all-in-one jar 包。maven-jar-plugin转化的包和spring-boot-maven-plugin自动生成的包之間的随便有别，是fat jar中一般曾加了两个分，独一部门是lib总目录，摆放的是Maven依耐的jar包文件夹,第二个部门是spring boot loader相关的类。
fat jar //目录结构
├─BOOT-INF
│ ├─classes
│ └─lib
├─META-INF
│ ├─maven
│ ├─app.properties
│ ├─MANIFEST.MF
└─org
└─springframework
└─boot
└─loader
├─archive
├─data
├─jar
└─util
spring-boot-maven-plugin岗位体制，而spring-boot-maven-plugin归于自定议3d浏览器插件，所以说我们的又不得不明白，Maven的自定议3d浏览器插件是是怎样的工作的
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
org.springframework.boot.maven.RepackageMojo#execute，该具体方法的具体方法是跳转了org.springframework.boot.maven.RepackageMojo#repackage
private void repackage() throws MojoExecutionException {
//抓取选用maven-jar-plugin产生的jar，最终能够的排序将加带.orignal尾缀
Artifact source = getSourceArtifact();
//结果是文本，即Fat jar
File target = getTargetFile();
//获得再次封装器，将再次封装成可来执行jar资料
Repackager repackager = getRepackager(source.getFile());
//寻找并过滤程序创业项目自动运行时依赖感的jar
Set<Artifact> artifacts = filterDependencies(this.project.getArtifacts(),
getFilters(getAdditionalFilters()));
//将artifacts换为成libraries
Libraries libraries = new ArtifactsLibraries(artifacts, this.requiresUnpack,
getLog());
try {
//带来Spring Boot打火代码
LaunchScript launchScript = getLaunchScript();
//制定重复做好逻辑思维，转化第四fat jar
repackager.repackage(target, libraries, launchScript);
}
catch (IOException ex) {
throw new MojoExecutionException(ex.getMessage(), ex);
}
//将source最新成 xxx.jar.orignal相关文件
updateArtifact(source, target, repackager.getBackupFile());
}
org.springframework.boot.maven.RepackageMojo#getRepackager一个方法步骤，要知道Repackager是如果转为的，也就具体要猜测出自有的压缩道理。
private Repackager getRepackager(File source) {
Repackager repackager = new Repackager(source, this.layoutFactory);
repackager.addMainClassTimeoutWarningListener(
new LoggingMainClassTimeoutWarningListener());
//装置main class的标题，如果不制定的时候则会找到一包涵main办法的类，repacke最终也会装置org.springframework.boot.loader.JarLauncher
repackager.setMainClass(this.mainClass);
if (this.layout != null) {
getLog().info("Layout: " + this.layout);
//重要关心的话下layout 最中调用了 org.springframework.boot.loader.tools.Layouts.Jar
repackager.setLayout(this.layout.layout());
}
return repackager;
}
/**
* Executable JAR layout.
*/
public static class Jar implements RepackagingLayout {
@Override
public String getLauncherClassName() {
return "org.springframework.boot.loader.JarLauncher";
}
@Override
public String getLibraryDestination(String libr𒉰aryName, LibraryScope🦄 scope) {
return "BOOT-INF/lib/";
}
@Override
public String getClassesLocation() {
return "";
}
@Override
public String getRepackagedClassesLocation() {
return "BOOT-INF/classes/";
}
@Override
public boolean isExecutable() {
return true;
}
}
org.springframework.boot.loader.JarLauncher，从昵称推论，这很应该是回可制定jar信息的初始化类。
Manifest-Version: 1.0
Implementation-Title: oneday-auth-server
Implementation-Version: 1.0.0-SNAPSHOT
Archiver-Version: Plexus Archiver
Built-By: oneday
Implementation-Vendor-Id: com.oneday
Spring-Boot-Version: 2.1.3.RELEASE
Main-Class: org.springframework.boot.loader.JarLauncher
Start-Class: com.oneday.auth.Application
Spring-Boot-Classes: BOOT-INF/classes/
Spring-Boot-Lib: BOOT-INF/lib/
Created-By: Apache Maven 3.3.9
Build-Jdk: 1.8.0_171
MANIFEST.MF相关文件为往上短信，不错知道两只要点短信Main-Class和Start-Class。我需要进那步，系统的启用出入口并非是我SpringBoot中确定的main，反而是JarLauncher#main，而再在当中灵活运用射线启用定位好的Start-Class的main策略
java.util.jar.JarFile JDK用具类提供数据的识别jar程序
org.springframework.boot.loader.jar.JarFileSpringboot-loader 分家析产JDK出具JarFile类
java.util.jar.JarEntryDK工具软件类能提供的jar文件下载条款
org.springframework.boot.loader.jar.JarEntry Springboot-loader 遗产继承JDK具备JarEntry类
org.springframework.boot.loader.archive.Archive Springboot抽像起来的保持一致访问共享資源的层
JarFileArchivejar包程序的具象ExplodedArchive文件目次目次JarFile的的作用，一个JarFileArchive就会相对应一名JarFile。在塑造的之时 会辨析内控结构的，去得到 jar包内的其他资料或资料夹类。让我们需要看两下纯虚函数的批注。
/* Extended variant of {@link java.util.jar.JarFile} that behaves in the same way but
* offers the following additional functionality.
