Maven：库文件版本冲突（主要就是jar包版本冲突）解决方法

男娘i 2023-07-04 12:36 160阅读 0赞

在解决库版本冲突（主要就是jar包版本冲突）之前，首先要明白Maven对于使用相同库的哪个版本，它是通过什么策略决定的。主要是两个策略:

>  *  **nearest-wins**  路径最近的获胜
>  *  **the first declaration wins**  最先声明的获胜

下面通过两个例子来说明：

### 1、nearest-wins ###

> mvn dependency:tree -Dverbose -Dincludes=commons-collections:commons-collections -f D:\\pom.xml

> \[INFO\] \[dependency:tree\]  
> \[INFO\] org.apache.maven.plugins:maven-dependency-plugin:maven-plugin:2.0-alpha-5-SNAPSHOT  
> \[INFO\] +- org.apache.maven.reporting:maven-reporting-impl:jar:2.0.4:compile  
> \[INFO\] |  \\- commons-validator:commons-validator:jar:1.2.0:compile  
> \[INFO\] |     \\- commons-digester:commons-digester:jar:1.6:compile  
> \[INFO\] |        \\- (commons-collections:commons-collections:jar:2.1:compile - omitted for conflict with 2.0)  
> \[INFO\] \\- org.apache.maven.doxia:doxia-site-renderer:jar:1.0-alpha-8:compile  
> \[INFO\]    \\- org.codehaus.plexus:plexus-velocity:jar:1.1.3:compile  
> \[INFO\]       \\- commons-collections:commons-collections:jar:2.0:compile

可以看到commons-collections:jar:2.0只用3层就可以找到，而commons-collections:jar:2.1需要经过4层才能打到，因此就选择使用最近的那个，也就是commons-collections:jar:2.0

### 2、the first declaration wins ###

官方文档中的解释：  
if two dependency versions are at the same depth in the dependency tree, the first declaration wins.

> mvn dependency:tree -Dverbose -Dincludes=log4j:log4j -f D:\\pom.xml

> \[INFO\] \[dependency:tree \{execution: default-cli\}\]  
> \[INFO\] com.openboxes.renderingservice:common:jar:1.0  
> \[INFO\] +- org.springframework:spring:jar:2.0.4:compile  
> \[INFO\] |  \\- commons-logging:commons-logging:jar:1.1:compile  
> \[INFO\] |     \\- log4j:log4j:jar:1.2.12:compile  
> \[INFO\] \\- it.mycompany.portal:server:jar:1.5-SNAPSHOT:compile  
> \[INFO\]    \\- org.slf4j:slf4j-log4j12:jar:1.1.0:compile  
> \[INFO\]       \\- (log4j:log4j:jar:1.2.13:compile - omitted for conflict with 1.2.12)

log4j:jar:1.2.12和log4j:jar:1.2.13都只用3层就可以找到，但log4j:jar:1.2.12先出现的，因此使用log4j:jar:1.2.12

**对于1，有以下3种解决方法：**  
**a**、将commons-collections:jar:2.1直接在<dependencies>中声明，这样它就在第1层，比commons-collections:jar:2.0的路径短，会直接被采用。

> <dependencies>  
>     <dependency>  
>         <groupId>commons-collections</groupId>  
>         <artifactId>commons-collections</artifactId>  
>         <version>2.1</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>org.apache.maven.reporting</groupId>  
>         <artifactId>maven-reporting-impl</artifactId>  
>         <version>2.0.4</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>org.apache.maven.doxia</groupId>  
>         <artifactId>doxia-site-renderer</artifactId>  
>         <version>1.0-alpha-8</version>  
>     </dependency>  
> </dependencies>

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp_size_16_color_FFFFFF_t_70][]

