SpringBoot自动配置自定义Starter

落日映苍穹つ 2022-02-24 09:06 339阅读 0赞

下面创建一个 spring-boot-starter-hello 的启动器，这个启动器的Person与配置文件的属性绑定，可以供引入这个启动器的项目进行配置。HelloService 使用sayHello方法输出Person内容。HelloAautoConfiguration是配置类，产生HelloService的bean。

项目结构：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpYW5nd2VubWFpbA_size_16_color_FFFFFF_t_70][]

首先创建一个SpringBoot项目，pom要做一些修改：

添加如下两个依赖：

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

spring-boot-starter：包含自动配置的基本包，spring-boot-configuration-processor：添加这个依赖会在配置文件产生提示。

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>
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>1.5.19.RELEASE</version>
    		<relativePath/> 
    	</parent>
    
    	<groupId>cn.cld</groupId>
    	<artifactId>spring-boot-starter-hello</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    
    	<properties>
    		<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-configuration-processor</artifactId>
    			<optional>true</optional>
    		</dependency>
    
    	</dependencies>
    
    </project>

Person.java

package cn.cld;
    
    import org.springframework.boot.context.properties.ConfigurationProperties;
    
    @ConfigurationProperties(prefix = "person")
    public class Person {
        private String id="DEFAULT";
        private String name="DEFAULT1";
    
        public String getId() {
            return id;
        }
    
        public void setId(String id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public String toString() {
            return "Person{" +
                    "id='" + id + '\'' +
                    ", name='" + name + '\'' +
                    '}';
        }
    }

@ConfigurationProperties(prefix = "person") 把Person类和配置文件绑定。

HelloService.java

package cn.cld;
    
    public class HelloService {
        private Person person;
    
        public Person getPerson() {
            return person;
        }
    
        public void setPerson(Person person) {
            this.person = person;
        }
    
        public String sayHello(){
            return "Say : "+this.person;
        }
    }

HelloAautoConfiguration.java

package cn.cld;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
    import org.springframework.boot.context.properties.EnableConfigurationProperties;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    @EnableConfigurationProperties(Person.class)
    @ConditionalOnWebApplication
    @ConditionalOnClass(HelloService.class)
    @ConditionalOnProperty(prefix = "person",value = {"id","name"},matchIfMissing=true)
    public class HelloAautoConfiguration {
        @Autowired
        private Person person;
    
        @Bean
        @ConditionalOnMissingBean(HelloService.class)
        public HelloService helloService(){
            HelloService hs=new HelloService();
            hs.setPerson(person);
            return hs;
        }
    
        public int getOrder(){
            return 0;
        }
    }

@EnableConfigurationProperties(Person.class) 把与配置文件绑定的Person类导入到容器；

@ConditionalOnWebApplication 只有WEB应用，该配置类才生效；

@ConditionalOnClass(HelloService.class) 只有存在HelloService这个类配置类才生效；

@ConditionalOnProperty(prefix = "person",value = {"id","name"},matchIfMissing=true) 配置中存在person前缀，名称有id有name时候才生效，true说明即使不存在也生效，false不存在报错。

@ConditionalOnMissingBean(HelloService.class)容器里不存在HelloService的bean时候才创建该Bean.

最后：如果这个模块无法被其他模块引用，需要在pom修改

<build>
       <plugins>
          <plugin>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-maven-plugin</artifactId>
             <configuration>
                <skip>true</skip>
             </configuration>
          </plugin>
       </plugins>
    </build>

最后创建META-INF目录在里面创建如下文件

spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=cn.cld.HelloAautoConfiguration

最后，其他SpringBoot项目引入这个自定义启动器，就可以注入HelloService进行sayHello调用，并可以在配置文件里配置person的值。

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