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SpringBoot项目使用Maven打包：
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
执行mvn clean package命令后，生成应用jar，用压缩文件查看，maven自动生成了MANIFEST.MF文件：
Manifest-Version: 1.0 Implementation-Title: github-demo
Implementation-Version: 2.1-SNAPSHOT Start-Class:
com.gitlab.example.demo.DemoApplication Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/ Build-Jdk-Spec: 1.8 Spring-Boot-Version:
2.2.1.RELEASE Created-By: Maven Archiver 3.4.0 Main-Class:
org.springframework.boot.loader.JarLauncher
依赖的jar也在应用jar 中，位于BOOT-INF/lib/目录下。使用java -jar 即可运行这个应用jar包。
为了提高部署的效率，需要把应用jar包跟依赖jar包分开，当项目中没有新增依赖的jar包时，只需把应用单独打包出来就行，这样应用jar包的大小会小很多。
这需要maven-jar-plugin插件，改变默认的打包方式；还需要maven-dependency-plugin，把依赖的jar包打包。pom文件主要部分如下：
<build> <plugins> <!--设置应用 Main 参数启动依赖查找的地址指向外部 lib 文件夹--> <plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId> <configuration> <archive> <manifest>
<addClasspath>true</addClasspath> <!-- 项目所依赖的jar位于同一级的lib目录下-->
<classpathPrefix>lib/</classpathPrefix> </manifest> </archive> </configuration>
</plugin> <!--设置 SpringBoot 打包插件不包含任何 Jar 依赖包--> <plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId> <configuration> <includes>
<include> <groupId>nothing</groupId> <artifactId>nothing</artifactId>
</include> </includes> </configuration> </plugin> <!--设置将 lib 拷贝到应用 Jar 外面-->
<plugin> <groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId> <executions> <execution>
<id>copy-dependencies</id> <phase>prepare-package</phase> <goals>
<goal>copy-dependencies</goal> </goals> <configuration>
<outputDirectory>${project.build.directory}/lib</outputDirectory>
</configuration> </execution> </executions> </plugin> </plugins> </build>
目的就是为了把依赖的jar包放到target/lib目录下，在MANIFEST.MF文件中自动添加Class-Path属性，指向所依赖的jar包:
Manifest-Version: 1.0 Implementation-Title: github-demo
Implementation-Version: 2.4-SNAPSHOT Start-Class:
com.gitlab.example.demo.DemoApplication Spring-Boot-Classes: BOOT-INF/classes/
Class-Path: lib/spring-boot-starter-web-2.2.1.RELEASE.jar lib/spring-b
oot-starter-2.2.1.RELEASE.jar lib/spring-boot-2.2.1.RELEASE.jar lib/s
pring-boot-autoconfigure-2.2.1.RELEASE.jar lib/spring-boot-starter-lo
gging-2.2.1.RELEASE.jar lib/logback-classic-1.2.3.jar lib/logback-cor
e-1.2.3.jar lib/log4j-to-slf4j-2.12.1.jar lib/log4j-api-2.12.1.jar li
b/jul-to-slf4j-1.7.29.jar lib/jakarta.annotation-api-1.3.5.jar lib/sn
akeyaml-1.25.jar lib/spring-boot-starter-json-2.2.1.RELEASE.jar lib/j
ackson-databind-2.10.0.jar lib/jackson-annotations-2.10.0.jar lib/jac
kson-core-2.10.0.jar lib/jackson-datatype-jdk8-2.10.0.jar lib/jackson
-datatype-jsr310-2.10.0.jar lib/jackson-module-parameter-names-2.10.0 .jar
lib/spring-boot-starter-tomcat-2.2.1.RELEASE.jar lib/tomcat-embe
d-core-9.0.27.jar lib/tomcat-embed-el-9.0.27.jar lib/tomcat-embed-web
socket-9.0.27.jar lib/spring-boot-starter-validation-2.2.1.RELEASE.ja r
lib/jakarta.validation-api-2.0.1.jar lib/hibernate-validator-6.0.18 .Final.jar
lib/jboss-logging-3.4.1.Final.jar lib/classmate-1.5.1.jar
lib/spring-web-5.2.1.RELEASE.jar lib/spring-beans-5.2.1.RELEASE.jar l
ib/spring-webmvc-5.2.1.RELEASE.jar lib/spring-aop-5.2.1.RELEASE.jar l
ib/spring-context-5.2.1.RELEASE.jar lib/spring-expression-5.2.1.RELEA SE.jar
lib/slf4j-api-1.7.29.jar lib/spring-core-5.2.1.RELEASE.jar lib
/spring-jcl-5.2.1.RELEASE.jar Spring-Boot-Lib: BOOT-INF/lib/ Build-Jdk-Spec:
1.8 Spring-Boot-Version: 2.2.1.RELEASE Created-By: Maven Archiver 3.4.0
Main-Class: org.springframework.boot.loader.JarLauncher
这样，当打出来的应用jar包，跟依赖jar包的lib文件夹放在同一个目录下时，使用java -jar就可以运行应用jar包了。