@Configuration//開(kāi)啟配置
@EnableConfigurationProperties(HelloProperties.class)//開(kāi)啟使用映射實(shí)體對(duì)象
@ConditionalOnClass(TestHello.class)//存在TestHello時(shí)初始化該配置類
@ConditionalOnProperty//存在對(duì)應(yīng)配置信息時(shí)初始化該配置類
(
        prefix = "zxp.hello",//存在配置前綴zxp.hello
        value = "flag"
)
public class HelloAutoConfiguration {
    @Autowired
    private HelloProperties helloProperties;

    @Bean//創(chuàng)建HelloService實(shí)體bean
    @ConditionalOnMissingBean(TestHello.class)//缺失HelloService實(shí)體bean時(shí)，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;
    }
}

#配置自定義Starter的自動(dòng)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//存在對(duì)應(yīng)配置信息時(shí)初始化該配置類
(
        prefix = "zxp.hello",//存在配置前綴hello  
        value = "flag"http://開(kāi)啟
)

zxp.hello.flag=2

name is null flag is 1

@ConditionalOnBean：當(dāng)SpringIoc容器內(nèi)存在指定Bean的條件
@ConditionalOnSingleCandidate：當(dāng)指定Bean在SpringIoc容器內(nèi)只有一個(gè)，或者雖然有多個(gè)但是指定首選的Bean
@ConditionalOnMissingBean：當(dāng)SpringIoc容器內(nèi)不存在指定Bean的條件

@ConditionalOnClass：當(dāng)SpringIoc容器內(nèi)存在指定Class的條件
@ConditionalOnMissingClass：當(dāng)SpringIoc容器內(nèi)不存在指定Class的條件
@ConditionalOnExpression：基于SpEL表達(dá)式作為判斷條件
@ConditionalOnJava：基于JVM版本作為判斷條件
@ConditionalOnJndi：在JNDI存在時(shí)查找指定的位置
@ConditionalOnResource：類路徑是否有指定的值
@ConditionalOnProperty：指定的屬性是否有指定的值

@ConditionalOnNotWebApplication：當(dāng)前項(xiàng)目不是Web項(xiàng)目的條件
@ConditionalOnWebApplication：當(dāng)前項(xiàng)目是Web項(xiàng)目的條件

@AutoConfigureBefore
@AutoConfigureAfter
@AutoConfigureOrder

public @interface ConditionalOnProperty {
    String[] value() default {}; //數(shù)組，獲取對(duì)應(yīng)property名稱的值，與name不可同時(shí)使用  
    String prefix() default "";//property名稱的前綴，可有可無(wú)  
    String[] name() default {};//數(shù)組，property完整名稱或部分名稱（可與prefix組合使用，組成完整的property名稱），與value不可同時(shí)使用  
    String havingValue() default "";//可與name組合使用，比較獲取到的屬性值與havingValue給定的值是否相同，相同才加載配置  
    boolean matchIfMissing() default false;//缺少該property時(shí)是否可以加載。如果為true，沒(méi)有該property也會(huì)正常加載；反之報(bào)錯(cuò)  
    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 {