1.DataSource配置
1.1 默认配置application.xml
spring.datasource.url=jdbc:mysql://localhost/test spring.datasource.username=root spring.datasource.password=****
spring.datasource.driver-class-name=com.mysql.jdbc.Driver spring.datasource.type=com.zaxxer.hikari.HikariDataSource
需要在pom.xml加入依赖(我使用了mybatis+mysql)
<dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>${mybatis.version}</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis-spring</artifactId> <version>${mybatis-spring.version}</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency>
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<exclusions>
<exclusion>
<artifactId>tools</artifactId>
<groupId>com.sun</groupId>
</exclusion>
</exclusions>
</dependency>
2.自定义DataSource
1.1 application.xml配置文件
spring:
application:
name: data-multidatasource
datasource:
type: com.zaxxer.hikari.HikariDataSource
url: jdbc:mysql://localhost:3306/test
username: sa
password: ****
second-datasource:
driver-class-name: org.hsqldb.jdbc.JDBCDriver
url: jdbc:hsqldb:mem:db2
username: sa
password:****
1.2 自定义DataSource配置
@Configuration public class SencondDataSourceConfiguration { @Bean @ConfigurationProperties(prefix = "spring.datasource") public DataSource newDataSource() { return DataSourceBuilder.create().build(); }@Bean(name </span>= "secondDatasource"<span style="color: #000000;">)</br>@ConfigurationProperties(prefix
= "spring.second-datasource")
public DataSource secondDataSource() {
return DataSourceBuilder.create().build();
}
}
3.工作原理
spring boot的auto-configuration最具魔力的地方是@EnableAutoConfiguration注解
通常注解application应用使用@SpringBootApplication或者如下自定义的方式：
@Configuration@EnableAutoConfiguration
public class Application
@ComponentScan{
}
@EnableAutoConfiguration注解开启了spring ApplicationContext的自动配置功能，
它通过扫描classpath下的组件，满足不同Conditions的bean注册到容器中。
spring boot提供了不同的AutoConfiguration实现类，这些类都在spring-boot-autoconfigure-{version}.jar中，用来注册各种各样的组件。
通常，当AutoConfiguration实现类打上@Configuration标签，可以作为spring配置类，当AutoConfiguration实现类打上@EnableConfigurationProperties标签，可以绑定自定义属性或者更多Conditional bean注册方法。
下面就org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration来分析一下：
/** * {@link EnableAutoConfiguration Auto-configuration} for {@link DataSource}. * * @author Dave Syer * @author Phillip Webb * @author Stephane Nicoll * @author Kazuki Shimizu */ @Configuration @ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class }) @EnableConfigurationProperties(DataSourceProperties.class) @Import({ Registrar.class, DataSourcePoolMetadataProvidersConfiguration.class }) public class DataSourceAutoConfiguration {@Bean @ConditionalOnMissingBean public DataSourceInitializer dataSourceInitializer(DataSourceProperties properties, ApplicationContext applicationContext) { return new DataSourceInitializer(properties, applicationContext); }</span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">final</span> Log logger =<span style="color: #000000;"> LogFactory</br> .getLog(DataSourceAutoConfiguration.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">);</br>@Bean public Object dataSourceMBean(DataSource dataSource) { if (dataSource instanceof DataSourceProxy) { try { return ((DataSourceProxy) dataSource).createPool().getJmxPool(); } catch (SQLException ex) { logger.warn("Cannot expose DataSource to JMX (could not connect)"); } } return null; }</span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * Determines if the {</span><span style="color: #808080;">@code</span><span style="color: #008000;"> dataSource} being used by Spring was created from</br> * {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> EmbeddedDataSourceConfiguration}.</br> * </span><span style="color: #808080;">@param</span><span style="color: #008000;"> beanFactory the bean factory</br> * </span><span style="color: #808080;">@return</span><span style="color: #008000;"> true if the data source was auto-configured.</br> </span><span style="color: #008000;">*/</span></br> <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">boolean</span><span style="color: #000000;"> containsAutoConfiguredDataSource(</br> ConfigurableListableBeanFactory beanFactory) {</br> </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {</br> BeanDefinition beanDefinition </span>= beanFactory.getBeanDefinition("dataSource"<span style="color: #000000;">);</br> </span><span style="color: #0000ff;">return</span> EmbeddedDataSourceConfiguration.<span style="color: #0000ff;">class</span><span style="color: #000000;">.getName()</br> .equals(beanDefinition.getFactoryBeanName());</br> }</br> </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (NoSuchBeanDefinitionException ex) {</br> </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">false</span><span style="color: #000000;">;</br> }</br> }</br></br> @Conditional(EmbeddedDatabaseCondition.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> @ConditionalOnMissingBean({ DataSource.</span><span style="color: #0000ff;">class</span>, XADataSource.<span style="color: #0000ff;">class</span><span style="color: #000000;"> })</br> @Import(EmbeddedDataSourceConfiguration.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> </span><span style="color: #0000ff;">protected</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> EmbeddedDatabaseConfiguration {</br></br> }</br> @Configuration</br> @Conditional(PooledDataSourceCondition.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> @ConditionalOnMissingBean({ DataSource.</span><span style="color: #0000ff;">class</span>, XADataSource.