4

不会还在为Jar包冲突发愁吧！！

 1 year ago
source link: https://www.51cto.com/article/721290.html
Go to the source link to view the article. You can view the picture content, updated content and better typesetting reading experience. If the link is broken, please click the button below to view the snapshot at that time.
neoserver,ios ssh client

不会还在为Jar包冲突发愁吧！！

作者：指北君 2022-10-26 08:16:58
本文中，我们学习了如何使用mvn dependency:tree和mvn dependency:analyze-duplicate命令检测Maven中的重复依赖，还学习了如何使用Maven Enforcer插件，通过应用内置规则使包含重复依赖的构建失败。

大家好，我是指北君。

在我们平时的开发过程中，常常会遇到引入各种不同的 jar 包，然后引发的 Maven 依赖冲突，今天我们来学习下如何使用 Maven 命令检测 pom.xml 中的重复依赖项。

为什么要检测重复的依赖关系

在pom.xml中, 经常引入各种不同的jar 包， 又会依赖其他的jar。特别是一些常用的工具库，比较容易出现版本冲突，例如，让我们看下这个pom.xml。

<project>
  [...]
  <dependencies>
    <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.12.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-lang3</artifactId>
      <version>3.11</version>
    </dependency>
  </dependencies>
   [...]
</project>

从上面的代码中，commons-lang3 被引用了两次，而且版本号也不一样。现在我们就来看看如何使用Maven命令来检测这些重复的依赖关系。

依赖树命令

让我们在终端运行 mvn dependency:tree的命令，看看输出结果

$ mvn dependency:tree
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.javanorth:maven-duplicate-dependencies:jar:0
.0.1-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.apache.commons:commons-lang3:jar -
> version 3.12.0 vs 3.11 @ line 14, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO]
[INFO] -------------< com.javanorth:maven-duplicate-dependencies >--------------
[INFO] Building maven-duplicate-dependencies 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ maven-duplicate-dependencies ---
[WARNING] The artifact xml-apis:xml-apis:jar:2.0.2 has been relocated to xml-apis:xml-apis:jar:1.0.b2
[INFO] com.javanorth:maven-duplicate-dependencies:jar:0.0.1-SNAPSHOT
[INFO] \- org.apache.commons:commons-lang3:jar:3.11:compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.136 s
...

我们可以看到，commons-lang3 jar的3.11版和 3.12 版同时被引入进来了，出现这种情况是因为Maven选择了pom.xml中后来出现的依赖。

依赖关系analyze-duplicate命令

现在让我们运行 mvn dependency:analyze-duplicate，看看输出输出结果。

$ mvn dependency:analyze-duplicate
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.javanorth:maven-duplicate-dependencies:jar:0
.0.1-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.apache.commons:commons-lang3:jar -
> version 3.12.0 vs 3.11 @ line 14, column 15
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO]
[INFO] -------------< com.javanorth:maven-duplicate-dependencies >--------------
[INFO] Building maven-duplicate-dependencies 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.8:analyze-duplicate (default-cli) @ maven-duplicate-dependencies ---
[WARNING] The artifact xml-apis:xml-apis:jar:2.0.2 has been relocated to xml-apis:xml-apis:jar:1.0.b2
[INFO] List of duplicate dependencies defined in <dependencies/> in your pom.xml:
        o org.apache.commons:commons-lang3:jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.835 s
。。。

我们注意到，WARNING和INFO日志语句都提到了重复依赖的存在。

如果存在重复的依赖，则构建失败

在上面的例子中，我们看到了如何检测重复的依赖关系，但BUILD仍然是成功的，但这可能导致使用了不正确的 jar 版本。

使用[Maven Enforcer Plugin]（https://maven.apache.org/enforcer/maven-enforcer-plugin/index.html），我们可以确保在存在重复依赖的情况下构建不成功。

我们需要在pom.xml中加入这个Maven插件，并加入banDuplicatePomDependencyVersions规则。

<project>
  [...]
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>3.0.0</version>
        <executions>
          <execution>
            <id>no-duplicate-declared-dependencies</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <banDuplicatePomDependencyVersions/>
              </rules>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  [...]
</project>

现在，该规则约束了我们的Maven构建。

$ mvn verify
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.javanorth:maven-duplicate-dependencies:jar:0
.0.1-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: org.apache.commons:commons-lang3:jar -
> version 3.12.0 vs 3.11 @ line 14, column 14
[WARNING]
[INFO] -------------< com.javanorth:maven-duplicate-dependencies >--------------
[INFO] Building maven-duplicate-dependencies 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-enforcer-plugin:3.0.0:enforce (no-duplicate-declared-dependencies) @ maven-duplicate-dependencies ---
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.BanDuplicatePomDependencyVersions failed with message:
Found 1 duplicate dependency declaration in this project:
 - dependencies.dependency[org.apache.commons:commons-lang3:jar] ( 2 times )

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:3.0.0:enforce (no-duplicate-declared-dependencies) on project maven-duplicate-dependencie
s:

删除重复的依赖关系

只要确定了重复的依赖关系，我们就需要在 pom.xml中删除它们，只保留那些我们项目使用的唯一依赖关系。

本文中，我们学习了如何使用mvn dependency:tree和mvn dependency:analyze-duplicate命令检测Maven中的重复依赖，还学习了如何使用Maven Enforcer插件，通过应用内置规则使包含重复依赖的构建失败。

责任编辑：武晓燕 来源： Java技术指北

report

Recommend

About Joyk


Aggregate valuable and interesting links.
Joyk means Joy of geeK