Spring 原始碼解析十四：SpringBoot Autoconfigure 初始化應用時載入的元件

這些元件定義在 spring.factories
中

# 初始化器
org.springframework.context.ApplicationContextInitializer=\
org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,\
org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener

# 應用事件監聽器
org.springframework.context.ApplicationListener=\
org.springframework.boot.autoconfigure.BackgroundPreinitializer

# 自動配置匯入監聽器
org.springframework.boot.autoconfigure.AutoConfigurationImportListener=\
org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener

# 自動配置匯入過濾器
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\
org.springframework.boot.autoconfigure.condition.OnBeanCondition,\
org.springframework.boot.autoconfigure.condition.OnClassCondition,\
org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition

# 自動配置
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.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,\
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\
org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\
org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\
org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\
org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\
org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,\
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.neo4j.Neo4jAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration,\
org.springframework.boot.autoconfigure.r2dbc.R2dbcTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,\
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration

# 失敗分析器
org.springframework.boot.diagnostics.FailureAnalyzer=\
org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer,\
org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,\
org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,\
org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBeanCreationFailureAnalyzer,\
org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer

# 檢查模板可用提供器
org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.web.servlet.JspTemplateAvailabilityProvider

1. 初始化器

org.springframework.context.ApplicationContextInitializer=\
org.springframework.boot.autoconfigure.SharedMetadataReaderFactoryContextInitializer,\
org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener

1.1. SharedMetadataReaderFactoryContextInitializer

SharedMetadataReaderFactoryContextInitializer
的主要功能是提供一個共享的快取元資訊讀取工廠

class SharedMetadataReaderFactoryContextInitializer
        implements ApplicationContextInitializer<ConfigurableApplicationContext>, Ordered {
    // 初始化
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        BeanFactoryPostProcessor postProcessor = new CachingMetadataReaderFactoryPostProcessor(applicationContext);
        applicationContext.addBeanFactoryPostProcessor(postProcessor);
    }

    static class CachingMetadataReaderFactoryPostProcessor
            implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
        // 註冊bean定義
        @Override
        public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
            // 註冊bean定義註冊器
            register(registry);
            // 配置 @Configuration bean
            configureConfigurationClassPostProcessor(registry);
        }

        // 註冊bean定義註冊器
        private void register(BeanDefinitionRegistry registry) {
            BeanDefinition definition = BeanDefinitionBuilder
                    .genericBeanDefinition(SharedMetadataReaderFactoryBean.class, SharedMetadataReaderFactoryBean::new)
                    .getBeanDefinition();
            // 註冊為 "org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory" 名字
            registry.registerBeanDefinition(BEAN_NAME, definition);
        }

        // 配置 @Configuration bean
        private void configureConfigurationClassPostProcessor(BeanDefinitionRegistry registry) {
            try {
                // 配置bean "org.springframework.context.annotation.internalConfigurationAnnotationProcessor"
                configureConfigurationClassPostProcessor(
                        registry.getBeanDefinition(AnnotationConfigUtils.CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
            }
            catch (NoSuchBeanDefinitionException ex) {
            }
        }
    }
}

1.2. ConditionEvaluationReportLoggingListener

ConditionEvaluationReportLoggingListener
的主要功能是輸出日誌到檔案

2. 應用事件監聽器

org.springframework.context.ApplicationListener=\
org.springframework.boot.autoconfigure.BackgroundPreinitializer

BackgroundPreinitializer
的主要功能是初始化資料轉換與編碼等服務

public class BackgroundPreinitializer implements ApplicationListener<SpringApplicationEvent> {
    @Override
    public void onApplicationEvent(SpringApplicationEvent event) {
        // ... 程式碼省略

        if (event instanceof ApplicationEnvironmentPreparedEvent
                && preinitializationStarted.compareAndSet(false, true)) {
            performPreinitialization();
        }
        if ((event instanceof ApplicationReadyEvent || event instanceof ApplicationFailedEvent)
                && preinitializationStarted.get()) {
            try {
                preinitializationComplete.await();
            }
            catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
        }
    }

