初始SpringBoot：详解特性和结构

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 🔥 推荐专栏：《SSM笔记》《SpringBoot笔记》
         

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目录

前言

一、SpringBoot项目结构

1.启动类的位置

2.pom文件

start

parent

打包

二、依赖管理特性

三、自动配置特性

总结

前言

SpringBoot项目结构，特性介绍（常用到的基本都讲解了，很详细，基于官方文档讲解）。

一、SpringBoot项目结构

IDEA创建非常简单，不是主要讲解，我使用的是IDEA2023.3（这里默认你Maven环境都配好了）

创建完成后的文件结构如下：

• java：java包下存放的是开发创建的类、接口等。
  • 这里restart是我的工程名，同时它就是项目工程文件夹，开发所创建的包、类基本都在这文件夹下。
  • SpringBoot启动类（这里的启动类是RestartApplication，SpringBoot项目创建完成后默认的启动类名称是首字母大写的项目工程名+Application）放在工程文件夹下，即：工程文件夹 / 启动类。不在嵌套文件夹。
• resources
  • 存放静态资源文件的地方：html、css、照片、配置文件（properties文件，yaml文件等）。
• pom.xml
  • 引入依赖文件，用于引入你工程所需要的依赖。

1.启动类的位置

• 官方建议最佳实战就是将启动类放在工程文件夹下的第一层，不需要再嵌套文件夹。
• 官方说：@SpringBootApplication 注解一般都是注解在启动类上的。它默认会扫描当前类下的所有子包（也就是与当前启动类同级文件夹的包及其下的所有包，如下图的customer、order包及其下的所有包）。例如，如果你正在编写一个JPA应用程序，你的 @Entity 类只有定义在启动类的子包下才能被扫描加载到。这样的好处也显而易见，@SpringBootApplication 默认只会扫描加载你项目工程中的组件。

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-java"><span style="color:#708090">//初始创建的SpringBoot项目的启动类都是如下代码：</span>
<span style="color:#0077aa">import</span> org<span style="color:#999999">.</span>springframework<span style="color:#999999">.</span>boot<span style="color:#999999">.</span>SpringApplication<span style="color:#999999">;</span>
<span style="color:#0077aa">import</span> org<span style="color:#999999">.</span>springframework<span style="color:#999999">.</span>boot<span style="color:#999999">.</span>autoconfigure<span style="color:#999999">.</span>SpringBootApplication<span style="color:#999999">;</span>

<span style="color:#999999">@SpringBootApplication</span>
<span style="color:#0077aa">public</span> <span style="color:#0077aa">class</span> RestartApplication <span style="color:#999999">{</span>

	<span style="color:#0077aa">public</span> <span style="color:#0077aa">static</span> <span style="color:#0077aa">void</span> <span style="color:#dd4a68">main</span><span style="color:#999999">(</span>String<span style="color:#999999">[</span><span style="color:#999999">]</span> args<span style="color:#999999">)</span> <span style="color:#999999">{</span>
		SpringApplication<span style="color:#999999">.</span><span style="color:#dd4a68">run</span><span style="color:#999999">(</span>RestartApplication<span style="color:#999999">.</span><span style="color:#0077aa">class</span><span style="color:#999999">,</span> args<span style="color:#999999">)</span><span style="color:#999999">;</span>
	<span style="color:#999999">}</span>

<span style="color:#999999">}</span>
</code></span></span>

2.pom文件

• 大多数Spring Boot应用在POM的 parent 部分使用 spring-boot-starter-parent。 spring-boot-starter-parent 是一个特殊的starter，提供有用的Maven默认值。
• 需要的依赖在 < dependency > 标签内导入需要的< dependeny>

start

• Starter是一系列开箱即用的依赖，你可以在你的应用程序中导入它们。 通过你Starter，可以获得所有你需要的Spring和相关技术的一站式服务，免去了需要到处大量复制粘贴依赖的烦恼。
  • 例如，如果你想开始使用Spring和JPA进行数据库访问，那么可以直接在你的项目中导入 spring-boot-starter-data-jpa 依赖。（也就是说现在你想要什么依赖，只需要spring-boot-start-xxx就可以帮你自动导入这方面的所有常规依赖）
• Starter含了很多你需要的依赖，以使项目快速启动和运行，并拥有一套一致的、受支持的可管理的过渡性依赖。

例子：
在idea的终端输入 mvn dependency:tree打印了一个项目依赖的树状图，如下：

你可以看到 spring-boot-starter-parent 本身没有导入什么依赖（就是一些基本的依赖如spring方面的，日志方面的等）。 要导入必须的依赖，需要编辑 pom.xml 文件。