* <ul>
* <li>A nested {@link JarFile} can be {@link #getNestedJarFile(ZipEntry) obtained} based
* on any directory entry.</li>
* <li>A nested {@link JarFile} can be {@link #getNestedJarFile(ZipEntry) obtained} for
* embedded JAR files (as long as their entry is not compressed).</li>
</ul>
**/
最基础框架：Bootstrap ClassLoader（载入JDK的/lib子目录下的类）
次的基础：Extension ClassLoader（初始化JDK的/lib/ext总目录下的类）
普通级：Application ClassLoader（小程序她classpath下的类）
ClassLoader添加，就可以让领导的ClassLoader跳转，那样是是为了区域错误代码的运用了非JDK下可类名类似的类。LaunchedURLClassLoader，纯虚函数继续了java.net.URLClassLoader,重写了java.lang.ClassLoader#loadClass(java.lang.String, boolean)，第三我们都再浅论他是如何快速改造双亲协助共识机制。LaunchedURLClassLoader的塑造的办法。
public LaunchedURLClassLoader(URL🅘[] urls,🍌 ClassLoader parent) {
super(urls, parent);
}
the URLs from which to load classes and resources，即fat jar包根据的所有类和网络资源，将该urls参数值交换给父类java.net.URLClassLoader，由父类的java.net.URLClassLoader#findClass程序执行搜寻类具体形式，此种的搜寻来历即搭建具体形式传播融进的urls性能参数。
//LaunchedURLClassLoader的改变
protected Class<?> loadClass(String name, boolean resolve)
throws ClassNotFoundException {
Handler.setUseFastConnectionExceptions(true);
try {
try {
//常试依照类名去表述类所在位置的包，即java.lang.Package，加强组织领导jar in jar里适合的manifest要能和微信相关 //的package微信相关下去
definePackageIfNecessary(name);
}
catch (IllegalArgumentException ex) {
// Tolerate race condition due to being parallel capable
if (getPackage(name) == null) {
// This should never happen as the IllegalArgumentException indicates
// that the package has already been defined and, therefore,
// getPackage(name) should not return null.
//这儿不正确证实，definePackageIfNecessary形式的意义现实的上是再次活性炭过滤掉查询不足的包
throw new AssertionError("Package " + name + " has already been "
+ "defined but it could not be found");
}
}
return super.loadClass(name, resolve);
}
finally {
Handler.setUseFastConnectionExceptions(false);
}
}
super.loadClass(name, resolve)实际情况会换回了java.lang.ClassLoader#loadClass(java.lang.String, boolean)，依据双亲委任共识机制实行快速搜索类，而Bootstrap ClassLoader和Extension ClassLoader都会快速搜索看不到fat jar根据的类，从而还有到Application ClassLoader，赋值java.net.URLClassLoader#findClass
org.springframework.boot.loader.Launcher#launch(java.lang.String[], java.lang.String, java.lang.ClassLoader)反射层跳转逻辑关系更简洁，这就不想阐述，更重点的方面是，在跳转main方式 此前，将在当下线程的下文类访问器设有成LaunchedURLClassLoader
protected void launch(String[] args, String mainClass, ClassLoader classLoader)
throws Exception {
Thread.currentThread().setContextClassLoader(classLoader);
createMainMethodRunner(mainClass, args, classLoader).run();
}
public static void main(String[] args) throws ClassNotFoundEx💎ception, MalformedURLException {
JarFile.registerUrlProtocolHandler();
// 提高LaunchedURLClassLoader类载入器，那里的用到了8个URL，差别应对jar包中依靠包spring-boot-loader和spring-boot，的用到 "!/" 分着，需用org.springframework.boot.loader.jar.Handler净化电脑治疗器净化治疗
LaunchedURLClassLoader classLoader = new LaunchedURLClassLoader(
new URL[] {
new URL("jar:file:/E:/IdeaProjects/oneday-auth/oneday-auth-server/target/oneday-auth-server-1.0.0-SNAPSHOT.jar!/BOOT-INF/lib/spring-boot-loader-1.2.3.RELEASE.jar!/")
, new URL("jar:file:/E:/IdeaProjects/oneday-auth/oneday-auth-server/target/oneday-auth-server-1.0.0-SNAPSHOT.jar!/BOOT-INF/lib/spring-boot-2.1.3.RELEASE.jar!/")
},
Application.class.getClassLoader());
// 刷新类
// 这1个类都在在其次步本地网快速查询中被选出(URLClassLoader的findClass策略)
classLoader.loadClass("org.springframework.boot.loader.JarLauncher");
classLoader.loadClass("org.springframework.boot.SpringApplication");
// 在四步的使用默认值的载入次序在ApplicationClassLoader中被至少找出
classLoader.loadClass("org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration");
// SpringApplication.run(Application.class, args);
}
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-loader</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<version>2.1.3.RELEASE</version>
</dependency>
面对源码研究，在这里的极大获得则都是不能一会儿子去追随弄懂源码中的每一项步码☂的思维，尽管我掌握该策略的的作用。人们可以搞懂的是重要的码，甚至牵涉到的常识点。
我就从Maven的自定议软件逐渐做好追踪定位，随意了对Maven的基础基础信息，在在这个操作过程中几乎理解到JDK对jar的读是有具备分别的手✨段类。还有最重要要的基础基础信息则是自定议类数据加载器。某个源编码下来了并不算说源编码说到底有多完善的，并且想学习他因何而完善的。