    // 初始化其他元件
    private void performPreinitialization() {
        try {
            Thread thread = new Thread(new Runnable() {

                @Override
                public void run() {
                    // 初始化資料轉換服務，DefaultFormattingConversionService
                    runSafely(new ConversionServiceInitializer());
                    // 初始化資料驗證服務，Validation.byDefaultProvider()
                    runSafely(new ValidationInitializer());
                    // 初始化訊息轉換服務，AllEncompassingFormHttpMessageConverter
                    runSafely(new MessageConverterInitializer());
                    // 初始化JSON服務，Jackson2ObjectMapperBuilder
                    runSafely(new JacksonInitializer());
                    // 初始化字元編碼服務，StandardCharsets
                    runSafely(new CharsetInitializer());
                    preinitializationComplete.countDown();
                }

                public void runSafely(Runnable runnable) {
                    try {
                        runnable.run();
                    }
                    catch (Throwable ex) {}
                }

            }, "background-preinit");
            thread.start();
        }
        catch (Exception ex) {
            // ... 程式碼省略
        }
    }

    private static class MessageConverterInitializer implements Runnable {
        @Override
        public void run() {
            new AllEncompassingFormHttpMessageConverter();
        }
    }

    private static class ValidationInitializer implements Runnable {
        @Override
        public void run() {
            Configuration<?> configuration = Validation.byDefaultProvider().configure();
            configuration.buildValidatorFactory().getValidator();
        }
    }

    private static class JacksonInitializer implements Runnable {
        @Override
        public void run() {
            Jackson2ObjectMapperBuilder.json().build();
        }
    }

    private static class ConversionServiceInitializer implements Runnable {
        @Override
        public void run() {
            new DefaultFormattingConversionService();
        }
    }

    private static class CharsetInitializer implements Runnable {
        @Override
        public void run() {
            StandardCharsets.UTF_8.name();
        }
    }
}

3. 自動配置匯入監聽器

org.springframework.boot.autoconfigure.AutoConfigurationImportListener=\
org.springframework.boot.autoconfigure.condition.ConditionEvaluationReportAutoConfigurationImportListener

ConditionEvaluationReportAutoConfigurationImportListener
的主要功能是從 Report 中讀取結果

4. 自動配置匯入過濾器

org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\
org.springframework.boot.autoconfigure.condition.OnBeanCondition,\
org.springframework.boot.autoconfigure.condition.OnClassCondition,\
org.springframework.boot.autoconfigure.condition.OnWebApplicationCondition

4.1. OnBeanCondition

OnBeanCondition
的主要功能是處理註解 @ConditionalOnBean、@ConditionalOnMissingBean、@ConditionalOnSingleCandidate，按條件動態載入 bean

• @ConditionOnBean 判斷條件 bean 存在，注入當下註解的 bean
• @ConditionOnMissingBean 判斷條件 bean 不存在，才注入當下註解的 bean
• @ConditionalOnSingleCandidate 判斷條件 bean 只能有一個例項或多個但只有一個 primary 例項，才注入當下註解的 bean

先來看看繼承關係

- SpringBootCondition
  - FilteringSpringBootCondition
    - OnBeanCondition

4.1.1. SpringBootCondition

SpringBootCondition
是用條件來檢查元件的基礎類

public abstract class SpringBootCondition implements Condition {
    // 元資訊代表的元件是否匹配
    @Override
    public final boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        // 獲取類名或方法名
        String classOrMethodName = getClassOrMethodName(metadata);
        try {
            // 獲取匹配結果
            ConditionOutcome outcome = getMatchOutcome(context, metadata);

            // ... 程式碼省略

            // 返回是否匹配
            return outcome.isMatch();
        }
        catch (NoClassDefFoundError ex) {
            // ... 程式碼省略
        }

