SpringBoot自动装配原理小结

@Configuration//开启配置
@EnableConfigurationProperties(HelloProperties.class)//开启使用映射实体对象
@ConditionalOnClass(TestHello.class)//存在TestHello时初始化该配置类
@ConditionalOnProperty//存在对应配置信息时初始化该配置类
(
        prefix = "zxp.hello",//存在配置前缀zxp.hello
        value = "flag"
)
public class HelloAutoConfiguration {
    @Autowired
    private HelloProperties helloProperties;

    @Bean//创建HelloService实体bean
    @ConditionalOnMissingBean(TestHello.class)//缺失HelloService实体bean时，初始化HelloService并添加到SpringIoc
    public TestHello helloService()
    {
        System.out.println(">>>The TestHello Not Found，Execute Create New Bean.");
        TestHello testHello = new TestHello(helloProperties.getName(),helloProperties.getFlag());
        return testHello;
    }
}

@ConfigurationProperties(prefix = "zxp.hello")
@Data
public class HelloProperties {
    private String name;
    private String flag;
}

public class TestHello {
    String name;
    String flag;

    public TestHello(String name, String flag) {
        this.name = name;
        this.flag = flag;
    }

    public String print(){
        String msg = "name is "+name + "  " + "flag is "+flag;
        System.out.println(msg);
        return msg;
    }
}

#配置自定义Starter的自动化配置
org.springframework.boot.autoconfigure.EnableAutoConfiguration=springbootautoconfig.test.config.HelloAutoConfiguration

- Bean method 'helloService' not loaded because @ConditionalOnProperty (zxp.hello) did not find property 'flag'

@ConditionalOnProperty//存在对应配置信息时初始化该配置类
(
        prefix = "zxp.hello",//存在配置前缀hello  
        value = "flag"//开启
)

zxp.hello.flag=2

name is null flag is 1

@ConditionalOnBean：当SpringIoc容器内存在指定Bean的条件
@ConditionalOnSingleCandidate：当指定Bean在SpringIoc容器内只有一个，或者虽然有多个但是指定首选的Bean
@ConditionalOnMissingBean：当SpringIoc容器内不存在指定Bean的条件

@ConditionalOnClass：当SpringIoc容器内存在指定Class的条件
@ConditionalOnMissingClass：当SpringIoc容器内不存在指定Class的条件
@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存在时查找指定的位置
@ConditionalOnResource：类路径是否有指定的值
@ConditionalOnProperty：指定的属性是否有指定的值

@ConditionalOnNotWebApplication：当前项目不是Web项目的条件
@ConditionalOnWebApplication：当前项目是Web项目的条件

@AutoConfigureBefore
@AutoConfigureAfter
@AutoConfigureOrder

public @interface ConditionalOnProperty {
    String[] value() default {}; //数组，获取对应property名称的值，与name不可同时使用  
    String prefix() default "";//property名称的前缀，可有可无  
    String[] name() default {};//数组，property完整名称或部分名称（可与prefix组合使用，组成完整的property名称），与value不可同时使用  
    String havingValue() default "";//可与name组合使用，比较获取到的属性值与havingValue给定的值是否相同，相同才加载配置  
    boolean matchIfMissing() default false;//缺少该property时是否可以加载。如果为true，没有该property也会正常加载；反之报错  
    boolean relaxedNames() default true;//是否可以松散匹配，至今不知道怎么使用的  
} 

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
   List<String> configurations = SpringFactoriesLoader.loadFactoryNames(getSpringFactoriesLoaderFactoryClass(),
         getBeanClassLoader());
   Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you "
         + "are using a custom packaging, make sure that file is correct.");
   return configurations;
}
public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
    ……
    Enumeration<URL> urls = (classLoader != null ?
      classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
      ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
    result = new LinkedMultiValueMap<>();
    while (urls.hasMoreElements()) {

……
work.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
org.springframework.boot.autoconfigure.aop.AopAutoConfiguration,\
org.springframework.boot.autoconfigure.amqp.RabbitAutoConfiguration,\
……

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass({ RabbitTemplate.class, Channel.class })
@EnableConfigurationProperties(RabbitProperties.class)
@Import(RabbitAnnotationDrivenConfiguration.class)
public class RabbitAutoConfiguration {