**b**、将commons-collections:jar:2.1直接在<dependencyManagement>中声明。

> <dependencyManagement>  
>     <dependencies>  
>         <dependency>  
>             <groupId>commons-collections</groupId>  
>             <artifactId>commons-collections</artifactId>  
>             <version>2.1</version>  
>         </dependency>  
>     </dependencies>  
> </dependencyManagement>
> 
> <dependencies>  
>     <dependency>  
>         <groupId>org.apache.maven.reporting</groupId>  
>         <artifactId>maven-reporting-impl</artifactId>  
>         <version>2.0.4</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>org.apache.maven.doxia</groupId>  
>         <artifactId>doxia-site-renderer</artifactId>  
>         <version>1.0-alpha-8</version>  
>     </dependency>  
> </dependencies>

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp_size_16_color_FFFFFF_t_70 1][]  
**c**、使用<exclusion>将commons-collections:jar:2.0从doxia-site-renderer:jar:1.0-alpha-8中排除，这样就只能采用commons-collections:jar:2.1

> <dependencies>  
>     <dependency>  
>         <groupId>org.apache.maven.reporting</groupId>  
>         <artifactId>maven-reporting-impl</artifactId>  
>         <version>2.0.4</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>org.apache.maven.doxia</groupId>  
>         <artifactId>doxia-site-renderer</artifactId>  
>         <version>1.0-alpha-8</version>  
>         <exclusions>  
>             <exclusion>  
>                 <groupId>commons-collections</groupId>  
>                 <artifactId>commons-collections</artifactId>  
>             </exclusion>  
>         </exclusions>  
>     </dependency>  
> </dependencies>

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp_size_16_color_FFFFFF_t_70 2][]

**对于2，除了能使用对于1的方法解决外，还可以使用如下方法：**  
如果这两个不同版本库的根路径不相同，则可以调整这2个根路径对应的库的声明在pom.xml中的顺序。

调整前：

> <dependencies>  
>     <dependency>  
>         <groupId>org.springframework</groupId>  
>         <artifactId>spring</artifactId>  
>         <version>2.0.4</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>it.mycompany.portal</groupId>  
>         <artifactId>server</artifactId>  
>         <version>1.5-SNAPSHOT:</version>  
>     </dependency>  
> </dependencies>

调整后：

> <dependencies>  
>     <dependency>  
>         <groupId>it.mycompany.portal</groupId>  
>         <artifactId>server</artifactId>  
>         <version>1.5-SNAPSHOT:</version>  
>     </dependency>  
>     <dependency>  
>         <groupId>org.springframework</groupId>  
>         <artifactId>spring</artifactId>  
>         <version>2.0.4</version>  
>     </dependency>  
> </dependencies>

**参考文档**

Introduction to the Dependency Mechanism  
[http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html][http_maven.apache.org_guides_introduction_introduction-to-dependency-mechanism.html]

Resolving conflicts using the dependency tree  
[http://maven.apache.org/plugins/maven-dependency-plugin/examples/resolving-conflicts-using-the-dependency-tree.html][http_maven.apache.org_plugins_maven-dependency-plugin_examples_resolving-conflicts-using-the-dependency-tree.html]

Interpreting “omitted for conflict” in maven 2 dependency tree  
[https://stackoverflow.com/questions/7742312/interpreting-omitted-for-conflict-in-maven-2-dependency-tree][https_stackoverflow.com_questions_7742312_interpreting-omitted-for-conflict-in-maven-2-dependency-tree]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/2020021114043630.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/2020021114084445.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25ldHllYXhp,size_16,color_FFFFFF,t_70
[http_maven.apache.org_guides_introduction_introduction-to-dependency-mechanism.html]: http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html
[http_maven.apache.org_plugins_maven-dependency-plugin_examples_resolving-conflicts-using-the-dependency-tree.html]: http://maven.apache.org/plugins/maven-dependency-plugin/examples/resolving-conflicts-using-the-dependency-tree.html
[https_stackoverflow.com_questions_7742312_interpreting-omitted-for-conflict-in-maven-2-dependency-tree]: https://stackoverflow.com/questions/7742312/interpreting-omitted-for-conflict-in-maven-2-dependency-tree