假如正在开发一个Web应用程序，我们添加一个 spring-boot-starter-web 依赖项：

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-xml"><span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>dependencies</span><span style="color:#999999">></span></span>
    <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>dependency</span><span style="color:#999999">></span></span>
        <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>groupId</span><span style="color:#999999">></span></span>org.springframework.boot<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>groupId</span><span style="color:#999999">></span></span>
        <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>artifactId</span><span style="color:#999999">></span></span>spring-boot-starter-web<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>artifactId</span><span style="color:#999999">></span></span>
    <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>dependency</span><span style="color:#999999">></span></span>
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>dependencies</span><span style="color:#999999">></span></span>
</code></span></span>

如果你再次运行 mvn dependency:tree ，你会看到现在有一些额外的依赖，包括Tomcat web服务器等。基本将常规依赖都引入进来了。

parent

• spring-boot-starter-parent 是一个特殊的starter，它在POM.xml里面声明了spring boot的各个依赖及其版本。子项目直接继承它，子项在导入 spring boot 依赖时，不需要声明版本号。
  • 通俗的说parent部分就是在你导入spring-boot-start–parent时，自动帮你冲裁了版本号，你在dependenys标签里的依赖可以不用写版本号

提问：不想使用仲裁版本怎么办？
在pom.xml重写配置，如下面的代码（这里以mysql为例，换成5.1.43版本）：

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-xml"><span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>properties</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>mysql.version</span><span style="color:#999999">></span></span>5.1.43<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>mysql.version</span><span style="color:#999999">></span></span>
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>properties</span><span style="color:#999999">></span></span>
</code></span></span>

打包

使用Maven快速打包

IDEA内终端运行mvn package

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-java">$ mvn <span style="color:#0077aa">package</span>

<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> Scanning <span style="color:#0077aa">for</span> projects<span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> Building myproject <span style="color:#986801">0.0</span><span style="color:#986801">.1</span><span style="color:#a67f59">-</span><span style="color:#986801">SNAPSHOT</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span> <span style="color:#999999">.</span><span style="color:#999999">.</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">-</span> maven<span style="color:#a67f59">-</span>jar<span style="color:#a67f59">-</span>plugin<span style="color:#a67f59">:</span><span style="color:#986801">2.4</span><span style="color:#a67f59">:</span>jar <span style="color:#999999">(</span><span style="color:#0077aa">default</span><span style="color:#a67f59">-</span>jar<span style="color:#999999">)</span> @ myproject <span style="color:#a67f59">--</span><span style="color:#a67f59">-</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> Building jar<span style="color:#a67f59">:</span> <span style="color:#a67f59">/</span>Users<span style="color:#a67f59">/</span>developer<span style="color:#a67f59">/</span>example<span style="color:#a67f59">/</span>spring<span style="color:#a67f59">-</span>boot<span style="color:#a67f59">-</span>example<span style="color:#a67f59">/</span>target<span style="color:#a67f59">/</span>myproject<span style="color:#a67f59">-</span><span style="color:#986801">0.0</span><span style="color:#986801">.1</span><span style="color:#a67f59">-</span><span style="color:#986801">SNAPSHOT</span><span style="color:#999999">.</span>jar
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">-</span> spring<span style="color:#a67f59">-</span>boot<span style="color:#a67f59">-</span>maven<span style="color:#a67f59">-</span>plugin<span style="color:#a67f59">:</span><span style="color:#986801">3.2</span><span style="color:#986801">.0</span><span style="color:#a67f59">-</span><span style="color:#986801">SNAPSHOT</span><span style="color:#a67f59">:</span>repackage <span style="color:#999999">(</span><span style="color:#0077aa">default</span><span style="color:#999999">)</span> @ myproject <span style="color:#a67f59">--</span><span style="color:#a67f59">-</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#986801">BUILD</span> <span style="color:#986801">SUCCESS</span>
<span style="color:#999999">[</span><span style="color:#986801">INFO</span><span style="color:#999999">]</span> <span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span><span style="color:#a67f59">--</span>

</code></span></span>

另一种：

运行后你会发现工程内多个target文件夹：

如果你查看 target 目录，你应该看到 项目名-0.0.1-SNAPSHOT.jar
（没有target可以在从电脑中找到项目文件夹，里面应该能找到target文件夹，在jar包所在文件夹打开电脑终端，运行java -jar 项目名-1.0-SNAPSHOT.jar）