<span style="color: #0000ff;">class</span><span style="color: #000000;"> })</br> @Import({ DataSourceConfiguration.Tomcat.</span><span style="color: #0000ff;">class</span>, DataSourceConfiguration.Hikari.<span style="color: #0000ff;">class</span><span style="color: #000000;">,</br> DataSourceConfiguration.Dbcp2.</span><span style="color: #0000ff;">class</span>, DataSourceConfiguration.Generic.<span style="color: #0000ff;">class</span><span style="color: #000000;"> })</br> </span><span style="color: #0000ff;">protected</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> PooledDataSourceConfiguration {</br></br> }</br> @Configuration</br> @ConditionalOnProperty(prefix </span>= "spring.datasource", name = "jmx-enabled"<span style="color: #000000;">)</br> @ConditionalOnClass(name </span>= "org.apache.tomcat.jdbc.pool.DataSourceProxy"<span style="color: #000000;">)</br> @Conditional(DataSourceAutoConfiguration.DataSourceAvailableCondition.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> @ConditionalOnMissingBean(name </span>= "dataSourceMBean"<span style="color: #000000;">)</br> </span><span style="color: #0000ff;">protected</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> TomcatDataSourceJmxConfiguration {</br>}</br> </span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> AnyNestedCondition} that checks that either {</span><span style="color: #808080;">@code</span><span style="color: #008000;"> spring.datasource.type}</br> * is set or {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> PooledDataSourceAvailableCondition} applies.</br> </span><span style="color: #008000;">*/</span></br> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span> PooledDataSourceCondition <span style="color: #0000ff;">extends</span><span style="color: #000000;"> AnyNestedCondition {super(ConfigurationPhase.PARSE_CONFIGURATION);
PooledDataSourceCondition() {
}@ConditionalOnProperty(prefix </span>= "spring.datasource", name = "type"<span style="color: #000000;">)</br> </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> ExplicitType {</br></br> }</br></br> @Conditional(PooledDataSourceAvailableCondition.</span><span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span><span style="color: #000000;"> PooledDataSourceAvailable {</br></br> }</br></br> }</br></br></br> </span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> Condition} to test if a supported connection pool is available.</br> </span><span style="color: #008000;">*/</span></br> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span> PooledDataSourceAvailableCondition <span style="color: #0000ff;">extends</span><span style="color: #000000;"> SpringBootCondition {</br></br> @Override</br> </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> ConditionOutcome getMatchOutcome(ConditionContext context,</br> AnnotatedTypeMetadata metadata) {</br> ConditionMessage.Builder message </span>=<span style="color: #000000;"> ConditionMessage</br> .forCondition(</span>"PooledDataSource"<span style="color: #000000;">);</br> </span><span style="color: #0000ff;">if</span> (getDataSourceClassLoader(context) != <span style="color: #0000ff;">null</span><span style="color: #000000;">) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .match(message.foundExactly(</span>"supported DataSource"<span style="color: #000000;">));</br> }</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .noMatch(message.didNotFind(</span>"supported DataSource"<span style="color: #000000;">).atAll());</br> }</br> </span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * Returns the class loader for the {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> DataSource} class. Used to ensure that</br> * the driver class can actually be loaded by the data source.</br> * </span><span style="color: #808080;">@param</span><span style="color: #008000;"> context the condition context</br> * </span><span style="color: #808080;">@return</span><span style="color: #008000;"> the class loader</br> </span><span style="color: #008000;">*/</span></br> <span style="color: #0000ff;">private</span><span style="color: #000000;"> ClassLoader getDataSourceClassLoader(ConditionContext context) {</br> Class</span><?> dataSourceClass = <span style="color: #0000ff;">new</span><span style="color: #000000;"> DataSourceBuilder(context.getClassLoader()) .findType();</br> </span><span style="color: #0000ff;">return</span> (dataSourceClass == <span style="color: #0000ff;">null</span> ? <span style="color: #0000ff;">null</span><span style="color: #000000;"> : dataSourceClass.getClassLoader());</br> }</br></br> }</br> </span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> Condition} to detect when an embedded {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> DataSource} type can be used.</br> * If a pooled {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> DataSource} is available, it will always be preferred to an</br> * {</span><span style="color: #808080;">@code</span><span style="color: #008000;"> EmbeddedDatabase}.