详解如何使用maven生成可以执行的jar

不依赖任何外界包，maven如何生成可以执行的jar?

pom中不包含任何引用的情况下，只需要在pom中添加 maven-jar-plugin即可。

解决过程

新建项目，仅包含一个main函数类：Xixi.java，输出Xixi Say: hello

pom中配置为

<groupId>com.paxi</groupId> <artifactId>xixi</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <name>xixi</name> <url>http://maven.apache.org</url> <properties>  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties>

执行 mvn clean install 生成jar包 xixi-1.0-SNAPSHOT.jar,执行jar命令,执行反馈出错

java -jar xixi-1.0-SNAPSHOT.jarxixi-1.0-SNAPSHOT.jar中没有主清单属性

对jar进行解压缩jar xvf xixi-1.0-SNAPSHOT.jar查看对应文件MANIFEST.MF

cat META-INF/MANIFEST.MFManifest-Version: 1.0Archiver-Version: Plexus ArchiverBuilt-By: paxiCreated-By: Apache Maven 3.3.3Build-Jdk: 1.8.0_121

在pom中添加插件 maven-jar-plugin

<build>  <plugins>   <plugin>    <groupId>org.apache.maven.plugins</groupId>    <artifactId>maven-jar-plugin</artifactId>    <version>3.1.0</version>    <configuration>     <archive>      <manifest>       <mainClass>com.paxi.Xixi</mainClass>      </manifest>     </archive>    </configuration>   </plugin>  </plugins> </build>

执行成功输出

java -jar xixi-1.0-SNAPSHOT.jar
Xixi Say: hello

再对解压缩后的MANIFEST.MF文件查看为

cat META-INF/MANIFEST.MFManifest-Version: 1.0Built-By: paxiCreated-By: Apache Maven 3.3.3Build-Jdk: 1.8.0_121Main-Class: com.paxi.Xixi //新增

在pom中添加依赖，maven如何生成可执行jar?

需要使用插件maven-dependency-plugin 和 maven-jar-plugin。

解决过程

在pom中仅仅增加一个apache-commons包

<groupId>com.paxi</groupId> <artifactId>xixi</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <name>xixi</name> <url>http://maven.apache.org</url> <properties>  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies>   <dependency>    <groupId>org.apache.commons</groupId>    <artifactId>commons-lang3</artifactId>    <version>3.7</version>  </dependency> </dependencies>

在代码中运用common包中的一个类

public static void main(String[] args) {    String words = "Xixi Say: hello";    if (StringUtils.isNotBlank(words))    {      System.out.println(words);    }  }

打包后直接运行出错

java -jar xixi-1.0-SNAPSHOT.jar
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang3/StringUtils
at com.paxi.Xixi.main(Xixi.java:11)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang3.StringUtils
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 1 more

在pom中增加插件

<build>  <plugins>   <plugin>    <groupId>org.apache.maven.plugins</groupId>    <artifactId>maven-jar-plugin</artifactId>    <version>3.1.0</version>    <configuration>     <archive>      <manifest>       <addClasspath>true</addClasspath>       <mainClass>com.paxi.Xixi</mainClass>       <classpathPrefix>libs/</classpathPrefix>      </manifest>     </archive>    </configuration>   </plugin>   <plugin>    <groupId>org.apache.maven.plugins</groupId>    <artifactId>maven-dependency-plugin</artifactId>    <version>3.1.1</version>    <executions>     <execution>      <id>copy-dependencies</id>      <phase>package</phase>      <goals>       <goal>copy-dependencies</goal>      </goals>      <configuration>       <outputDirectory>        ${project.build.directory}/libs       </outputDirectory>      </configuration>     </execution>    </executions>   </plugin>  </plugins> </build>

再次运行

java -jar xixi-1.0-SNAPSHOT.jarXixi Say: hello

MANIFEST.MF文件为

cat META-INF/MANIFEST.MFManifest-Version: 1.0Built-By: paxiClass-Path: libs/commons-lang3-3.7.jarCreated-By: Apache Maven 3.3.3Build-Jdk: 1.8.0_121Main-Class: com.paxi.Xixi

不仅使用了POM中的依赖还使用了三方的jar,maven如何生成可执行jar?

编译过程需要对编译插件maven-compiler-plugin做修改，运行的时候需要加上三方jar的目录，执行命令

java -jar -Djava.ext.dirs=lib/ target/xixi-1.0-SNAPSHOT.jarXixi Say: helloPapa say:hello

编译解决过程

测试代码为

public static void main(String[] args) {    String words = "Xixi Say: hello";    if (StringUtils.isNotBlank(words))    {      System.out.println(words);    }    Papa.say();  }

使用mvn命令执行报错

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project xixi: Compilation failure
xixi/src/main/java/com/paxi/Xixi.java:[15,9] 找不到符号

pom中添加编译插件

<plugin>    <groupId>org.apache.maven.plugins</groupId>    <artifactId>maven-compiler-plugin</artifactId>    <version>3.1</version>    <configuration>     <compilerArgs>      <arg>-Djava.ext.dirs=lib/</arg>     </compilerArgs>    </configuration>   </plugin>

打包执行

java -jar target/xixi-1.0-SNAPSHOT.jarXixi Say: helloException in thread "main" java.lang.NoClassDefFoundError: com/paxi/Papa  at com.paxi.Xixi.main(Xixi.java:15)Caused by: java.lang.ClassNotFoundException: com.paxi.Papa  at java.net.URLClassLoader.findClass(URLClassLoader.java:381)  at java.lang.ClassLoader.loadClass(ClassLoader.java:424)  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)  at java.lang.ClassLoader.loadClass(ClassLoader.java:357)  ... 1 more

加上参数后即可得出结果

java -jar -Djava.ext.dirs=lib/ target/xixi-1.0-SNAPSHOT.jarXixi Say: helloPapa say:hello

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