2、SpringBoot_依赖介绍

三、SpringBoot介绍

1.parent

前言：之前是使用spring/springmvc 开发，整合不同的组件会有很多依赖，这些依赖会涉及到很多的版本信息，版本信息多了之后可能会导致版本冲突问题
概述：把很多组件技术的搭配放到一起，名字就叫 parent

1.1实际开发中会引入 parent

引入parent

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.7.5</version><relativePath/> <!-- lookup parent from repository -->
</parent>

点击后发现又引入了一个 parent

通过该parent 能够找到对应的搭配

<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>2.7.5</version>
</parent>

通过propertie管理版本信息

<properties><activemq.version>5.16.5</activemq.version><antlr2.version>2.7.7</antlr2.version><appengine-sdk.version>1.9.98</appengine-sdk.version><artemis.version>2.19.1</artemis.version><aspectj.version>1.9.7</aspectj.version><assertj.version>3.22.0</assertj.version><atomikos.version>4.0.6</atomikos.version><awaitility.version>4.2.0</awaitility.version><build-helper-maven-plugin.version>3.3.0</build-helper-maven-plugin.version><byte-buddy.version>1.12.18</byte-buddy.version><cache2k.version>2.6.1.Final</cache2k.version>
</properties>

通过dependencyManagement去管理依赖，子模块想要使用需要去引用依赖才可以，该标签不强制使用依赖需要时才导入

<dependencyManagement><dependencies><dependency><groupId>org.apache.activemq</groupId><artifactId>activemq-amqp</artifactId><version>${activemq.version}</version></dependency><dependency><groupId>org.apache.activemq</groupId><artifactId>activemq-blueprint</artifactId><version>${activemq.version}</version></dependency>
</dependencyManagement>

1.2引入依赖

通过 dependencies

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>
</dependency>

通过导入方式获取依赖（使用alibaba的方式创建的）

<dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>${spring-boot.version}</version><type>pom</type><scope>import</scope></dependency></dependencies>
</dependencyManagement>

2.starter

回顾springmvc
- 问题：之前的操作导入依赖比较麻烦，比如我们要使用Spring-webmvc 一定会去使用Spring-web
- 引入太繁琐不好管理
starter：springboot团队直接把这些固定搭配技术做成一个成品

2.1实际开发体验

开发springmvc（引入此依赖就解决了springmvc的一系列引用，内部引用了多个web开发需要的依赖，就可以直接进行web的开发）
```
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>
</dependency>
```

点击引入的依赖会有如下依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-json</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>5.3.23</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.3.23</version><scope>compile</scope></dependency></dependencies>

如何引入json操作

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-json</artifactId><version>2.7.5</version><scope>compile</scope>
</dependency>

点开又会找到曾经我们导入的依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>5.3.23</version><scope>compile</scope></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.13.4.2</version><scope>compile</scope></dependency><dependency><groupId>com.fasterxml.jackson.datatype</groupId><artifactId>jackson-datatype-jdk8</artifactId><version>2.13.4</version><scope>compile</scope></dependency><dependency><groupId>com.fasterxml.jackson.datatype</groupId><artifactId>jackson-datatype-jsr310</artifactId><version>2.13.4</version><scope>compile</scope></dependency><dependency><groupId>com.fasterxml.jackson.module</groupId><artifactId>jackson-module-parameter-names</artifactId><version>2.13.4</version><scope>compile</scope></dependency>
</dependencies>

2.2starter总结

starter 其实就是很多个坐标的组合
以后引入了什么坐标，直接通过maven观察即可

2.3parent和starter总结

parent作用：
- 定义若干版本信息，交给springboot统一管理，目的是减少依赖冲突
starter作用
- 在同一个坐标中定义多个坐标，目的是简化依赖配置
使用步骤
- 先去找有没有starter ，如果有直接引用
- 没有直接提供版本信息即可

3.引导类

3.1传统spring配置

提供如下配置
- SpringConfig
- SpringMvcConfig

3.2引导类作用

SpringBoot工程提供引导类用来启动程序

SpringBoot工程启动后创建并初始化Spring容器

证明创建了Spring容器

@SpringBootApplication
public class FourSpringbootApplication {public static void main(String[] args) {ConfigurableApplicationContext context = SpringApplication.run(FourSpringbootApplication.class, args);TestController bean = context.getBean(TestController.class);System.out.println(bean.test04());}
}

注意：引导类必须有一个注解@SpringBootApplication，否则启动不起来

4.内嵌tomcat

4.1定义依赖

依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>
</dependency>

点开发现如下依赖

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-json</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><version>2.7.5</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>5.3.23</version><scope>compile</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.3.23</version><scope>compile</scope></dependency></dependencies>

点击spring-boot-starter-tomcat

<dependencies><dependency><groupId>jakarta.annotation</groupId><artifactId>jakarta.annotation-api</artifactId><version>1.3.5</version><scope>compile</scope></dependency><dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-core</artifactId><version>9.0.68</version><scope>compile</scope><exclusions><exclusion><artifactId>tomcat-annotations-api</artifactId><groupId>org.apache.tomcat</groupId></exclusion></exclusions></dependency><dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-el</artifactId><version>9.0.68</version><scope>compile</scope></dependency><dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-websocket</artifactId><version>9.0.68</version><scope>compile</scope><exclusions><exclusion><artifactId>tomcat-annotations-api</artifactId><groupId>org.apache.tomcat</groupId></exclusion></exclusions></dependency></dependencies>

4.2Tomcat运行原理

tomcat:是java语言开发的软件，就可以通过直接创建tomcat对象的方式去运行tomcat

如何交给spring管理的

<dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-core</artifactId><version>9.0.68</version><scope>compile</scope><exclusions><exclusion><artifactId>tomcat-annotations-api</artifactId><groupId>org.apache.tomcat</groupId></exclusion></exclusions>
</dependency>

通过 starter引入 tomcat 服务器之后就可以直接创建tomcat对象了

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId><version>2.7.5</version><scope>compile</scope>
</dependency>

4.3更换内置服务器

tomcat(默认)：apache公司的，受众大，使用多，提供了较多组件
jetty：轻量级服务器，负载比tomcat弱
undertow

更换内置服务器操作

<dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId><exclusions><exclusion><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-tomcat</artifactId></exclusion></exclusions></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jetty</artifactId></dependency></dependencies>