1. 可执行jar理解

Maven直接使用mvn package指令对项目进行打包，如果使用Java -jar xxx.jar执行运行jar文件，会出现"no main manifest attribute, in xxx.jar"（没有设置Main-Class）、ClassNotFoundException（找不到依赖包）等错误。

要想jar包能直接通过java -jar xxx.jar运行，必要条件是：

1、在jar包中的META-INF/MANIFEST.MF中指定Main-Class，这样才能确定程序的入口在哪里；

2、要能加载到依赖包。

2. 几种常见方案

所有源代码均在: https://gitee.com/shuanglin666/mvn-build-exe-jar

2.1 使用maven-jar-plugin和maven-dependency-plugin

• plugin插件配置

其中maven-jar-plugin用来打成jar包, 执行mainClass等

maven-dependency-plugin用来将依赖也打动包里面, 并且能被mainsClass识别.

详细了解, 可以将jar包unzip详细观察打包结构.

<build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-jar-plugin</artifactId><version>2.6</version><configuration><archive><manifest><addClasspath>true</addClasspath><classpathPrefix>lib/</classpathPrefix><mainClass>com.wsl.test.mvn.build.jar.dep.BootStrap1</mainClass></manifest></archive></configuration></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-dependency-plugin</artifactId><version>2.10</version><executions><execution><id>copy-dependencies</id><phase>package</phase><goals><goal>copy-dependencies</goal></goals><configuration><outputDirectory>${project.build.directory}/lib</outputDirectory></configuration></execution></executions></plugin></plugins></build>

• 执行mvn clean package打包

• 运行jar包

  java -jar java -jar mvn-jar-and-dep-1.0-SNAPSHOT.jar

2.2 使用maven-assembly-plugin

• plugin插件配置

 <build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-assembly-plugin</artifactId><version>3.1.1</version><configuration><archive><manifest><mainClass>com.wsl.test.mvn.build.assembly.BootStrap2</mainClass></manifest></archive><descriptorRefs><descriptorRef>jar-with-dependencies</descriptorRef></descriptorRefs></configuration><executions><execution><id>make-assembly</id><phase>package</phase><goals><goal>single</goal></goals></execution></executions></plugin></plugins></build>

• 执行mvn package打包

• 运行jar包

  java -jar mvn-assembly-1.0-SNAPSHOT-jar-with-dependencies.jar

2.3 使用maven-shade-plugin

• plugin插件配置

<build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-shade-plugin</artifactId><version>2.4.1</version><executions><execution><phase>package</phase><goals><goal>shade</goal></goals><configuration><transformers><transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer"><mainClass>com.wsl.test.mvn.build.shade.BootStrap3</mainClass></transformer></transformers></configuration></execution></executions></plugin></plugins></build>

• 运行mvn clean package打包

• 运行jar

  java -jar mvn-shade-1.0-SNAPSHOT.jar