详解SpringBoot如何自定义Starter

目录

• 阅读收获
• 本章源码下载
• 什么是Starter
• 为什么使用Starter
• Springboot自动配置
• spring.factories
• Starter开发常用注解
• Full全模式和Lite轻量级模式
• Starter命名规范
• 开发Starter

• 1. 创建Starter项目
• 2. 添加依赖
• 3. 编写属性类
• 4. 自定义业务类
• 5. 编写自动配置类
• 6. 编写spring.factories
• 7. 编写配置提示文件（非必须）

• 1. 前置环境
• 2. 添加依赖
• 3. 测试类
• 4. 修改配置文件
• 5. 运行程序打印
• 6. 查看自动配置类生效的方法

@Configuration(proxyBeanMethods = false)
public class AppConfig {
    //放一份myBean到ioc容器
    @Bean
    public Mybean myBean() {
        return new Mybean();
    }
    //放一份yourBean到ioc容器
    @Bean
    public YourBean yourBean() {
        System.out.println("==========");
        //注意：@Configuration(proxyBeanMethods = false)：myBean()方法不代理，直接调用
        //注意：@Configuration(proxyBeanMethods = true)：myBean()方法代理，从ioc容器拿
        return new YourBean(myBean());
    }
}

<?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">
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.ljw</groupId>
    <artifactId>ljw-spring-boot-starter</artifactId>
    <version>1.0</version>
   <properties>
        <java.version>1.8</java.version>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <!--        包含自动配置的代码-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-autoconfigure</artifactId>
        </dependency>
        <!--        配置文件点击可以跳转实体-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>
</project>

@ConfigurationProperties(prefix = "ljw.config")
public class HelloProperties {
    private String name = "hello 默认值！";
    private int age = 8;
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

public class HelloService {
    private String name;
    private int age;
    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 hello() {
        return "HelloService{" +
                "name='" + name + ''' +
                ", age=" + age +
                '}';
    }
}

@Configuration(proxyBeanMethods = false)
// 当存在某个类时，此自动配置类才会生效
@ConditionalOnClass(value = {HelloService.class})
// 导入我们自定义的配置类,供当前类使用
@EnableConfigurationProperties(value = HelloProperties.class)
// 只有非web应用程序时此自动配置类才会生效
@ConditionalOnWebApplication
//判断ljw.config.flag的值是否为“true”， matchIfMissing = true：没有该配置属性时也会正常加载
@ConditionalOnProperty(prefix = "ljw.config", name = "flag", havingValue = "true", matchIfMissing = true)
public class HelloAutoConfiguration {
    /**
     * @param helloProperties 直接方法签名入参注入HelloProperties,也可以使用属性注入
     * @return
     */
    @Bean
    @ConditionalOnMissingBean(HelloService.class)
    //@ConditionalOnProperty(prefix = "ljw.config", name = "flag", havingValue = "true", matchIfMissing = true)
    public HelloService helloService(HelloProperties helloProperties) {
        HelloService helloService = new HelloService();
        //把获取的信息注入
        helloService.setName(helloProperties.getName());
        helloService.setAge(helloProperties.getAge());
        return helloService;
    }
}

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.ljw.starter.config.HelloAutoConfiguration

{"properties": [
    {
      "name": "ljw.config.name",
      "type": "java.lang.String",
      "defaultValue": "hello 默认值！这里配置的是提示，真正默认值在Properties里面",
      "description": "这是字符串名称啊."
    },
    {
      "name": "ljw.config.age",
      "defaultValue": 8,
      "description": "这是int类型的年龄啊.",
      "deprecation": {
              "reason": "过时原因.",
              "replacement": "替代key是：ljw.config.age22",
              "level": "warning"
            }
    }
]}

{
  "groups": [
    {
      "name": "ljw.config",
      "type": "com.ljw.starter.properties.HelloProperties",
      "sourceType": "com.ljw.starter.properties.HelloProperties"
    }
  ],
  "properties": [
    {
      "name": "ljw.config.name",
      "type": "java.lang.String",
      "description": "这是字符串名称啊.",
      "sourceType": "com.ljw.starter.properties.HelloProperties",
      "defaultValue": "hello 默认值！这里配置的是提示，真正默认值在Properties里面"
    },
    {
      "name": "ljw.config.age",
      "type": "java.lang.Integer",
      "description": "这是int类型的年龄啊.",
      "sourceType": "com.ljw.starter.properties.HelloProperties",
      "defaultValue": 8,
      "deprecated": true,
      "deprecation": {
        "level": "warning",
        "reason": "过时原因.",
        "replacement": "替代key是：ljw.config.age22"
      }
    }
  ],
  "hints": []
}

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <!--        测试web应用-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!--自定义satrter-->
    <dependency>
        <groupId>com.ljw</groupId>
        <artifactId>ljw-spring-boot-starter</artifactId>
        <version>1.0</version>
    </dependency>
</dependencies>

@Service
public class TestController implements CommandLineRunner {
    /**
     * 注入自定义starter服务
     */
    @Resource
    private HelloService helloService;
    @Override
    public void run(String... args) throws Exception {
        System.out.println(helloService.hello());
    }
}

ljw.config.name=ljw hello!
ljw.config.age=99
ljw.config.flag=true
#不会注入
#ljw.config.flag=true1
# 可以看到哪些自动配置了
debug=true

HelloService{name='ljw hello!', age=99}

   HelloAutoConfiguration matched:
      - @ConditionalOnClass found required class 'com.ljw.starter.service.HelloService' (OnClassCondition)
      - @ConditionalOnWebApplication (required) found 'session' scope (OnWebApplicationCondition)
      - @ConditionalOnProperty (ljw.config.flag=true) matched (OnPropertyCondition)
   HelloAutoConfiguration#helloService matched:
      - @ConditionalOnMissingBean (types: com.ljw.starter.service.HelloService; SearchStrategy: all) did not find any beans (OnBeanCondition)