Spring Boot如何排除自动加载数据源

目录

• 前言
• 1. mongodb
• 2. mybatis
• 3. 原理讲解
• 总结
• 解决方法

前言

有些老项目使用Spring MVC里面有写好的数据库连接池，比如redis/mongodb/mybatis(mysql其他Oracle同理)。在这些项目迁入spring boot框架时，会报错。

原因是我们业务写好了连接池，但spring boot在jar包存在的时候会主动加载spring boot的autoconfiguration创建连接池，但我们并未配置Spring Boot参数，也不需要配置。

1. mongodb

mongodb自动配置错误如下：

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)

但是我没有引入spring-boot-starter-data-mongodb的jar包，后来发现我引入了spring-data-mongodb的jar

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

我的jar包都有，相当于这些jar拼装成了 spring-boot-starter-data-mongodb

在Spring Boot中自动引入了自动配置功能

需要手动排除自动配置的数据源，在SpringBootApplication中exclude

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

启动不再报错连接localhost:27017，业务正常。原理见Spring Boot官方文档

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. 原理讲解

原理是EnableAutoConfiguration

进一步跟踪：

AutoConfigurationImportSelector这个类有自动加载与排除的逻辑

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());
}

注意加载代码

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);
	}

里面

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;
	}

看到了，exclude或者excludeName，当然还有一种方法

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();
	}

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

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

总结

出现这种错误多半发生在引入了spring-boot-starter-mongodb等这样的starter插件jar，没有配置数据源url；或者旧业务升级spring boot（笔者就是这种情况）

解决方法

不需要的jar不要引入即可解决问题

使用exclude排除，有三种实现方式exclude、excludeName、spring.autoconfigure.exclude

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。