Maven打包可执行jar包方法

原文：How to Create an Executable JAR with Maven

方法一：使用maven-jar-plugin和maven-dependency-plugin

首先，maven-jar-plugin的作用是配置mainClass和指定classpath。

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <configuration>
        <archive>
            <manifest>
                <addClasspath>true</addClasspath>
                <classpathPrefix>libs/</classpathPrefix>
                <mainClass>
                    org.baeldung.executable.ExecutableMavenJar
                </mainClass>
            </manifest>
        </archive>
    </configuration>
</plugin>

Manifest-Version: 1.0                                                                                                                                         
Archiver-Version: Plexus Archiver
Built-By: michealyang
Class-Path: libs/jetty-server-9.4.7.v20170914.jar lib/javax.servlet-api
 -3.1.0.jar libs/jetty-http-9.4.7.v20170914.jar 
Created-By: Apache Maven 3.3.9
Build-Jdk: 1.8.0_162-ea
Main-Class: com.michealyang.jetty.embeded.EmbeddedJettyServer

其次，maven-dependency-plugin会把所依赖的jar包copy到指定目录

<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}/libs
                </outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>

executions中的配置都很重要，按照上面的配置来就行了。outputDirectory指定了要将所依赖的jar包copy到哪个目录。要与maven-jar-plugin中的classpathPrefix一致。

执行如下命令，即可打包：

mvn package

打包结果是，自己写的Class在jar包中，所依赖的jar包在libs目录中:

├── embedded-jetty-1.0.0-SNAPSHOT.jar
├── lib
│ ├── jetty-server-9.4.7.v20170914.jar
│ ├── jetty-http-9.4.7.v20170914.jar

执行如下命令即可启动jar包：

java -jar embedded-jetty-1.0.0-SNAPSHOT.jar

优点

有诸多配置项，很自由，每个步骤都可控

缺点

打成的最终jar包中没有所依赖的jar包。依赖跟自己的代码不在一个jar包中。部署或者移动的时候，要考虑到多个文件，比较麻烦

方法二：使用maven-assembly-plugin (推荐)

maven-assembly-plugin可以将所有的东西都打包到一个jar包中。

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-assembly-plugin</artifactId>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>single</goal>
            </goals>
            <configuration>
                <archive>
                <manifest>
                    <mainClass>
                        com.michealyang.jetty.embeded.EmbeddedJettyServer
                    </mainClass>
                </manifest>
                </archive>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
            </configuration>
        </execution>
    </executions>
</plugin>

执行mvn package后，会在target文件夹下生成两个jar包，一个是不带依赖的jar包，一个是后缀有-dependencies带有依赖的jar包，如：

May 31 16:42 embedded-jetty-1.0.0-SNAPSHOT-jar-with-dependencies.jar

May 31 16:42 embedded-jetty-1.0.0-SNAPSHOT.jar

启动时，直接执行即可：

java -jar embedded-jetty-1.0.0-SNAPSHOT-jar-with-dependencies.jar

优点

所有的东西都打到一个jar包中，很方便

缺点

配置项少，不自由。

方法三：使用maven-shade-plugin

跟maven-assembly-plugin类似，都可以将所有的东西都打包到一个jar包中。

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <executions>
        <execution>
            <goals>
                <goal>shade</goal>
            </goals>
            <configuration>
                <shadedArtifactAttached>true</shadedArtifactAttached>
                <transformers>
                    <transformer implementation=
                      "org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                        <mainClass>com.michealyang.jetty.embeded.EmbeddedJettyServer</mainClass>
                </transformer>
            </transformers>
        </configuration>
        </execution>
    </executions>
</plugin>

执行mvn package后，会在target文件夹下生成两个jar包，一个是不带依赖的jar包，一个是后缀有-shaded带有依赖的jar包，如：

May 31 16:53 embedded-jetty-1.0.0-SNAPSHOT-shaded.jar

May 31 16:53 embedded-jetty-1.0.0-SNAPSHOT.jar

启动时，直接执行即可：

java -jar embedded-jetty-1.0.0-SNAPSHOT-jar-with-shaded.jar

优点

功能同maven-assembly-plugin，但比前者强大

缺点

配置起来太麻烦。当你需要高级功能的时候，更是麻烦的不要不要的。

方法四：使用onejar-maven-plugin

This provides custom classloader that knows how to load classes and resources from jars inside an archive, instead of from jars in the filesystem.

<plugin>
    <groupId>com.jolira</groupId>
    <artifactId>onejar-maven-plugin</artifactId>
    <executions>
        <execution>
            <configuration>
                <mainClass>org.baeldung.executable.
                  ExecutableMavenJar</mainClass>
                <attachToBuild>true</attachToBuild>
                <filename>
                  ${project.build.finalName}.${project.packaging}
                </filename>
            </configuration>
            <goals>
                <goal>one-jar</goal>
            </goals>
        </execution>
    </executions>
</plugin>

优点

clean delegation model, allows classes to be at the top-level of the One Jar, supports external jars and can support Native libraries

缺点

not actively supported since 2012

方法五：使用spring-boot-maven-plugin

能同时打可执行jar包和war包

This allows to package executable jar or war archives and run an application “in-place”.

需要maven版本不低于3.2

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
            <configuration>
                <classifier>spring-boot</classifier>
                <mainClass>
                  org.baeldung.executable.ExecutableMavenJar
                </mainClass>
            </configuration>
        </execution>
    </executions>
</plugin>

两个重点：

goal要写成repackage

classifier要写成spring-boot

优点

dependencies inside a jar file, you can run it in every accessible location, advanced control of packaging your artifact, with excluding dependencies from the jar file etc., packaging of war files as well

缺点

添加了一些不必要的Spring和Spring Boot依赖

方法六：使用tomcat7-maven-plugin

可打包成一个web工程类型的jar包。其实是内嵌了一个tomcat在里面。

<plugin>
    <groupId>org.apache.tomcat.maven</groupId>
    <artifactId>tomcat7-maven-plugin</artifactId>
    <version>2.0</version>
    <executions>
        <execution>
            <id>tomcat-run</id>
            <goals>
                <goal>exec-war-only</goal>
            </goals>
            <phase>package</phase>
            <configuration>
                <path>/</path>
                <enableNaming>false</enableNaming>
                <finalName>webapp.jar</finalName>
                <charset>utf-8</charset>
            </configuration>
        </execution>
    </executions>
</plugin>

The goal is set as exec-war-only, path to your server is specified inside configuration tag, with additional properties, like finalName, charset etc. To build a jar, run man package, which will result in creating webapp.jar in your target directory. To run

To run the application, just write this in your console: java -jar target/webapp.jar and try to test it by specifying the localhost:8080/ in a browser.

优点

只有一个jar包

缺点

打包出的文件很大。因为里面内嵌了一个tomcat