        // ... 程式碼省略
    }

    // 獲取匹配結果，由子類實現
    public abstract ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata);
}

4.1.2. FilteringSpringBootCondition

FilteringSpringBootCondition
的主要功能是新增過濾功能

abstract class FilteringSpringBootCondition extends SpringBootCondition
        implements AutoConfigurationImportFilter, BeanFactoryAware, BeanClassLoaderAware {
    // 元資訊代表的元件是否匹配
    @Override
    public boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata) {
        // 獲取結果
        ConditionOutcome[] outcomes = getOutcomes(autoConfigurationClasses, autoConfigurationMetadata);
        boolean[] match = new boolean[outcomes.length];
        for (int i = 0; i < outcomes.length; i++) {
            // 如果返回為null或true，則表示匹配
            match[i] = (outcomes[i] == null || outcomes[i].isMatch());
            // ... 程式碼省略
        }
        return match;
    }

    // 獲取結果，由子類實現
    protected abstract ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
            AutoConfigurationMetadata autoConfigurationMetadata);
}

4.1.3. SpringBootCondition

SpringBootCondition
的主要功能是處理註解 @ConditionalOnBean、@ConditionalOnMissingBean、@ConditionalOnSingleCandidate，按條件動態載入 bean

class OnBeanCondition extends FilteringSpringBootCondition implements ConfigurationCondition {
    // 獲取結果
    @Override
    protected final ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
            AutoConfigurationMetadata autoConfigurationMetadata) {
        // 結果集
        ConditionOutcome[] outcomes = new ConditionOutcome[autoConfigurationClasses.length];
        for (int i = 0; i < outcomes.length; i++) {
            // 自動配置類
            String autoConfigurationClass = autoConfigurationClasses[i];
            if (autoConfigurationClass != null) {
                // 獲取ConditionalOnBean的bean型別
                Set<String> onBeanTypes = autoConfigurationMetadata.getSet(autoConfigurationClass, "ConditionalOnBean");
                // 確定有沒有ConditionalOnBean的bean型別
                outcomes[i] = getOutcome(onBeanTypes, ConditionalOnBean.class);
                if (outcomes[i] == null) {
                    // 獲取ConditionalOnSingleCandidate的bean型別
                    Set<String> onSingleCandidateTypes = autoConfigurationMetadata.getSet(autoConfigurationClass,
                            "ConditionalOnSingleCandidate");
                    // 確定有沒有ConditionalOnSingleCandidate的bean型別
                    outcomes[i] = getOutcome(onSingleCandidateTypes, ConditionalOnSingleCandidate.class);
                }
            }
        }
        return outcomes;
    }
}

