Springboot jar包外指定配置文件及原理

• 解决方案：
  
  修改maven的pom.xml文件

不拷贝资源文件
<resources>
    <resource>
        <directory>src/main/resources</directory>
        <excludes>
            <exclude>*</exclude>
        </excludes>
        <filtering>true</filtering>
    </resource>
</resources>

修改打包方式
<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <layout>ZIP</layout>
    </configuration>
</plugin>

• 运行
  
  假设application.properties和application-{profile}.properties都在/tmp/temp/config，jar文件在/tmp/temp
  
  java -Dloader.path=file:///tmp/temp/config,demo-1.0.jar -jar demo-1.0.jar

---

• 原理
  
  对比jar包中MANIFEST.MF文件在`ZIP配置前后的区别
  
  配置前：

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

     配置后：

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

     发现是类加载器变了，查看org.springframework.boot.loader包下所有加载器实现：

     查看五个类描述：官方文档

• 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.

• spring-boot-maven-plugin帮助
  
  对zip格式说明
  
  对jar和war说明