SpringBoot（24） - 创建自定义stater（2） - demo

绝地灬酷狼 2022-04-18 04:58 220阅读 0赞

参考：[https://docs.spring.io/spring-boot/docs/1.5.17.RELEASE/reference/htmlsingle/\#boot-features-developing-auto-configuration][https_docs.spring.io_spring-boot_docs_1.5.17.RELEASE_reference_htmlsingle_boot-features-developing-auto-configuration]

[https://www.cnblogs.com/cz-xjw/p/6632402.html][https_www.cnblogs.com_cz-xjw_p_6632402.html]

计划实现这样一个需求，只有明确说明不自动配置时，则不配置。当自动配置生效时，读取指定的属性；若没有配置，默认值是空字符串。

1. 自定义starter

（1）pom.xml

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.momo.springboot-starter</groupId>
        <artifactId>hello-spring-boot-starter</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <packaging>jar</packaging>
        <name>hello-spring-boot-starter</name>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.5.17.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-starter</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-configuration-processor</artifactId>
                <optional>true</optional>
            </dependency>
        </dependencies>
    
        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>
    </project>

（2）读取配置文件属性

@ConfigurationProperties(prefix = "hello")
    public class HelloProperties {
        
        private boolean enable;
        
        // 默认值""
        private String msg = "";
    
        // getter setter略
    }

（3）处理类

public class HelloHandler {
        
        private String msg;
        
        public String sayHello() {
            return "Hello " + msg;
        }
    
        public void setMsg(String msg) {
            this.msg = msg;
        }
    }

（4）自动配置类

通过条件注解配置自动配置是否生效

@Configuration
    // 启用对指定带@ConfigurationProperties注解的bean的支持
    @EnableConfigurationProperties(value = HelloProperties.class)
    // classpath路径下存在HelloHandler类则配置
    @ConditionalOnClass(HelloHandler.class)
    // 配置文件hello.enable=true则配置，如果没有该属性则默认设置为true
    @ConditionalOnProperty(prefix = "hello", name = "enable", matchIfMissing = true)
    public class HelloAutoConfiguration {
        
        @Autowired
        private HelloProperties helloProperties;
        
        @Bean
        @ConditionalOnMissingBean(HelloHandler.class)
        public HelloHandler helloHandler() {
            HelloHandler helloHandler = new HelloHandler();
            helloHandler.setMsg(helloProperties.getMsg());
            return helloHandler;
        }
    }

（5）spring.factories

src/main/resouces添加 META-INF/spring.factories，同时配置需要自动配置的类：

# Auto Configure
    org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
    com.momo.springbootstarter.hello.HelloAutoConfiguration

2. 测试自动配置

（1）添加自定义的starter

<dependency>
        <groupId>com.momo.springboot-starter</groupId>
    	<artifactId>hello-spring-boot-starter</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </dependency>

（2）application.yml

hello: 
      enable: true
      msg: momo

（3）测试

当hello.enable=true或不存在该属性时，将会自动注入HelloHandler；hello.enable=false则不会注入

自动注入时，将获取hello.msg属性值，若没有配置则默认为空字符串

@RestController
    public class HelloController {
        
        @Autowired(required = false)
        private HelloHandler helloHandler;
        
        @GetMapping("/sayHello")
        public String sayHello() {
            return helloHandler == null ? "null" : helloHandler.sayHello();
        }
    }

demo代码：[https://github.com/mytt-10566/springboot-starter][https_github.com_mytt-10566_springboot-starter]

[https_docs.spring.io_spring-boot_docs_1.5.17.RELEASE_reference_htmlsingle_boot-features-developing-auto-configuration]: https://docs.spring.io/spring-boot/docs/1.5.17.RELEASE/reference/htmlsingle/#boot-features-developing-auto-configuration
[https_www.cnblogs.com_cz-xjw_p_6632402.html]: https://www.cnblogs.com/cz-xjw/p/6632402.html
[https_github.com_mytt-10566_springboot-starter]: https://github.com/mytt-10566/springboot-starter