下的依賴場景:
項目A依賴項目B 2.1和項目C 1.2版本:
項目B 2.1依賴項目D 1.1版本;
項目C 1.2依賴項目D 1.3版本;
在該例中,項目A對於項目D的依賴就會出現衝突,按照maven dependency mediation的規則,最後生效的可能是:項目A中會依賴到項目D1.1版本(就近原則,取決於路徑和依賴的先後,和Maven版本有關係)。
在這種情況下,由於項目C依賴1.3版本的項目D,但是在運行時生效的確是1.1版本,所以在運行時很容易產生問題,如 NoSuchMethodError, ClassNotFoundException等。
如何定義BOM
BOM本質上是一個普通的POM文件,區別是對於使用方而言,生效的只有<dependencyManagement>
這一個部分。只需要在<dependencyManagement>
定義對外發布的客戶端版本即可:
<?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>com.ydj.qd</groupId>
<artifactId>inf-bom</artifactId>
<version>1.0</version>
<packaging>pom</packaging>
<name>inf-bom</name>
<description>第三方jar包統一管理</description>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring.version>4.3.15.RELEASE</spring.version>
</properties>
<dependencyManagement>
<dependencies>
<!-- 阿里 -->
<!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.12</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.aliyun.mns/aliyun-sdk-mns -->
<dependency>
<groupId>com.aliyun.mns</groupId>
<artifactId>aliyun-sdk-mns</artifactId>
<version>1.1.8</version>
<classifier>jar-with-dependencies</classifier>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.29</version>
</dependency>
<!-- Apache -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.3.2</version>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.2</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.1</version>
</dependency>
<dependency>
<groupId>commons-beanutils</groupId>
<artifactId>commons-beanutils</artifactId>
<version>1.9.1</version>
</dependency>
<!-- 谷歌 -->
<!-- https://mvnrepository.com/artifact/com.google.guava/guava -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>27.0.1-jre</version>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.5</version>
</dependency>
<!-- 常用工具 -->
<dependency>
<groupId>joda-time</groupId>
<artifactId>joda-time</artifactId>
<version>2.7</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.14.4</version>
</dependency>
</dependencies>
</dependencyManagement>
<build>
</build>
<distributionManagement>
<repository>
<id>maven-releases</id>
<name>maven-releases</name>
<url>http://mvn.ydj.com/repository/maven-releases/</url>
</repository>
<snapshotRepository>
<id>maven-snapshots</id>
<name>maven-snapshots</name>
<url>http://mvn.ydj.com/repository/maven-snapshots/</url>
</snapshotRepository>
</distributionManagement>
</project>
項目使用方法
- 在你的項目主pom.xml文件中
<dependencyManagement></dependencyManagement>
節點下首位處加入如下:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>com.jlcx.qd</groupId>
<artifactId>inf-bom</artifactId>
<version>${version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
...
</dependency>
</dependencies>
</dependencyManagement>
- 在需要使用相關JAR包的pom.xml文件中
<dependencies></dependencies>
節點下引入如下:
<dependencies>
...
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
</dependency>
....
</dependencies>
如果需要使用不同於當前bom中所維護的jar包版本,則加上<version>
覆蓋即可,如:
<dependencies>
...
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.1</version>
</dependency>
....
</dependencies>