0、工程样例
新建一个如下的Module。
Module的目录结构
Compute.java：
package com.lfqy.fatjar.util;
import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;
/**
* Created by chengxia on 2020/10/17.
*/
public class Compute {
public static Logger log4jLogger = Logger.getLogger(Compute.class);
public Compute() {
//PropertyConfigurator.configure ( "log4j.properties");
}
public static int add(int a, int b){
log4jLogger.info("Accepted: " + a + " + " + b);
return a + b;
}
public static int minus(int a, int b){
log4jLogger.info("Accepted: " + a + " - " + b);
return a - b;
}
}
App.java：
package com.lfqy.fatjar.util;
/**
* Created by chengxia on 2020/10/18.
*/
public class App {
public static void main(String []args){
int a = 3;
int b = 6;
System.out.println(Compute.add(a,b));
System.out.println(Compute.minus(a,b));
}
}
log4j.properties：
log4j.rootLogger=ALL, Log2Console, Log2File
log4j.appender.Log2Console=org.apache.log4j.ConsoleAppender
log4j.appender.Log2Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Log2Console.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
log4j.appender.Log2File = org.apache.log4j.FileAppender
log4j.appender.Log2File.File = log4j.log
log4j.appender.Log2File.Encoding=UTF-8
log4j.appender.Log2File.layout=org.apache.log4j.PatternLayout
log4j.appender.Log2File.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss}[ %p ]%m%n
log4j.appender.Log2File.append = true
这个文件需要注意，在Maven项目中，log4j.properties配置文件放在resources目录下可以缺省被识别。
pom.xml：
4.0.0
com.lfqy.fatjar
packfatjar
1.0-SNAPSHOT
log4j
log4j
1.2.11
1、简单打包
在Module的根目录执行打包命令mvn package：
$ pwd
/Users/chengxia/Developer/Java/JavaAppProject/packfatjar
$ mvn package
[INFO] Scanning for projects...
[INFO]
[INFO] ---------------------< com.lfqy.fatjar:packfatjar >---------------------
[INFO] Building packfatjar 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ packfatjar ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 2 source files to /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ packfatjar ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ packfatjar ---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ packfatjar ---
[INFO] Building jar: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.376 s
[INFO] Finished at: 2020-10-18T05:35:50+08:00
[INFO] ------------------------------------------------------------------------
$
执行完成之后，可以看到jar包已经生成：
Maven打包生成的jar包(target目录下)
这样打包完成之后，可以通过指定主类和classpath的方式运行：
$ java -classpath /Users/chengxia/.m2/repository/log4j/log4j/1.2.11/log4j-1.2.11.jar:target/packfatjar-1.0-SNAPSHOT.jar com.lfqy.fatjar.util.App
0 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 + 6
9
1 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 - 6
-3
$
从上面可以看出，这种jar包在运行时，需要指定主类并且指定依赖的jar包，比较麻烦。下面介绍Maven打包jar包时，如何制定主类。
2、通过Maven在打jar包时指定主类
我们通过修改Module的pom.xml文件可以指定打包时的主类。
4.0.0
com.lfqy.fatjar
packfatjar
1.0-SNAPSHOT
log4j
log4j
1.2.11
org.apache.maven.plugins
maven-jar-plugin
target/classes/
com.lfqy.fatjar.util.App
./log4j-1.2.11.jar
执行打包操作：
$ mvn package
[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.lfqy.fatjar:packfatjar:jar:1.0-SNAPSHOT
[WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-jar-plugin is missing. @ line 22, column 21
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO]
[INFO] ---------------------< com.lfqy.fatjar:packfatjar >---------------------
[INFO] Building packfatjar 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ packfatjar ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 2 source files to /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ packfatjar ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ packfatjar ---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ packfatjar ---
[INFO] Building jar: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.720 s
[INFO] Finished at: 2020-10-18T06:54:38+08:00
[INFO] ------------------------------------------------------------------------
$
打包完成之后，可以在jar包中看到文件META-INF/MANIFEST.MF，内容如下：
Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Built-By: chengxia
Class-Path: ./log4j-1.2.11.jar
Created-By: Apache Maven 3.6.0
Build-Jdk: 1.8.0_181
Main-Class: com.lfqy.fatjar.util.App
对于单独运行的jar包,需要在jar/META-INF/MANIFEST.MF文件里设置classpath,这样程序才能从classpath中加载文件。对于运行jar包,在环境变量里设置的classpath是无效的。这就是为什么需要在jar包中设置classpath。
注意：
这里的“.”路径指的是运行的jar包所在的目录。所以，在实际运行这个jar包时，需要将依赖的jar包同步拷贝到运行jar包所在的目录。如下示例。
$ java -jar target/pac
packfatjar-1.0-SNAPSHOT/ packfatjar-1.0-SNAPSHOT.jar
localhost:packfatjar chengxia$ java -jar target/packfatjar-1.0-SNAPSHOT.jar
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Logger
at com.lfqy.fatjar.util.Compute.(Compute.java:10)
at com.lfqy.fatjar.util.App.main(App.java:10)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Logger
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 2 more
$ cp /Users/chengxia/.m2/repository/log4j/log4j/1.2.11/log4j-1.2.11.jar target/
localhost:packfatjar chengxia$ java -jar target/packfatjar-1.0-SNAPSHOT.jar
0 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 + 6
9
2 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 - 6
-3
$
3、通过Maven生成fatjar
将jar包依赖的所有内容都打入一个jar包内，这样生成的jar包叫做fatjar。下面演示如何通过Maven打包fatjar。
首先，修改Module的pom.xml配置文件：
4.0.0
com.lfqy.fatjar
packfatjar
1.0-SNAPSHOT
log4j
log4j
1.2.11
maven-assembly-plugin
false
jar-with-dependencies
com.lfqy.fatjar.util.App
make-assembly
package
assembly
执行打包命令：
$ mvn package
[INFO] Scanning for projects...
