自定义自动配置

所谓自动配置，就是没有显示声明扫描或者配置一个Bean，但是当某些条件触发后，这些Bean就会被纳入Spring管理，并且能够对这些Bean进行一些初始化配置（主要通过配置文件）

需求：只要存在HelloService，就自动配置这个Bean

pom

<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.wisely</groupId>
    <artifactId>spring-boot-starter-hello</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-boot-starter-hello</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
            <version>1.5.1.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>




自动配置类

package com.wisely;

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.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * Created by sherry on 17/2/16.
 */
@Configuration
@ConditionalOnClass(HelloService.class)
@ConditionalOnProperty(prefix = "hello",value = "enabled",matchIfMissing = true)
public class HelloServiceAutoConfiguration {

    @Autowired
    private HelloServiceYml helloServiceYml;

    @Bean
    @ConditionalOnMissingBean(HelloService.class)
    public HelloService helloService(){
        HelloService helloService = new HelloService();
        helloService.setMsg(helloServiceYml.getMsg());
        return helloService;
    }

}


将这个jar发布后，只要引入这个jar，并且项目中存在HelloService类，不需要配置，就会被Spring管理