Maven导入本地jar包

我们知道，Maven 是通过仓库对依赖进行管理的，当 Maven 项目需要某个依赖时，只要其 POM 中声明了依赖的坐标信息，Maven 就会自动从仓库中去下载该构件使用。但在实际的开发过程中，经常会遇到一种情况：某一个项目需要依赖于存储在本地的某个 jar 包，该 jar 包无法从任何仓库中下载的，这种依赖被称为外部依赖或本地依赖。那么这种依赖是如何声明的呢？

下面我们通过一个实例实例来介绍如何导入本地 jar 包。

1. 打开令行窗口，跳转到 D:\maven 目录下，执行以下 mvn 令，创建一个名为 secondMaven 的项目。

​mvn archetype:generate -DgroupId=net.biancheng.www -DartifactId=secondMaven -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

2. 更新 secondMaven 中 App 类的代码如下。

package net.biancheng.www;
import net.biancheng.www.Util;;
public class App {
public static void main(String[] args) {
Util.printMessage("secondMaven");
}
}

由以上代码可以看出，secondMaven 中的 App 类需要使用 helloMaven 中独有的 Util 类，即 secondMaven 需要依赖于 helloMaven。

3. 跳转到 helloMaven 所在的目录，执行以下 mvn 令， 将该项目打包成 jar 文件。

mvn clean package

令执行执行结果如下。

[INFO] Scanning for projects...
[INFO]​
[INFO] --------------------< net.biancheng.www:helloMaven >--------------------
[INFO] Building helloMaven 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ helloMaven ---
[INFO] Deleting d:\maven\helloMaven\target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ helloMaven ---
[WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory d:\maven\helloMaven\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ helloMaven ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding GBK, i.e. build is platform dependent!
[INFO] Compiling 2 source files to d:\maven\helloMaven\target\classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ helloMaven ---
[WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory d:\maven\helloMaven\src\test\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ helloMaven ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding GBK, i.e. build is platform dependent!
[INFO] Compiling 1 source file to d:\maven\helloMaven\target\test-classes
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ helloMaven ---
[INFO] Surefire report directory: d:\maven\helloMaven\target\surefire-reports
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running net.biancheng.www.AppTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.016 sec
Results :
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ helloMaven ---
[INFO] Building jar: d:\maven\helloMaven\target\helloMaven-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.940 s
[INFO] Finished at: 2021-03-03T13:27:34+08:00
[INFO] ------------------------------------------------------------------------

4. 令执行完成后，进入 D:\maven\helloMaven\target 目录，可以看到 Maven 已经将 helloMaven 项目打包成 helloMaven-1.0-SNAPSHOT.jar。

5. 修改 secondMaven 中 pom.xml 的配置如下。

<project xmlns="http://maven.apache网站站点" rel="nofollow"  />     
mvn clean compile

令执行结果如下。

[WARNING]
[WARNING] Some problems were encountered while building the effective model for net.biancheng.www:secondMaven:jar:1.0-SNAPSHOT
[WARNING] 'dependencies.dependency.systemPath' for net.biancheng.www:helloMaven:jar should use a variable instead of a hard-coded path D:\maven\helloMaven\target\helloMaven-1.0-SNAPSHOT.jar @ line 23, column 16
[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] -------------------< net.biancheng.www:secondMaven >--------------------
[INFO] Building secondMaven 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ secondMaven ---
[INFO] Deleting d:\maven\secondMaven\target
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ secondMaven ---
[WARNING] Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory d:\maven\secondMaven\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ secondMaven ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding GBK, i.e. build is platform dependent!
[INFO] Compiling 1 source file to d:\maven\secondMaven\target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.030 s
[INFO] Finished at: 2021-03-03T14:05:00+08:00
[INFO] ------------------------------------------------------------------------

7. 编译完成后，执行以下令，设置临时环境变量。

set classpath=%classpath%;D:\maven\helloMaven\target\helloMaven-1.0-SNAPSHOT.jar

8. 执行以下 Java 令。

java net.biancheng.www.App

9. 结果如下图。