Springboot自定义Starter

Starter的工作原理：

       1、Spring Boot在启动时扫描项目所依赖的jar包，寻找包含spring.factories文件的jar包。

       2、读取spring.factories文件获取配置的自动配置类XXXAutoConfiguration。

       3、将自动配置类下满足条件(@ConditionalOnXxx)的Bean加入到IOC容器中

 

编写pom.xml文件：

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.seasy</groupId>
  <artifactId>seasy-spring-boot-starter</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <parent>
  	<groupId>org.springframework.boot</groupId>
  	<artifactId>spring-boot-starter-parent</artifactId>
  	<version>2.0.7.RELEASE</version>
  	<relativePath/>
  </parent>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
  </properties>

  <dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-configuration-processor</artifactId>
        <optional>true</optional>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-autoconfigure</artifactId>
    </dependency>
  </dependencies>
</project>

 

创建核心服务类：

public class SeasyService {
	private SeasyProperties seasyProperties;
	
	public SeasyService(SeasyProperties seasyProperties){
		this.seasyProperties = seasyProperties;
	}
	
	public String login(){
		System.out.println("username=" + seasyProperties.getUsername() + ", password=" + seasyProperties.getPassword());
		return "success";
	}
}

 

创建配置类：

/**
 * 配置类
 * 		只配置@ConfigurationProperties注解，在IOC容器中是获取不到properties配置文件转化的bean。
 * 		可以使用@Component来标注，也可以使@EnableConfigurationProperties(SeasyProperties.class)启用指定的属性类
 * 
 * 属性名对应到application.properties文件的参数，比如seasy.login.username
 */
@ConfigurationProperties("seasy.login") //参数前缀
public class SeasyProperties {
	private String username;
	private String password;
	
	public String getUsername() {
		return username;
	}
	
	public void setUsername(String username) {
		this.username = username;
	}
	
	public String getPassword() {
		return password;
	}
	
	public void setPassword(String password) {
		this.password = password;
	}
}

 

创建自动配置类：

@Configuration

//使配置类生效：将配置文件中对应的值和配置类绑定起来，并把配置类加入到IOC容器中
@EnableConfigurationProperties(SeasyProperties.class)

//存在SeasyService类自动配置才生效
@ConditionalOnClass(SeasyService.class)

//只有配置了属性seasy.login.enabled=true，才加载和自动配置
@ConditionalOnProperty(prefix="seasy.login", value="enabled", havingValue="true") //必须设置为true
//@ConditionalOnProperty(prefix="seasy.login", value="enabled", matchIfMissing=true) //没有设置则默认为true

public class SeasyAutoConfiguration {
	@Autowired
	private SeasyProperties seasyProperties;
	
	@Bean
	//Spring容器不存在该Bean时才实例Bean
	@ConditionalOnMissingBean
	public SeasyService getSeasyService(){
		return new SeasyService(seasyProperties);
	}
}

 

在 src\main\resources\META-INF 目录下新建spring.factories文件，添加内容如下：

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.seasy.SeasyAutoConfiguration

 

 执行 mvn clean install 命令编译打包工程到本地maven仓库中。

 

测试：

      在测试工程引入依赖包：

<dependency>
        <groupId>com.seasy</groupId>
  		<artifactId>seasy-spring-boot-starter</artifactId>
  		<version>0.0.1-SNAPSHOT</version>
    </dependency>

 

     在application.properties文件添加配置信息：

seasy.login.enabled=true
seasy.login.username=dev
seasy.login.password=123

 

     在Controller类引用服务类，并调用提供的方法：

@Autowired
private SeasyService seasyService;

@RequestMapping("/index")
public String index(){
	String result = seasyService.login();
	System.out.println(result);
	
	return "index";
}