詳解如何使用maven生成可以執行的jar

不依賴任何外界包，maven如何生成可以執行的jar?

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

解決過程

新建項目，僅包含一個main函數類：Xixi.java，輸出Xixi Say: hello

pom中配置為

<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>

執行mvn clean install生成jar包xixi-1.0-SNAPSHOT.jar,執行jar命令,執行反饋出錯

java -jar xixi-1.0-SNAPSHOT.jarxixi-1.0-SNAPSHOT.jar中沒有主清單屬性

對jar進行解壓縮jar xvf xixi-1.0-SNAPSHOT.jar查看對應文件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>

執行成功輸出

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

再對解壓縮後的MANIFEST.MF文件查看為

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中添加依賴，maven如何生成可執行jar?

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

解決過程

在pom中僅僅增加一個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>

在代碼中運用common包中的一個類

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

打包後直接運行出錯

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>

再次運行

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

MANIFEST.MF文件為

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

不僅使用了POM中的依賴還使用了三方的jar,maven如何生成可執行jar?

編譯過程需要對編譯插件maven-compiler-plugin做修改，運行的時候需要加上三方jar的目錄，執行命令

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

編譯解決過程

測試代碼為

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

使用mvn命令執行報錯

[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] 找不到符號

pom中添加編譯插件

<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>

打包執行

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

加上參數後即可得出結果

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

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