Spring Boot自动配置原理、实战

org.springframework.core.io.support.SpringFactoriesLoader.loadFactoryNames(Class<?>, ClassLoader)

public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) {
    String factoryClassName = factoryClass.getName();
    try {
        Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
                lassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
        List<String> result = new ArrayList<String>();
        while (urls.hasMoreElements()) {
            URL url = urls.nextElement();
            Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
            String factoryClassNames = properties.getProperty(factoryClassName);
            result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));
        }
        return result;
    }
    catch (IOException ex) {
        throw new IllegalArgumentException("Unable to load [" + factoryClass.getName() +
                "] factories from location [" + FACTORIES_RESOURCE_LOCATION + "]", ex);
    }
}

/**
 * The location to look for factories.
 * <p>Can be present in multiple JAR files.
 */
public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
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.cloud.CloudAutoConfiguration,\
...

@Configuration
@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })
@EnableConfigurationProperties(DataSourceProperties.class)
@Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class })
public class DataSourceAutoConfiguration {
...

import org.slf4j.Logger;
import org.springframework.context.EnvironmentAware;
import org.springframework.core.env.Environment;

import com.oceanpayment.common.utils.logger.LoggerUtils;

public class EnvConfig implements EnvironmentAware {

    private final Logger logger = LoggerUtils.getLogger(this);

    private Environment env;

    public String getStringValue(String key) {
        return env.getProperty(key);
    }

    public Long getLongValue(String key) {
        String value = getStringValue(key);
        try {
            return Long.parseLong(value);
        } catch (Exception e) {
            logger.error("字符串转换Long失败：{} = {}", key, value);
        }
        return 0L;
    }

    public int getIntValue(String key) {
        return getLongValue(key).intValue();
    }

    @Override
    public void setEnvironment(Environment environment) {
        this.env = environment;
    }

}

import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.PropertyResolver;

@Configuration
@ConditionalOnClass(PropertyResolver.class)
public class EnvAutoConfig {

    @Bean
    public EnvConfig envConfig() {
        return new EnvConfig();
    }

}

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\\
com.oceanpayment.common.config.env.EnvAutoConfig

=========================
AUTO-CONFIGURATION REPORT
=========================


Positive matches:
-----------------

   AopAutoConfiguration matched:
      - @ConditionalOnClass found required classes 'org.springframework.context.annotation.EnableAspectJAutoProxy', 'org.aspectj.lang.annotation.Aspect', 'org.aspectj.lang.reflect.Advice'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
      - @ConditionalOnProperty (spring.aop.auto=true) matched (OnPropertyCondition)

   ...

   EnvAutoConfig matched:
      - @ConditionalOnClass found required class 'org.springframework.core.env.PropertyResolver'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)

   ErrorMvcAutoConfiguration matched:
      - @ConditionalOnClass found required classes 'javax.servlet.Servlet', 'org.springframework.web.servlet.DispatcherServlet'; @ConditionalOnMissingClass did not find unwanted class (OnClassCondition)
      - @ConditionalOnWebApplication (required) found StandardServletEnvironment (OnWebApplicationCondition)

   ErrorMvcAutoConfiguration#basicErrorController matched:
      - @ConditionalOnMissingBean (types: org.springframework.boot.autoconfigure.web.ErrorController; SearchStrategy: current) did not find any beans (OnBeanCondition)

   ...


Negative matches:
-----------------

   ActiveMQAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory', 'org.apache.activemq.ActiveMQConnectionFactory' (OnClassCondition)

   AopAutoConfiguration.JdkDynamicAutoProxyConfiguration:
      Did not match:
         - @ConditionalOnProperty (spring.aop.proxy-target-class=false) found different value in property 'proxy-target-class' (OnPropertyCondition)

   ArtemisAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required classes 'javax.jms.ConnectionFactory', 'org.apache.activemq.artemis.jms.client.ActiveMQConnectionFactory' (OnClassCondition)

   BatchAutoConfiguration:
      Did not match:
         - @ConditionalOnClass did not find required class 'org.springframework.batch.core.launch.JobLauncher' (OnClassCondition)

   ...