Spring Boot如何排除自動加載數據源

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前言

有些老項目使用Spring MVC裡面有寫好的數據庫連接池，比如redis/mongodb/mybatis(mysql其他Oracle同理)。在這些項目遷入spring boot框架時，會報錯。

原因是我們業務寫好瞭連接池，但spring boot在jar包存在的時候會主動加載spring boot的autoconfiguration創建連接池，但我們並未配置Spring Boot參數，也不需要配置。

1. mongodb

mongodb自動配置錯誤如下：

org.mongodb.driver.cluster : Exception in monitor thread while connecting to server localhost:27017
com.mongodb.MongoSocketOpenException: Exception opening socket
Caused by: java.net.ConnectException: Connection refused (Connection refused)

但是我沒有引入spring-boot-starter-data-mongodb的jar包，後來發現我引入瞭spring-data-mongodb的jar

檢查spring-boot-starter-data-mongodb的jar，包括3部分，如下：

我的jar包都有，相當於這些jar拼裝成瞭 spring-boot-starter-data-mongodb

在Spring Boot中自動引入瞭自動配置功能

需要手動排除自動配置的數據源，在SpringBootApplication中exclude

@SpringBootApplication(exclude = {MongoAutoConfiguration.class, MongoDataAutoConfiguration.class})

啟動不再報錯連接localhost:27017，業務正常。原理見Spring Boot官方文檔

2. mybatis

mybatis同理

Failed to auto-configure a DataSource: ‘spring.datasource.url’ is not specified and no embedded data

***************************
APPLICATION FAILED TO START
***************************

Description:

Cannot determine embedded database driver class for database type NONE

Action:

If you want an embedded database please put a supported one on the classpath. If you have database settings to be loaded from a particular profile you may need to active it (no profiles are currently active).

需要排除

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})

3. 原理講解

原理是EnableAutoConfiguration

進一步跟蹤：

AutoConfigurationImportSelector這個類有自動加載與排除的邏輯

public String[] selectImports(AnnotationMetadata annotationMetadata) {
if (!isEnabled(annotationMetadata)) {
return NO_IMPORTS;
}
AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
.loadMetadata(this.beanClassLoader);
AutoConfigurationEntry autoConfigurationEntry = getAutoConfigurationEntry(autoConfigurationMetadata,
annotationMetadata);
return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());
}

註意加載代碼

getAutoConfigurationEntry(autoConfigurationMetadata, annotationMetadata);
/**
	 * Return the {@link AutoConfigurationEntry} based on the {@link AnnotationMetadata}
	 * of the importing {@link Configuration @Configuration} class.
	 * @param autoConfigurationMetadata the auto-configuration metadata
	 * @param annotationMetadata the annotation metadata of the configuration class
	 * @return the auto-configurations that should be imported
	 */
	protected AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata,
			AnnotationMetadata annotationMetadata) {
		if (!isEnabled(annotationMetadata)) {
			return EMPTY_ENTRY;
		}
		AnnotationAttributes attributes = getAttributes(annotationMetadata);
		List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
		configurations = removeDuplicates(configurations);
		Set<String> exclusions = getExclusions(annotationMetadata, attributes);
		checkExcludedClasses(configurations, exclusions);
		configurations.removeAll(exclusions);
		configurations = filter(configurations, autoConfigurationMetadata);
		fireAutoConfigurationImportEvents(configurations, exclusions);
		return new AutoConfigurationEntry(configurations, exclusions);
	}

裡面

getExclusions(annotationMetadata, attributes);
/**
	 * Return any exclusions that limit the candidate configurations.
	 * @param metadata the source metadata
	 * @param attributes the {@link #getAttributes(AnnotationMetadata) annotation
	 * attributes}
	 * @return exclusions or an empty set
	 */
	protected Set<String> getExclusions(AnnotationMetadata metadata, AnnotationAttributes attributes) {
		Set<String> excluded = new LinkedHashSet<>();
		excluded.addAll(asList(attributes, "exclude"));
		excluded.addAll(Arrays.asList(attributes.getStringArray("excludeName")));
		excluded.addAll(getExcludeAutoConfigurationsProperty());
		return excluded;
	}

看到瞭，exclude或者excludeName，當然還有一種方法

private List<String> getExcludeAutoConfigurationsProperty() {
		if (getEnvironment() instanceof ConfigurableEnvironment) {
			Binder binder = Binder.get(getEnvironment());
			return binder.bind(PROPERTY_NAME_AUTOCONFIGURE_EXCLUDE, String[].class).map(Arrays::asList)
					.orElse(Collections.emptyList());
		}
		String[] excludes = getEnvironment().getProperty(PROPERTY_NAME_AUTOCONFIGURE_EXCLUDE, String[].class);
		return (excludes != null) ? Arrays.asList(excludes) : Collections.emptyList();
	}

通過application.properties文件配置spring.autoconfigure.exclude

private static final String PROPERTY_NAME_AUTOCONFIGURE_EXCLUDE = "spring.autoconfigure.exclude";

總結

出現這種錯誤多半發生在引入瞭spring-boot-starter-mongodb等這樣的starter插件jar，沒有配置數據源url；或者舊業務升級spring boot（筆者就是這種情況）

解決方法

不需要的jar不要引入即可解決問題

使用exclude排除，有三種實現方式exclude、excludeName、spring.autoconfigure.exclude

以上為個人經驗，希望能給大傢一個參考，也希望大傢多多支持WalkonNet。

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