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This article will explain in detail how maven springboot packages jar to the specified directory. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

How to package the jar package to the specified directory 1. Purpose

Package the infrequent ones such as spring,druid into the lib directory so that you don't need to upload these every time you launch. Third parties or frequent changes are also packaged into their own jar packages, which will be newly packaged every time they are launched.

In this way, the original jar package of more than 100m can be changed into 2m or 3m.

As shown in the figure:

The original way of packing

The revised way:

two。 Modify pom

To explain briefly, inside the includes tag is the third party jar that enters the jar package. After unzipping the 2m package above, it is includes's package.

As shown in the figure.

ExcludeGroupIds and excludeArtifactIds are packages that are not configured in the lib directory, because the java startup loading mechanism is to load the jar package first.

Then load the external directory, if the jar package exists in two places, so the configuration is meaningless, and each time you have to republish the lib directory, so includes

And then on excludeGroupIds and excludeArtifactIds configurations.

Org.springframework.boot spring-boot-maven-plugin 2.0.5.RELEASE repackage build-info ZIP Nothing nothing com.etc etc-manage-api Com.etc etc-manage-core com.etc etc-manage-rpc-api com.sinoiov.etc.apollo Apollo-spring-boot-starter org.apache.maven.plugins maven-dependency-plugin copy package copy-dependencies Com.sinoiov.etc.apollo etc-manage-api Etc-manage-core,etc-manage-rpc-api ${project.build.directory} / lib 3. Modify startup script

Original script

Java-jar etc-manage-service-basic-2.2.0.jar

Current script (if the relative directory doesn't work, try using an absolute directory)

Configuration file and principle solution specified outside the java Dloader.path=../lib-jar etc-manage-service-basic-2.2.0.jarjar package

Modify the pom.xml file of maven

Do not copy resource files

Src/main/resources * true

Modify the packing method

Org.springframework.boot spring-boot-maven-plugin ZIP operation

Suppose application.properties and application- {profile} .properties are in / tmp/temp/config,jar file in / tmp/temp

Java-Dloader.path= file:///tmp/temp/config,demo-1.0.jar-jar demo-1.0.jar principle

Compare the differences of MANIFEST.MF files in jar package before and after `ZIP configuration

Before configuration:

Main-Class: org.springframework.boot.loader.JarLauncherStart-Class: com.chinaunicom.gateway.GatewayApplication

After configuration:

Main-Class: org.springframework.boot.loader.PropertiesLauncherStart-Class: com.chinaunicom.gateway.GatewayApplication

Find that the classloader has changed. Check all the loader implementations under the org.springframework.boot.loader package:

View five class descriptions: official documentation

JarLauncher

Launcher for JAR based archives. This launcher assumes that dependency jars are included inside a / BOOT-INF/lib directory and that application classes are included inside a / BOOT-INF/classes directory.

WarLauncher

Launcher for WAR based archives. This launcher for standard WAR archives. Supports dependencies in WEB-INF/lib as well as WEB-INF/lib-provided, classes are loaded from WEB-INF/classes.

PropertiesLauncher

Launcher for archives with user-configured classpath and main class via a properties file. This model is often more flexible and more amenable to creating well-behaved OS-level services than a model based on executable jars.

Looks in various places for a properties file to extract loader settings, defaulting to application.properties either on the current classpath or in the current working directory. The name of the properties file can be changed by setting a System property loader.config.name (e.g.-Dloader.config.name=foo will look for foo.properties. If that file doesn't exist then tries loader.config.location (with allowed prefixes classpath: and file: or any valid URL). Once that file is located turns it into Properties and extracts optional values (which can also be provided overridden as System properties in case the file doesn't exist):

Loader.path: a comma-separated list of directories (containing file resources and/or nested archives in .jar or .zip or archives) or archives to append to the classpath. BOOT-INF/classes,BOOT-INF/lib in the application archive are always used

Loader.main: the main method to delegate execution to once the class loader is set up. No default, but will fall back to looking for a Start-Class in a MANIFEST.MF, if there is one in ${loader.home} / META-INF.

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