Spring Boot如何排除自动加载数据源

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。