</br> </span><span style="color: #008000;">*/</span></br> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span> EmbeddedDatabaseCondition <span style="color: #0000ff;">extends</span><span style="color: #000000;"> SpringBootCondition {</br></br> </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">final</span> SpringBootCondition pooledCondition = <span style="color: #0000ff;">new</span><span style="color: #000000;"> PooledDataSourceCondition();</br></br> @Override</br> </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {</br> ConditionMessage.Builder message </span>=<span style="color: #000000;"> ConditionMessage</br> .forCondition(</span>"EmbeddedDataSource"<span style="color: #000000;">);</br> </span><span style="color: #0000ff;">if</span> (anyMatches(context, metadata, <span style="color: #0000ff;">this</span><span style="color: #000000;">.pooledCondition)) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .noMatch(message.foundExactly(</span>"supported pooled data source"<span style="color: #000000;">));</br> }</br> EmbeddedDatabaseType type </span>=<span style="color: #000000;"> EmbeddedDatabaseConnection</br> .get(context.getClassLoader()).getType();</br> </span><span style="color: #0000ff;">if</span> (type == <span style="color: #0000ff;">null</span><span style="color: #000000;">) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .noMatch(message.didNotFind(</span>"embedded database"<span style="color: #000000;">).atAll());</br> }</br> </span><span style="color: #0000ff;">return</span> ConditionOutcome.match(message.found("embedded database"<span style="color: #000000;">).items(type));</br> }</br></br> }</br></br> </span><span style="color: #008000;">/**</span><span style="color: #008000;"></br> * {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> Condition} to detect when a {</span><span style="color: #808080;">@link</span><span style="color: #008000;"> DataSource} is available (either because * the user provided one or because one will be auto-configured).</br> </span><span style="color: #008000;">*/</span><span style="color: #000000;"></br> @Order(Ordered.LOWEST_PRECEDENCE </span>- 10<span style="color: #000000;">)</br> </span><span style="color: #0000ff;">static</span> <span style="color: #0000ff;">class</span> DataSourceAvailableCondition <span style="color: #0000ff;">extends</span><span style="color: #000000;"> SpringBootCondition {</br></br> </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">final</span> SpringBootCondition pooledCondition = <span style="color: #0000ff;">new</span><span style="color: #000000;"> PooledDataSourceCondition();</br></br> </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">final</span> SpringBootCondition embeddedCondition = <span style="color: #0000ff;">new</span><span style="color: #000000;"> EmbeddedDatabaseCondition();</br></br> @Override</br> </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> ConditionOutcome getMatchOutcome(ConditionContext context,</br> AnnotatedTypeMetadata metadata) {</br> ConditionMessage.Builder message </span>=<span style="color: #000000;"> ConditionMessage</br> .forCondition(</span>"DataSourceAvailable"<span style="color: #000000;">);</br> </span><span style="color: #0000ff;">if</span> (hasBean(context, DataSource.<span style="color: #0000ff;">class</span><span style="color: #000000;">)</br> </span>|| hasBean(context, XADataSource.<span style="color: #0000ff;">class</span><span style="color: #000000;">)) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .match(message.foundExactly(</span>"existing data source bean"<span style="color: #000000;">));</br> }</br> </span><span style="color: #0000ff;">if</span> (anyMatches(context, metadata, <span style="color: #0000ff;">this</span><span style="color: #000000;">.pooledCondition,</br> </span><span style="color: #0000ff;">this</span><span style="color: #000000;">.embeddedCondition)) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome.match(message</br> .foundExactly(</span>"existing auto-configured data source bean"<span style="color: #000000;">));</br> }</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> ConditionOutcome</br> .noMatch(message.didNotFind(</span>"any existing data source bean"<span style="color: #000000;">).atAll());</br> }</br></br> </span><span style="color: #0000ff;">private</span> <span style="color: #0000ff;">boolean</span> hasBean(ConditionContext context, Class<?><span style="color: #000000;"> type) {</br> </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> BeanFactoryUtils.beanNamesForTypeIncludingAncestors(</br> context.getBeanFactory(), type, </span><span style="color: #0000ff;">true</span>, <span style="color: #0000ff;">false</span>).length > 0<span style="color: #000000;">;</br> }</br></br> }</br></br>}
从上面看到，
1. DataSourceAutoConfiguration打上了@ConditionalOnClass({ DataSource.class, EmbeddedDatabaseType.class })标签，这意味着只有当DataSource.class和EmbeddedDatabaseType.class出现在classpath时，DataSourceAutoConfiguration内的自动配置bean才可能被注册。
2. DataSourceAutoConfiguration打上了@EnableConfigurationProperties(DataSourceProperties.class)标签，意味着application.properties中的属性和DataSourceProperties类自动绑定了。
@ConfigurationProperties(prefix = DataSourceProperties.PREFIX) public class DataSourceProperties implements BeanClassLoaderAware, EnvironmentAware, InitializingBean { public static final String PREFIX = "spring.datasource";...
...
private String driverClassName; private String url; private String username;
private String password;...
//setters and getters
}
上面的配置类中说明，在application.properties中以spring.datasource开头的属性将自动绑定到DataSourceProperties对象上。其他注解，如@ConditionalOnMissingBean, @ConditionalOnClass and @ConditionalOnProperty等，标识只要条件满足，bean definition将注册到ApplicationContext中。
参考文件：
【1】http://www.liaoxuefeng.com/article/001484212576147b1f07dc0ab9147a1a97662a0bd270c20000
【2】https://dzone.com/articles/how-springboot-autoconfiguration-magic-works