[INFO]
[INFO] ---------------------< com.lfqy.fatjar:packfatjar >---------------------
[INFO] Building packfatjar 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ packfatjar ---
[INFO] Changes detected - recompiling the module!
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Compiling 2 source files to /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/classes
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ packfatjar ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ packfatjar ---
[INFO] No tests to run.
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ packfatjar ---
[INFO] Building jar: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
[INFO]
[INFO] >>> maven-assembly-plugin:2.2-beta-5:assembly (make-assembly) > package @ packfatjar >>>
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ packfatjar ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ packfatjar ---
[WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent!
[INFO] skip non existing resourceDirectory /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ packfatjar ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ packfatjar ---
[INFO] No tests to run.
[INFO] Skipping execution of surefire because it has already been run for this configuration
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ packfatjar ---
[INFO]
[INFO] <<< maven-assembly-plugin:2.2-beta-5:assembly (make-assembly) < package @ packfatjar <<<
[INFO]
[INFO]
[INFO] --- maven-assembly-plugin:2.2-beta-5:assembly (make-assembly) @ packfatjar ---
[INFO] Building jar: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
[WARNING] Configuration options: 'appendAssemblyId' is set to false, and 'classifier' is missing.
Instead of attaching the assembly file: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar, it will become the file for main project artifact.
NOTE: If multiple descriptors or descriptor-formats are provided for this project, the value of this file will be non-deterministic!
[WARNING] Replacing pre-existing project main-artifact file: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
with assembly file: /Users/chengxia/Developer/Java/JavaAppProject/packfatjar/target/packfatjar-1.0-SNAPSHOT.jar
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.571 s
[INFO] Finished at: 2020-10-18T09:53:08+08:00
[INFO] ------------------------------------------------------------------------
localhost:packfatjar chengxia$ tree target/
.DS_Store classes/ maven-status/ packfatjar-1.0-SNAPSHOT.jar
archive-tmp/ maven-archiver/ packfatjar-1.0-SNAPSHOT/
localhost:packfatjar chengxia$ tree target/pac
packfatjar-1.0-SNAPSHOT/ packfatjar-1.0-SNAPSHOT.jar
$
打包生成的jar包结构如下(-L 3的意思是向下指定三层目录)：
$ tree -L 3 target/packfatjar-1.0-SNAPSHOT
target/packfatjar-1.0-SNAPSHOT
├── META-INF
│ └── MANIFEST.MF
├── com
│ └── lfqy
│ └── fatjar
├── log4j.properties
└── org
└── apache
└── log4j
7 directories, 2 files
$
从上面的目录结构可以看出，对于运行所需要的log4j的内容，也被打到了同一个jar包中。jar包中看到文件META-INF/MANIFEST.MF，内容如下：
Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Built-By: chengxia
Build-Jdk: 1.8.0_181
Main-Class: com.lfqy.fatjar.util.App
接下来运行的时候，命令就简洁很多了。如下：
$ java -jar target/packfatjar-1.0-SNAPSHOT.jar
0 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 + 6
9
1 INFO [main] com.lfqy.fatjar.util.Compute - Accepted: 3 - 6
-3
$
4、参考资料
- 图解修改Maven仓库下载到本地jar包默认存储位置
- java运行jar包-设置classpath
- 执行jar包中指定main方法
- maven打包jar指定 Main-Class
- Maven项目下使用log4j