IDEA终端运行java -jar target/myproject-0.0.1-SNAPSHOT.jar：

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-java">$ java <span style="color:#a67f59">-</span>jar target<span style="color:#a67f59">/</span>myproject<span style="color:#a67f59">-</span><span style="color:#986801">0.0</span><span style="color:#986801">.1</span><span style="color:#a67f59">-</span><span style="color:#986801">SNAPSHOT</span><span style="color:#999999">.</span>jar

  <span style="color:#999999">.</span>   ____          _            __ _ _
 <span style="color:#a67f59">/</span>\\ <span style="color:#a67f59">/</span> ___'_ __ _ <span style="color:#dd4a68">_</span><span style="color:#999999">(</span>_<span style="color:#999999">)</span>_ __  __ _ \ \ \ \
<span style="color:#999999">(</span> <span style="color:#999999">(</span> <span style="color:#999999">)</span>\___ <span style="color:#a67f59">|</span> <span style="color:#50a14f">'_ | '</span>_<span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span> '_ \<span style="color:#a67f59">/</span> _` <span style="color:#a67f59">|</span> \ \ \ \
 \\<span style="color:#a67f59">/</span>  ___<span style="color:#999999">)</span><span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span>_<span style="color:#999999">)</span><span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span> <span style="color:#a67f59">||</span> <span style="color:#999999">(</span>_<span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span>  <span style="color:#999999">)</span> <span style="color:#999999">)</span> <span style="color:#999999">)</span> <span style="color:#999999">)</span>
  '  <span style="color:#a67f59">|</span>____<span style="color:#a67f59">|</span> <span style="color:#999999">.</span>__<span style="color:#a67f59">|</span>_<span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span>_<span style="color:#a67f59">|</span>_<span style="color:#a67f59">|</span> <span style="color:#a67f59">|</span>_\__<span style="color:#999999">,</span> <span style="color:#a67f59">|</span> <span style="color:#a67f59">/</span> <span style="color:#a67f59">/</span> <span style="color:#a67f59">/</span> <span style="color:#a67f59">/</span>
 <span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">=</span><span style="color:#a67f59">|</span>_<span style="color:#a67f59">|=</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">==</span><span style="color:#a67f59">=</span><span style="color:#a67f59">|</span>___<span style="color:#a67f59">/=</span><span style="color:#a67f59">/</span>_<span style="color:#a67f59">/</span>_<span style="color:#a67f59">/</span>_<span style="color:#a67f59">/</span>
 <span style="color:#a67f59">::</span> Spring Boot <span style="color:#a67f59">::</span>  <span style="color:#999999">(</span>v3<span style="color:#999999">.</span><span style="color:#986801">1.2</span><span style="color:#a67f59">-</span><span style="color:#986801">SNAPSHOT</span><span style="color:#999999">)</span>
<span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span>
<span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">(</span>log output here<span style="color:#999999">)</span>
<span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span> <span style="color:#999999">.</span>
<span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span> Started MyApplication in <span style="color:#986801">0.999</span> seconds <span style="color:#999999">(</span>process running <span style="color:#0077aa">for</span> <span style="color:#986801">1.253</span><span style="color:#999999">)</span>

</code></span></span>

要退出应用程序，按 ctrl-c。

如果你想看看这jar里面到底有什么东西，你可以使用 jar tvf：jar tvf target/项目名-0.0.1-SNAPSHOT.jar

二、依赖管理特性

Spring Boot的每个版本都提供了一个它所支持的依赖的列表。 在实践中，你不需要在构建配置中为这些依赖声明版本，因为Spring Boot会帮你管理这些。 当你升级Spring Boot本身时，这些依赖也会一同升级。(所以现在你联系一下parent和start是不是豁然开朗)

• 开发导入starter场景启动器
  1. spring-boot-starter-* ： * 就是某种场景
  2. 只要引入starter，这个场景的所有常规需要的依赖我们都自动引入
  3. 更多SpringBoot所有支持的场景
  4. *-spring-boot-starter： 第三方为我们提供的简化开发的场景启动器。

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-xml">所有场景启动器最底层的依赖
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>dependency</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>groupId</span><span style="color:#999999">></span></span>org.springframework.boot<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>groupId</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>artifactId</span><span style="color:#999999">></span></span>spring-boot-starter<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>artifactId</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>version</span><span style="color:#999999">></span></span>3.1.2<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>version</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>scope</span><span style="color:#999999">></span></span>compile<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>scope</span><span style="color:#999999">></span></span>
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>dependency</span><span style="color:#999999">></span></span>
</code></span></span>

