SpringBoot 基本原理--依赖传递与自动配置

// 1. application.properties 文件
server.port=8081
// 2. application.yml 文件
server:
   port: 8082
// 3. application.yaml 文件
server:
   port: 8083

application.yaml（忽略）
application.yml
application.properties
java系统属性（-Dxxx=xxx）
命令行参数（--xxx=xxx）

@Scope("prototype")
@RestController
@RequestMapping("/depts")
public class DeptController {
   // some code
}

@Component
@Controller
@Service
@Repository

// 连包带类创建 config.CommonConfig

@Configuration
public class CommonConfig {
   @Bean
   public SAXReader saxReader(){
      return new SAXReader();
   }
}

// src/main/java/com.example/

// TokenParser.java
package com.exmaple;
import org.springframework.stereotype.Component;
@Component
public class TokenParser {
    public void parse() {
        System.out.println("TokenParser ... parse ...");
    }
}

// HeaderConfig
package com.exmaple;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class HeaderConfig {
    @Bean
    public HeaderGenerator headerGenerator(){
        return new HeaderGenerator();
    }
    @Bean
    public HeaderParser headerParser(){
        return new HeaderParser();
    }
}

// HeaderGenerator
package com.exmaple;
public class HeaderGenerator {
    public void generate(){
        System.out.println("HeaderGenerator ... generate ...");
    }
}

// HeaderParser
package com.exmaple;
public class HeaderParser {
    public void parse(){
        System.out.println("HeaderParser ... parse ...");
    }
}

<dependency>
   <groupId>com.example</groupId>
   <artifactId>mytlias-utils</artifactId>
   <version>1.0-SNAPSHOT</version>
</dependency>

@SpringBootTest
public class AutoConfigTest {
    @Autowired
    private ApplicationContext applicationContext;

    @Autowired
    private Gson gson;

    @Test
    public void testGson(){
        System.out.println(gson.toJson(Result.success()));
    }

    @Test
    public void testTokenParser(){
        System.out.println(applicationContext.getBean(TokenParser.class));
    }

    @Test
    public void testHeaderGenerator(){
        System.out.println(applicationContext.getBean(HeaderGenerator.class));
    }

    @Test
    public void testHeaderParser(){
        System.out.println(applicationContext.getBean(HeaderParser.class));
    }
}

@ComponentScan({"com.example", "com.itheima", "com.alibaba", ...})
@SpringBootApplication
public class SpringbootWebConfig2Application {
   // some code
}

// SpringbootAutoconfigApplication 头部添加注解
@Import(TokenParser.class)     // 导入普通类并交给ioc管理
// com.exmaple.TokenParser@63d3c9dc

@Import(HeaderConfig.class)   // 导入配置类并交给ioc管理
// com.exmaple.HeaderGenerator@1a4cbcc6
// com.exmaple.HeaderParser@3d4818e8

package com.example;

public class UtilsImportSelector implements ImportSelector {

    @Override
    public String[] selectImports(AnnotationMetadata importingClassMetadata) {
        return new String[]{"com.example.HeaderConfig"};
    }
}

package com.example;

import org.springframework.context.annotation.Import;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Import(UtilsImportSelector.class)
public @interface EnableHeaderConfig {
}

@EnableHeaderConfig
@SpringBootApplication
public class SpringbootAutoconfigApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringbootAutoconfigApplication.class, args);
    }
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    ...

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
   ...

public String[] selectImports(AnnotationMetadata annotationMetadata) {
   if (!this.isEnabled(annotationMetadata)) {
      return NO_IMPORTS;
   } else {
      AutoConfigurationEntry autoConfigurationEntry = this.getAutoConfigurationEntry(annotationMetadata);
      return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
   }
}

protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
   if (!this.isEnabled(annotationMetadata)) {
      return EMPTY_ENTRY;
   } else {
      AnnotationAttributes attributes = this.getAttributes(annotationMetadata);
      List<String> configurations = this.getCandidateConfigurations(annotationMetadata, attributes);
      configurations = this.removeDuplicates(configurations);
      Set<String> exclusions = this.getExclusions(annotationMetadata, attributes);
      this.checkExcludedClasses(configurations, exclusions);
      configurations.removeAll(exclusions);
      configurations = this.getConfigurationClassFilter().filter(configurations);
      this.fireAutoConfigurationImportEvents(configurations, exclusions);
      return new AutoConfigurationEntry(configurations, exclusions);
   }
}

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
   List<String> configurations = ImportCandidates.load(AutoConfiguration.class, this.getBeanClassLoader()).getCandidates();
   Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. " +
            "If you are using a custom packaging, make sure that file is correct.");
   return configurations;
}

org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration
org.springframework.boot.autoconfigure.batch.BatchAutoConfiguration
org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration
org.springframework.boot.autoconfigure.cassandra.CassandraAutoConfiguration
org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration
...

<dependency>
   <groupId>com.aliyun.oss</groupId>
   <artifactId>aliyun-sdk-oss</artifactId>
   <version>3.15.1</version>
</dependency>

aliyun:
  oss:
    endpoint: https://oss-cn-beijing.aliyuncs.com/
    accessKeyId: xxx
    accessKeySecret: xxx
    bucketName: rainbow-tlias

<?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>3.1.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.aliyun.oss</groupId>
    <artifactId>aliyun-oss-starter</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>com.aliyun.oss</groupId>
            <artifactId>aliyun-oss-spring-boot-autoconfigure</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
</project>

package com.aliyun.oss;

@EnableConfigurationProperties(AliOSSProperties.class)
@Configuration
public class AliOSSConfiguration {
    @Bean
    public AliOSSUtils aliOSSUtils(AliOSSProperties properties){
        AliOSSUtils aliOSSUtils = new AliOSSUtils();
        aliOSSUtils.setProperties(properties);
        return aliOSSUtils;
    }
}

package com.aliyun.oss;

@ConfigurationProperties(prefix = "aliyun.oss")
public class AliOSSProperties {
    private String endpoint;        // 服务器域名
    private String accessKeyId;     // 访问ID
    private String accessKeySecret; // 访问密钥
    private String bucketName;      // 数据桶名
    ...  // getter setter
}

package com.aliyun.oss;

public class AliOSSUtils {
    private AliOSSProperties properties;
    ...  // getter setter
    public String upload(MultipartFile file) throws IOException {
      // some code
    }

@SpringBootTest
class AliyunOssTestApplicationTests {
    @Autowired
    AliOSSProperties p;
    @Autowired
    private ApplicationContext context;
    @Test
    void testAliConfig() {
        System.out.println(context.getBean(AliOSSConfiguration.class));
    }
    @Test
    void testAliUtil() {
        System.out.println(context.getBean(AliOSSUtils.class));
    }
    @Test
    void testAliProp() {
        System.out.println(context.getBean(AliOSSProperties.class));
        System.out.println(p.getEndpoint());
    }
}