class OnBeanCondition extends FilteringSpringBootCondition implements ConfigurationCondition {
    // 獲取匹配結果
    @Override
    public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
        // 匹配資訊
        ConditionMessage matchMessage = ConditionMessage.empty();
        // 元資訊中的註解
        MergedAnnotations annotations = metadata.getAnnotations();
        // 有@ConditionalOnBean註解
        if (annotations.isPresent(ConditionalOnBean.class)) {
            // 建立ConditionalOnBean的匹配標準物件
            Spec<ConditionalOnBean> spec = new Spec<>(context, metadata, annotations, ConditionalOnBean.class);
            // 獲取匹配的bean
            MatchResult matchResult = getMatchingBeans(context, spec);
            // 如果一個都沒有匹配到
            if (!matchResult.isAllMatched()) {
                // 返回匹配不到的資訊
                String reason = createOnBeanNoMatchReason(matchResult);
                return ConditionOutcome.noMatch(spec.message().because(reason));
            }
            // 匹配到了，繼續
            matchMessage = spec.message(matchMessage).found("bean", "beans").items(Style.QUOTE,
                    matchResult.getNamesOfAllMatches());
        }
        // 有@ConditionalOnSingleCandidate註解
        if (metadata.isAnnotated(ConditionalOnSingleCandidate.class.getName())) {
            // 建立ConditionalOnSingleCandidate的匹配標準物件
            Spec<ConditionalOnSingleCandidate> spec = new SingleCandidateSpec(context, metadata, annotations);
            // 獲取匹配的bean
            MatchResult matchResult = getMatchingBeans(context, spec);
            // 如果一個都沒有匹配到
            if (!matchResult.isAllMatched()) {
                // 返回匹配不到的資訊
                return ConditionOutcome.noMatch(spec.message().didNotFind("any beans").atAll());
            }
            // 匹配到多個bean，但沒有primary bean
            else if (!hasSingleAutowireCandidate(context.getBeanFactory(), matchResult.getNamesOfAllMatches(),
                    spec.getStrategy() == SearchStrategy.ALL)) {
                // 返回匹配到多個的資訊
                return ConditionOutcome.noMatch(spec.message().didNotFind("a primary bean from beans")
                        .items(Style.QUOTE, matchResult.getNamesOfAllMatches()));
            }
            // 匹配到了，繼續
            matchMessage = spec.message(matchMessage).found("a primary bean from beans").items(Style.QUOTE,
                    matchResult.getNamesOfAllMatches());
        }
        // 有@ConditionalOnMissingBean註解
        if (metadata.isAnnotated(ConditionalOnMissingBean.class.getName())) {
            // 建立ConditionalOnMissingBean的匹配標準物件
            Spec<ConditionalOnMissingBean> spec = new Spec<>(context, metadata, annotations,
                    ConditionalOnMissingBean.class);
            // 獲取匹配的bean
            MatchResult matchResult = getMatchingBeans(context, spec);
            // 如果匹配到了
            if (matchResult.isAnyMatched()) {
                // 返回匹配到了的資訊
                String reason = createOnMissingBeanNoMatchReason(matchResult);
                return ConditionOutcome.noMatch(spec.message().because(reason));
            }
            // 匹配不到，繼續
            matchMessage = spec.message(matchMessage).didNotFind("any beans").atAll();
        }
        return ConditionOutcome.match(matchMessage);
    }
}

4.2. OnClassCondition

OnClassCondition
的主要功能是處理註解 @ConditionalOnClass、@ConditionalOnMissingClass，按條件動態載入 bean

• @ConditionalOnClass 判斷條件類存在，注入當下註解的 bean
• @ConditionalOnMissingClass 判斷條件類不存在，才注入當下註解的 bean

class OnClassCondition extends FilteringSpringBootCondition {
    // 獲取結果
    @Override
    protected final ConditionOutcome[] getOutcomes(String[] autoConfigurationClasses,
            AutoConfigurationMetadata autoConfigurationMetadata) {
        // ... 程式碼省略

        OutcomesResolver outcomesResolver = new StandardOutcomesResolver(autoConfigurationClasses, 0,
                autoConfigurationClasses.length, autoConfigurationMetadata, getBeanClassLoader());
        // 獲取ConditionalOnClass的輸出
        return outcomesResolver.resolveOutcomes();