• 无需关注版本号，自动版本仲裁

  1. 引入依赖默认都可以不写版本
  2. 引入非版本仲裁的jar，要写版本号。

• 可以修改默认版本号

  1. 查看spring-boot-dependencies里面规定当前依赖的版本 用的 key。
  2. 在当前项目里面重写配置，如下面的代码。

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-xml"><span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>properties</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>mysql.version</span><span style="color:#999999">></span></span>5.1.43<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>mysql.version</span><span style="color:#999999">></span></span>
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>properties</span><span style="color:#999999">></span></span>
</code></span></span>

IDEA快捷键：

• ctrl + shift + alt + U：以图的方式显示项目中依赖之间的关系。
• alt + ins：相当于Eclipse的 Ctrl + N，创建新类，新包等。

三、自动配置特性

• 自动配好Tomcat
  • 引入Tomcat依赖。
  • 配置Tomcat

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-xml"><span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>dependency</span><span style="color:#999999">></span></span>
	<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>groupId</span><span style="color:#999999">></span></span>org.springframework.boot<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>groupId</span><span style="color:#999999">></span></span>
    <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>artifactId</span><span style="color:#999999">></span></span>spring-boot-starter-tomcat<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>artifactId</span><span style="color:#999999">></span></span>
    <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>version</span><span style="color:#999999">></span></span>3.1.2<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>version</span><span style="color:#999999">></span></span>
    <span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"><</span>scope</span><span style="color:#999999">></span></span>compile<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>scope</span><span style="color:#999999">></span></span>
<span style="color:#e45649"><span style="color:#e45649"><span style="color:#999999"></</span>dependency</span><span style="color:#999999">></span></span>
</code></span></span>

• 自动配好SpringMVC

  • 引入SpringMVC全套组件
  • 自动配好SpringMVC常用组件（功能）

• 自动配好Web常见功能，如：字符编码问题

  • SpringBoot帮我们配置好了所有web开发的常见场景

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-java"><span style="color:#0077aa">public</span> <span style="color:#0077aa">static</span> <span style="color:#0077aa">void</span> <span style="color:#dd4a68">main</span><span style="color:#999999">(</span>String<span style="color:#999999">[</span><span style="color:#999999">]</span> args<span style="color:#999999">)</span> <span style="color:#999999">{</span>
    <span style="color:#708090">//1、返回我们IOC容器</span>
    ConfigurableApplicationContext run <span style="color:#a67f59">=</span> SpringApplication<span style="color:#999999">.</span><span style="color:#dd4a68">run</span><span style="color:#999999">(</span>MainApplication<span style="color:#999999">.</span><span style="color:#0077aa">class</span><span style="color:#999999">,</span> args<span style="color:#999999">)</span><span style="color:#999999">;</span>

    <span style="color:#708090">//2、查看容器里面的组件</span>
    String<span style="color:#999999">[</span><span style="color:#999999">]</span> names <span style="color:#a67f59">=</span> run<span style="color:#999999">.</span><span style="color:#dd4a68">getBeanDefinitionNames</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#0077aa">for</span> <span style="color:#999999">(</span>String name <span style="color:#a67f59">:</span> names<span style="color:#999999">)</span> <span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#dd4a68">println</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span></span>

这里截取了一部分，可以看出里面SpringBoot真的很强大，不需要SSM一样导入一堆依赖。

• 默认的包结构
  • 主程序所在包及其下面的所有子包里面的组件都会被默认扫描进来
  • 无需以前的包扫描配置
  • 想要改变扫描路径
    • @SpringBootApplication(scanBasePackages=“com.dragon”)
    • @ComponentScan 指定扫描路径

<span style="color:#000000"><span style="background-color:#fafafa"><code class="language-java"><span style="color:#999999">@SpringBootApplication</span>
等同于
<span style="color:#999999">@SpringBootConfiguration</span>
<span style="color:#999999">@EnableAutoConfiguration</span>
<span style="color:#999999">@ComponentScan</span><span style="color:#999999">(</span><span style="color:#50a14f">"com.lun"</span><span style="color:#999999">)</span>
</code></span></span>

• 各种配置拥有默认值

  • 默认配置最终都是映射到某个类上，如：MultipartProperties
  • 配置文件的值最终会绑定每个类上，这个类会在容器中创建对象

• 按需加载所有自动配置项

  • 非常多的starter
  • 引入了哪些场景这个场景的自动配置才会开启
  • SpringBoot所有的自动配置功能都在 spring-boot-autoconfigure 包里面
    
    

下面是参考文档，有兴趣的朋友可以看看：

Spring Boot Maven 插件文档
中文文档——SpringBoot入门

总结

以上就是SpringBoot的特性及结构的具体讲解。