SpringBoot自定义Starter

背景

在做SpringBoot开发时，各种starter （场景启动器） 必不可少，它们就像可插拔式的插件，只要在pom文件中引用 springboot 提供的场景启动器， 再进行少量的配置就可以使用相应的功能，但SpringBoot并不能囊括我们的所有使用场景，这时候就需要我们自定义starter来实现定制化功能。

Spring Boot Starter工作原理

• 1.SpringBoot在启动的时候会扫描项目所依赖的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AutoConfiguration
• 3.将自动配置类下满足条件(@ConditionalOnXxx)的@Bean放入到Spring容器中(Spring Context)

自定义starter

1.创建一个maven工程

pom文件

<?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>2.2.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

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

    <name>hello-spring-boot-starter</name>

    <properties>
        <java.version>1.8</java.version>
    </properties>

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

</project>

2.Proprerty类

创建类PersonProperties

@ConfigurationProperties注解的作用是告诉SpringBoot将本类中的所有属性和配置文件中相关的配置进行绑定，prefix 指定配置文件里的前缀，配置了这个注解后会根据配置文件的所有属性进行一一映射

package com.matins.starter.property;


import org.springframework.boot.context.properties.ConfigurationProperties;

/**
 * @Description:
 * @author: wei.wang
 * @since: 2019/12/18 23:46
 * @history: 1.2019/12/18 created by wei.wang
 */
@ConfigurationProperties(prefix = "spring.person")
public class PersonProperties {
    // 姓名
    private String name;
    // 年龄
    private int age;
    // 性别
    private String sex = "M";

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "PersonProperties{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }
}

3.Service类

接口PersonService

package com.matins.starter.service;

/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/6/24 16:37
 * @history: 1.2020/6/24 created by wei.wang
 */
public interface PersonService {

    void hello();
}

类PersonServiceImpl

package com.matins.starter.service.impl;

import com.matins.starter.service.PersonService;

/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/6/24 16:38
 * @history: 1.2020/6/24 created by wei.wang
 */
public class PersonServiceImpl implements PersonService {

    // 姓名
    private String name;
    // 年龄
    private int age;
    // 性别
    private String sex = "M";

    public PersonServiceImpl(String name, int age, String sex) {
        this.name = name;
        this.age = age;
        this.sex = sex;
    }

    @Override
    public void hello() {
        System.out.println(String.format("Hello from the default starter , name %s, age %s, sec %s", name, age, sex));
    }
}

4.自动配置类

@Configuration //指定这个类是一个配置类
@ConditionalOnXXX //指定条件成立的情况下自动配置类生效
@AutoConfigureOrder //指定自动配置类的顺序
@Bean //向容器中添加组件
@ConfigurationProperties //结合相关xxxProperties来绑定相关的配置
@EnableConfigurationProperties //让xxxProperties生效加入到容器中
@ConditionalOnClass：当类路径classpath下有指定的类的情况下进行自动配置
@ConditionalOnMissingBean:当容器(Spring Context)中没有指定Bean的情况下进行自动配置
@ConditionalOnProperty(prefix = “example.service”,name = "auth", value = “enabled”, matchIfMissing = true)，当配置文件中example.service.auth.enabled=true时进行自动配置，如果没有设置此值就默认使用matchIfMissing对应的值
@ConditionalOnMissingBean，当Spring Context中不存在该Bean时。
@ConditionalOnBean:当容器(Spring Context)中有指定的Bean的条件下
@ConditionalOnMissingClass:当类路径下没有指定的类的条件下
@ConditionalOnExpression:基于SpEL表达式作为判断条件
@ConditionalOnJava:基于JVM版本作为判断条件
@ConditionalOnJndi:在JNDI存在的条件下查找指定的位置
@ConditionalOnNotWebApplication:当前项目不是Web项目的条件下
@ConditionalOnWebApplication:当前项目是Web项目的条件下
@ConditionalOnResource:类路径下是否有指定的资源
@ConditionalOnSingleCandidate:当指定的Bean在容器中只有一个，或者在有多个Bean的情况下，用来指定首选的Bean