    }

    // 獲取匹配結果
    @Override
    public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
        ClassLoader classLoader = context.getClassLoader();
        // 匹配資訊
        ConditionMessage matchMessage = ConditionMessage.empty();
        // 獲取標記有@ConditionalOnClass註解的類
        List<String> onClasses = getCandidates(metadata, ConditionalOnClass.class);
        if (onClasses != null) {
            List<String> missing = filter(onClasses, ClassNameFilter.MISSING, classLoader);
            // 類不存在，返回
            if (!missing.isEmpty()) {
                return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnClass.class)
                        .didNotFind("required class", "required classes").items(Style.QUOTE, missing));
            }
            // 類存在，繼續
            matchMessage = matchMessage.andCondition(ConditionalOnClass.class)
                    .found("required class", "required classes")
                    .items(Style.QUOTE, filter(onClasses, ClassNameFilter.PRESENT, classLoader));
        }
        // 獲取標記有@ConditionalOnMissingClass註解的類
        List<String> onMissingClasses = getCandidates(metadata, ConditionalOnMissingClass.class);
        if (onMissingClasses != null) {
            List<String> present = filter(onMissingClasses, ClassNameFilter.PRESENT, classLoader);
            // 類存在，返回
            if (!present.isEmpty()) {
                return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnMissingClass.class)
                        .found("unwanted class", "unwanted classes").items(Style.QUOTE, present));
            }
            // 類不存在，繼續
            matchMessage = matchMessage.andCondition(ConditionalOnMissingClass.class)
                    .didNotFind("unwanted class", "unwanted classes")
                    .items(Style.QUOTE, filter(onMissingClasses, ClassNameFilter.MISSING, classLoader));
        }
        return ConditionOutcome.match(matchMessage);
    }

}

4.3. OnWebApplicationCondition

OnWebApplicationCondition
的主要功能是處理註解 @ConditionalOnWebApplication、@ConditionalOnNotWebApplication，按條件動態載入 bean

• @ConditionalOnWebApplication 判斷應用時 Web 應用時，注入當下註解的 bean
• @ConditionalOnNotWebApplication 判斷應用時不是 Web 應用時，才注入當下註解的 bean

5. 自動配置

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.context.ConfigurationPropertiesAutoConfiguration,\
org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,\
org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration,\
org.springframework.boot.autoconfigure.couchbase.CouchbaseAutoConfiguration,\
org.springframework.boot.autoconfigure.dao.PersistenceExceptionTranslationAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jReactiveDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jReactiveRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcDataAutoConfiguration,\
org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration,\
org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.data.web.SpringDataWebAutoConfiguration,\
org.springframework.boot.autoconfigure.elasticsearch.ElasticsearchRestClientAutoConfiguration,\
org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
org.springframework.boot.autoconfigure.h2.H2ConsoleAutoConfiguration,\
org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastAutoConfiguration,\
org.springframework.boot.autoconfigure.hazelcast.HazelcastJpaDependencyAutoConfiguration,\
org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration,\
org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\
org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\
org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration,\
org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\
org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JmsAutoConfiguration,\
org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.JndiConnectionFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.activemq.ActiveMQAutoConfiguration,\
org.springframework.boot.autoconfigure.jms.artemis.ArtemisAutoConfiguration,\
org.springframework.boot.autoconfigure.jersey.JerseyAutoConfiguration,\
org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\
org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\
org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\
org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration,\
org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration,\
org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderAutoConfiguration,\
org.springframework.boot.autoconfigure.mail.MailSenderValidatorAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\
org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\
org.springframework.boot.autoconfigure.neo4j.Neo4jAutoConfiguration,\
org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\
org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\
org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration,\
org.springframework.boot.autoconfigure.r2dbc.R2dbcTransactionManagerAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,\
org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\
org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration,\
org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,\
org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\
org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,\
org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,\
org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration,\
org.springframework.boot.autoconfigure.transaction.jta.JtaAutoConfiguration,\
org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration,\
org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration,\
org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration,\
org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\
org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration,\
org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration

