自定义SpringBoot stater

stater的启动原理

  • stater-pom引入autoconfigure包

  • autoconfigure包中的配置使用META-INFO/spring.factories中的“org.springframework.boot.autoconfigure.EnableAutoConfiguration”的值，使得项目启动时加载指定的自动配置类

    这里的autoconfigure指的是我们通过can-spring-boot-stater依赖的can-spring-boot-stater-autoconfigureimage-20230505232632078

自定义的stater步骤

1.创建can-spring-boot-stater删除多余的配置和文件夹，目录如下：

image-20230505232804400

pom文件引入can-spring-boot-stater-autoconfigure的坐标

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<dependency>
  <groupId>com.can</groupId>
  <artifactId>can-spring-boot-stater-autoconfigure</artifactId>
  <version>0.0.1-SNAPSHOT</version>
</dependency>

2.使用spring initializr创建can-spring-boot-stater-autoconfigure，选择Spring web和Spring Configuration Processor

pml文件如下

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.7.11</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.can</groupId>
	<artifactId>can-spring-boot-stater-autoconfigure</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>can-spring-boot-stater-autoconfigure</name>
	<description>can-spring-boot-stater-autoconfigure</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

    <!-- 自定义配置提示坐标 -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<version>2.3.4.RELEASE</version>
			<optional>true</optional>
		</dependency>
	</dependencies>


</project>

3.创建CanProperties.class

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@ConfigurationProperties(prefix = "can")
public class CanProperties {

    private String prefix;

    private String suffix;

    public String getPrefix() {
        return prefix;
    }

    public void setPrefix(String prefix) {
        this.prefix = prefix;
    }

    public String getSuffix() {
        return suffix;
    }

    public void setSuffix(String suffix) {
        this.suffix = suffix;
    }
}

4.定义业务类CanService

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public class CanService {

    private CanProperties canProperties;

    public CanProperties getCanProperties() {
        return canProperties;
    }

    public void setCanProperties(CanProperties canProperties) {
        this.canProperties = canProperties;
    }

    public String sayHello(String name){
        return canProperties.getPrefix()+"--"+name+"--"+canProperties.getSuffix();
    }
}

5.创建自动配置类并添加到IOC中

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@Configuration // 添加到IOC容器
@ConditionalOnWebApplication // web 应用才生效
@EnableConfigurationProperties(CanProperties.class) // 让属性文件生效
public class CanAutoConfiguration {

    @Autowired
    private CanProperties canProperties;

    @Bean // 注入到容器中
    @ConditionalOnMissingBean(CanService.class)
    public CanService canService(){
        CanService canService = new CanService();
        canService.setCanProperties(canProperties);
        return canService;
    }
}

6.在resource目录下创建META-INF/spring.factories文件

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# AutoConfigure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
  com.can.autoconfigure.CanAutoConfiguration

7.clean can-spring-boot-stater-autoconfigure 项目，然后install ，can-spring-boot-stater-autoconfigure重复这个步骤

8.新建一个demo，引入自定义stater坐标，并设置属性

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<!--    自定义stater坐标   -->
        <dependency>
            <groupId>com.can</groupId>
            <artifactId>can-spring-boot-stater</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
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can.prefix=nihao
can.suffix=fitting

image-20230505235159372

总结：

我们在测试Controller中使用了@Autowired去自动导入了我们在hello-spring-boot-starter-autoconfigure定义的业务类，在自动导入之前，springboot就已经扫描完所有导入starter的类，最终会扫描到每个starter类依赖的xxxAutoConfigure下的META-INF/spring.factories，通过该文件获取到xxxAutoConfiguration的全类限定名，就会去加载我们写在xxx-spring-boot-xxxAutoConfigure项目下的xxxAutoConfiguration类，也就是我们前面定义的CanAutoConfiguration，通过判断是否执行创建CanService，从而决定是否对CanProperties.class进行下一步操作（开启与对应properties的前缀进行绑定以及添加到IOC容器）

在HelloServiceAutoConfiguration中使用**@ConditionalOnMissingBean(CanService.class)，如果我们在当前容器中也就是测试项目容器有CanService.class的存在，也就不会去执行CanServiceAutoConfiguration**下的某个对应方法