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.jar
xixi-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.MF
- Manifest-Version: 1.0
- Archiver-Version: Plexus Archiver
- Built-By: paxi
- Created-By: Apache Maven 3.3.3
- Build-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.MF
- Manifest-Version: 1.0
- Built-By: paxi
- Created-By: Apache Maven 3.3.3
- Build-Jdk: 1.8.0_121
- Main-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>
- ${project.build.directory}/libs
- </outputDirectory>
- </configuration>
- </execution>
- </executions>
- </plugin>
- </plugins>
- </build>
再次运行
- java -jar xixi-1.0-SNAPSHOT.jar
- Xixi Say: hello
MANIFEST.MF 文件为
- cat META-INF/MANIFEST.MF
- Manifest-Version: 1.0
- Built-By: paxi
- Class-Path: libs/commons-lang3-3.7.jar
- Created-By: Apache Maven 3.3.3
- Build-Jdk: 1.8.0_121
- Main-Class: com.paxi.Xixi
不仅使用了 POM 中的依赖还使用了三方的 jar,maven 如何生成可执行 jar?
编译过程需要对编译插件
maven-compiler-plugin
做修改, 运行的时候需要加上三方 jar 的目录, 执行命令
- java -jar -Djava.ext.dirs=lib/ target/xixi-1.0-SNAPSHOT.jar
- Xixi Say: hello
- Papa say:hello
编译解决过程
测试代码为
- public static void main(String[] args) {
- String words = "Xixi Say: hello";
- if (StringUtils.isNotBlank(words))
- {
- System.out.println(words);
- }
- Papa.say();
- }
使用 mvn 命令执行报错
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project xixi: Compilation failure
xixi/src/main/java/com/paxi/Xixi.java:[15,9] 找不到符号
pom 中添加编译插件
- <plugin>
- <groupId>org.apache.maven.plugins</groupId>
- <artifactId>maven-compiler-plugin</artifactId>
- <version>3.1</version>
- <configuration>
- <compilerArgs>
- <arg>-Djava.ext.dirs=lib/</arg>
- </compilerArgs>
- </configuration>
- </plugin>
打包执行
- java -jar target/xixi-1.0-SNAPSHOT.jar
- Xixi Say: hello
- Exception in thread "main" java.lang.NoClassDefFoundError: com/paxi/Papa
- at com.paxi.Xixi.main(Xixi.java:15)
Caused by: java.lang.ClassNotFoundException: com.paxi.Papa
- at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
- at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
- at sun.misc.Launcher$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.jar
- Xixi Say: hello
- Papa say:hello
来源: https://juejin.im/post/5b29318951882574d5004b50