• SpringApplicationAdminJmxAutoConfiguration
• AopAutoConfiguration
• RabbitAutoConfiguration
• BatchAutoConfiguration
• CacheAutoConfiguration
• CassandraAutoConfiguration
• ConfigurationPropertiesAutoConfiguration
• LifecycleAutoConfiguration
• MessageSourceAutoConfiguration
• PropertyPlaceholderAutoConfiguration
• CouchbaseAutoConfiguration
• PersistenceExceptionTranslationAutoConfiguration
• CassandraDataAutoConfiguration
• CassandraReactiveDataAutoConfiguration
• CassandraReactiveRepositoriesAutoConfiguration
• CassandraRepositoriesAutoConfiguration
• CouchbaseDataAutoConfiguration
• CouchbaseReactiveDataAutoConfiguration
• CouchbaseReactiveRepositoriesAutoConfiguration
• CouchbaseRepositoriesAutoConfiguration
• ElasticsearchDataAutoConfiguration
• ElasticsearchRepositoriesAutoConfiguration
• ReactiveElasticsearchRepositoriesAutoConfiguration
• ReactiveElasticsearchRestClientAutoConfiguration
• JdbcRepositoriesAutoConfiguration
• JpaRepositoriesAutoConfiguration
• LdapRepositoriesAutoConfiguration
• MongoDataAutoConfiguration
• MongoReactiveDataAutoConfiguration
• MongoReactiveRepositoriesAutoConfiguration
• MongoRepositoriesAutoConfiguration
• Neo4jDataAutoConfiguration
• Neo4jReactiveDataAutoConfiguration
• Neo4jReactiveRepositoriesAutoConfiguration
• Neo4jRepositoriesAutoConfiguration
• R2dbcDataAutoConfiguration
• R2dbcRepositoriesAutoConfiguration
• RedisAutoConfiguration
• RedisReactiveAutoConfiguration
• RedisRepositoriesAutoConfiguration
• RepositoryRestMvcAutoConfiguration
• SpringDataWebAutoConfiguration
• ElasticsearchRestClientAutoConfiguration
• FlywayAutoConfiguration
• FreeMarkerAutoConfiguration
• GroovyTemplateAutoConfiguration
• GsonAutoConfiguration
• H2ConsoleAutoConfiguration
• HypermediaAutoConfiguration
• HazelcastAutoConfiguration
• HazelcastJpaDependencyAutoConfiguration
• HttpMessageConvertersAutoConfiguration
• CodecsAutoConfiguration
• InfluxDbAutoConfiguration
• ProjectInfoAutoConfiguration
• IntegrationAutoConfiguration
• JacksonAutoConfiguration
• DataSourceAutoConfiguration
• JdbcTemplateAutoConfiguration
• JndiDataSourceAutoConfiguration
• XADataSourceAutoConfiguration
• DataSourceTransactionManagerAutoConfiguration
• JmsAutoConfiguration
• JmxAutoConfiguration
• JndiConnectionFactoryAutoConfiguration
• ActiveMQAutoConfiguration
• ArtemisAutoConfiguration
• JerseyAutoConfiguration
• JooqAutoConfiguration
• JsonbAutoConfiguration
• KafkaAutoConfiguration
• ApplicationAvailabilityAutoConfiguration
• EmbeddedLdapAutoConfiguration
• LdapAutoConfiguration
• LiquibaseAutoConfiguration
• MailSenderAutoConfiguration
• MailSenderValidatorAutoConfiguration
• EmbeddedMongoAutoConfiguration
• MongoAutoConfiguration
• MongoReactiveAutoConfiguration
• MustacheAutoConfiguration
• Neo4jAutoConfiguration
• HibernateJpaAutoConfiguration
• QuartzAutoConfiguration
• R2dbcAutoConfiguration
• R2dbcTransactionManagerAutoConfiguration
• RSocketMessagingAutoConfiguration
• RSocketRequesterAutoConfiguration
• RSocketServerAutoConfiguration
• RSocketStrategiesAutoConfiguration
• SecurityAutoConfiguration
• UserDetailsServiceAutoConfiguration
• SecurityFilterAutoConfiguration
• ReactiveSecurityAutoConfiguration
• ReactiveUserDetailsServiceAutoConfiguration
• RSocketSecurityAutoConfiguration
• Saml2RelyingPartyAutoConfiguration
• SendGridAutoConfiguration
• SessionAutoConfiguration
• OAuth2ClientAutoConfiguration
• ReactiveOAuth2ClientAutoConfiguration
• OAuth2ResourceServerAutoConfiguration
• ReactiveOAuth2ResourceServerAutoConfiguration
• SolrAutoConfiguration
• TaskExecutionAutoConfiguration
• TaskSchedulingAutoConfiguration
• ThymeleafAutoConfiguration
• TransactionAutoConfiguration
• JtaAutoConfiguration
• ValidationAutoConfiguration
• RestTemplateAutoConfiguration
• EmbeddedWebServerFactoryCustomizerAutoConfiguration
• HttpHandlerAutoConfiguration
• ReactiveWebServerFactoryAutoConfiguration
• WebFluxAutoConfiguration
• ErrorWebFluxAutoConfiguration
• ClientHttpConnectorAutoConfiguration
• WebClientAutoConfiguration
• DispatcherServletAutoConfiguration
• ServletWebServerFactoryAutoConfiguration
• ErrorMvcAutoConfiguration
• HttpEncodingAutoConfiguration
• MultipartAutoConfiguration
• WebMvcAutoConfiguration
• WebSocketReactiveAutoConfiguration
• WebSocketServletAutoConfiguration
• WebSocketMessagingAutoConfiguration
• WebServicesAutoConfiguration
• WebServiceTemplateAutoConfiguration

