SpringBoot 自定义Starter
手写Starter
创建项目
创建一个Maven项目，或者通过Spring Initializr创建一个Spring Boot项目，添加Maven依赖：
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 https://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>2.4.1</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.shiguangping</groupId>
<artifactId>simple-spring-boot-starter</artifactId>
<version>1.0.0</version>
<name>simple-spring-boot-starter</name>
<description>手写一个starter演示</description>
<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>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-autoconfigure</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<skip>true</skip>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>
</project>
Starter 命名规范：
Spring官方Starter命名通常为：
spring-boot-starter-{name}Spring官方建议非官方的Starter命名遵循：
{name}-spring-boot-starter格式
编写Service
service中写了一个拼接字符串的方法，定义了前缀和后缀两个成员变量，方法返回拼接后的字符串。
ExampleService.java
package com.shiguangping.service;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
/**
* 示例Service
*
* @author liyan
* @since 2021.1.13
*/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class ExampleService {
private String prefix;
private String suffix;
/**
* 拼装字符串
*
* @param word
* @return
*/
public String wrap(String word) {
return prefix + word + suffix;
}
}
编写属性类
ExampleServiceProperties.java
package com.shiguangping.configure;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
/**
* 属性
*
* @author liyan
* @since 2021.1.13
*/
@Data
@ConfigurationProperties(prefix = "example.service")
public class ExampleServiceProperties {
private String prefix;
private String suffix;
}
编写自动配置类
ExampleAutoConfigure.java
package com.shiguangping.configure;
import com.shiguangping.service.ExampleService;
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;
/**
* 自动配置类
*
* @author liyan
* @since 2021.1.13
*/
@Configuration
@ConditionalOnClass(ExampleService.class)
@EnableConfigurationProperties(ExampleServiceProperties.class)
public class ExampleAutoConfigure {
@Autowired
private ExampleServiceProperties properties;
@Bean
@ConditionalOnMissingBean
@ConditionalOnProperty(prefix = "example.service", value = "enabled", havingValue = "true")
ExampleService exampleService() {
return new ExampleService(properties.getPrefix(), properties.getSuffix());
}
}
添加spring.factories
在resources/META-INF/下创建spring.factories文件：
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.shiguangping.configure.ExampleAutoConfigure
如果有多个自动配置类，用逗号分隔换行。Spring Boot会最先到META-INF下寻找自动配置类。
打包
终端运行mvn install命令，将项目打包并发布到本地的Maven仓库。
如果是Spring Boot项目，需要在插件配置中添加skip标签：
pom.xml
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<skip>true</skip>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
测试
新建一个Spring Boot项目，引入Maven依赖：
<dependency>
<groupId>com.shiguangping</groupId>
<artifactId>simple-spring-boot-starter</artifactId>
<version>1.0.0</version>
</dependency>
修改配置文件application.yml，添加如下内容：
example:
service:
enabled: true
suffix: Nice
prefix: Hello
编写测试类：
package com.example.demo.simple;
import com.shiguangping.service.ExampleService;
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;
@SpringBootTest
@RunWith(SpringRunner.class)
public class SimpleTest {
@Autowired
private ExampleService exampleService;
@Test
public void test(){
String s = exampleService.wrap("Java");
System.out.println(s);
}
}
运行结果：
HelloJavaNice
手写Starter引用成功~
总结
- Spring Boot启动时会先扫描引入的所有依赖，寻找带有
spring.factories文件的Jar包； - 根据
spring.factories文件加载AutoConfigure类； - 根据自动配置类中
@Conditional注解的条件，进行自动配置，并将Bean注册到Spring容器当中。