自动配置类PersonServiceAutoConfiguration

package com.matins.starter.configuration;

import com.matins.starter.property.PersonProperties;
import com.matins.starter.service.PersonService;
import com.matins.starter.service.impl.PersonServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;


/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/6/24 16:38
 * @history: 1.2020/6/24 created by wei.wang
 */
@Configuration
@EnableConfigurationProperties(PersonProperties.class)
@ConditionalOnClass(PersonService.class)
public class PersonServiceAutoConfiguration {

    @Autowired
    private PersonProperties properties;

    @Bean(name = "person")
    public PersonService helloService() {
        return new PersonServiceImpl(properties.getName(), properties.getAge(), properties.getSex());
    }
}

5.配置文件

在resources/META-INF/下创建文件spring.factories，SpringBoot在启动的时候会扫描项目所依赖的JAR包，寻找包含spring.factories文件的JAR包，读取spring.factories文件获取配置的自动配置类AutoConfiguration，然后将自动配置类下满足条件(@ConditionalOnXxx)的@Bean放入到Spring容器中(Spring Context)，这样使用者就可以直接用来注入，因为该类已经在容器中了

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.matins.starter.configuration.PersonServiceAutoConfiguration

6.测试

新建一个SpringBoot项目，将Starter工程打包并引入

添加本地jar包到Maven

以管理员身份运行CMD

mvn install:install-file -Dfile="F:\GitCode\zero\hello-spring-boot-starter\target\hello-spring-boot-starter-1.0-SNAPSHOT.jar" -DgroupId=com.matins.starter -DartifactId=hello-spring-boot-starter -Dversion=0.0.1-SNAPSHOT -Dpackaging=jar

然后在Maven中引用

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

配置文件

在application.properties中添加，PersonProperties中使用了 @ConfigurationProperties(prefix = "spring.person")，prefix 指定配置文件里的前缀，会根据配置的信息将属性一一映射

spring.person.age=23
spring.person.name=ss
spring.person.sex=F

测试方法

可以直接@Autowired自动注入，或者使用getBean的方法获取bean

package com.zero.auth.controller;


import com.matins.starter.property.PersonProperties;
import com.matins.starter.service.PersonService;
import com.zero.auth.config.SpringUtil;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

/**
 * @Description:
 * @author: wei.wang
 * @since: 2019/12/19 0:34
 * @history: 1.2019/12/19 created by wei.wang
 * <p>
 * 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，
 * 然后读取spring.factories文件获取配置的自动配置类AutoConfiguration，
 * 然后将自动配置类下满足条件(@ConditionalOnXxx)的@Bean放入到Spring容器中(Spring Context)
 * 这样使用者就可以直接用来注入，因为该类已经在容器中了
 */
@RunWith(SpringRunner.class)
@SpringBootTest
public class TestControllerTest {

    @Autowired
    PersonService personService1;

    @Autowired
    private PersonProperties properties;


    @Test
    public void auth() {
        PersonService personService = (PersonService) SpringUtil.getBean("person");
        personService.hello();
        personService1.hello();
    }
}

SpringUtil

package com.zero.auth.config;


import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/6/25 16:56
 * @history: 1.2020/6/25 created by wei.wang
 */
@Component
public class SpringUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContextParam) throws BeansException {
        applicationContext = applicationContextParam;
    }

    public static Object getObject(String id) {
        Object object = null;
        object = applicationContext.getBean(id);
        return object;
    }

    public static <T> T getObject(Class<T> tClass) {
        return applicationContext.getBean(tClass);
    }

    public static Object getBean(String tClass) {
        return applicationContext.getBean(tClass);
    }

    public <T> T getBean(Class<T> tClass) {
        return applicationContext.getBean(tClass);
    }
}

测试结果

Hello from the default starter , name ss, age 23, sec F
Hello from the default starter , name ss, age 23, sec F