以上的類都是通過 application*.yaml 中的屬性配置自動裝載成 bean。這些類比較多，可以自行探索

6. 失敗分析器

org.springframework.boot.diagnostics.FailureAnalyzer=\
org.springframework.boot.autoconfigure.data.redis.RedisUrlSyntaxFailureAnalyzer,\
org.springframework.boot.autoconfigure.diagnostics.analyzer.NoSuchBeanDefinitionFailureAnalyzer,\
org.springframework.boot.autoconfigure.flyway.FlywayMigrationScriptMissingFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.DataSourceBeanCreationFailureAnalyzer,\
org.springframework.boot.autoconfigure.jdbc.HikariDriverConfigurationFailureAnalyzer,\
org.springframework.boot.autoconfigure.r2dbc.ConnectionFactoryBeanCreationFailureAnalyzer,\
org.springframework.boot.autoconfigure.session.NonUniqueSessionRepositoryFailureAnalyzer

• RedisUrlSyntaxFailureAnalyzer
  Redis url 語法錯誤
• NoSuchBeanDefinitionFailureAnalyzer
  沒有 bean 定義
• FlywayMigrationScriptMissingFailureAnalyzer
  Flyway 沒有可用的 sql 指令碼
• DataSourceBeanCreationFailureAnalyzer
  資料庫源 bean 建立失敗
• HikariDriverConfigurationFailureAnalyzer
  HikariCP 配置失敗
• ConnectionFactoryBeanCreationFailureAnalyzer
  ConnectionFactory bean 建立失敗
• NonUniqueSessionRepositoryFailureAnalyzer
  多個 Spring Session 錯誤

這些類都比較簡單，可以自行探索

7. 檢查模板可用提供器

org.springframework.boot.autoconfigure.template.TemplateAvailabilityProvider=\
org.springframework.boot.autoconfigure.freemarker.FreeMarkerTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.mustache.MustacheTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.thymeleaf.ThymeleafTemplateAvailabilityProvider,\
org.springframework.boot.autoconfigure.web.servlet.JspTemplateAvailabilityProvider

• FreeMarkerTemplateAvailabilityProvider
  FreeMarker 模板檢查
• MustacheTemplateAvailabilityProvider
  Mustache 模板檢查
• GroovyTemplateAvailabilityProvider
  Groovy 模板檢查
• ThymeleafTemplateAvailabilityProvider
  Thymeleaf 模板檢查
• JspTemplateAvailabilityProvider
  Jsp 模板檢查

這些類都比較簡單，可以自行探索

後續

更多部落格，檢視 https://github.com/senntyou/blogs

作者：深予之 (@senntyou)

版權宣告：自由轉載-非商用-非衍生-保持署名（創意共享 3.0 許可證）