背景:項目中需要對數據庫的寫操作進行攔截。使用Mybatis的plugins可以完整這個操作
之前使用Spring+mybatis時只需要在xml中SqlSessionFactoryBean中進行配置。其中配置文件信息和插件代碼
<property name="plugins">
<array>
<bean class="com.meituan.service.movie.emember.web.DataSourceStopWritePlugin"/>
</array>
</property>
// ExamplePlugin.java
@Intercepts({@Signature(
type= Executor.class,
method = "update",
args = {MappedStatement.class,Object.class})})
public class ExamplePlugin implements Interceptor {
public Object intercept(Invocation invocation) throws Throwable {
return invocation.proceed();
}
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
public void setProperties(Properties properties) {
}
}
而在使用SpringBoot時,由於SqlSessionFactoryBean是在MybatisAutoConfiguration中初始化SqlSessionFactory時配置的,而不是作爲bean進行注入。所以我們的代碼中沒有辦法拿到SqlSessionFactoryBean實例對其設置plugins。在查閱了相關用法得知我們只需要將上面的ExamplePlugin實例交給Spring管理就可以自動設置到SqlSessionFactoryBean中。因此只需要在ExamplePlugin類的註解上加上@component註解即可。
背後原理:
查看MybatisAutoConfiguration關於配置sqlSessionFactory的源碼
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
factory.setDataSource(dataSource);
factory.setVfs(SpringBootVFS.class);
if (StringUtils.hasText(this.properties.getConfigLocation())) {
factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
}
Configuration configuration = this.properties.getConfiguration();
if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
configuration = new Configuration();
}
if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
customizer.customize(configuration);
}
}
factory.setConfiguration(configuration);
if (this.properties.getConfigurationProperties() != null) {
factory.setConfigurationProperties(this.properties.getConfigurationProperties());
}
if (!ObjectUtils.isEmpty(this.interceptors)) {
factory.setPlugins(this.interceptors);
}
if (this.databaseIdProvider != null) {
factory.setDatabaseIdProvider(this.databaseIdProvider);
}
if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
}
if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
}
if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
factory.setMapperLocations(this.properties.resolveMapperLocations());
}
return factory.getObject();
}
代碼中
if (!ObjectUtils.isEmpty(this.interceptors)) {
factory.setPlugins(this.interceptors);
}
是對插件的設置。這裏的interceptors是在配置類初始化時通過interceptorsProvider獲取。
public MybatisAutoConfiguration(MybatisProperties properties,
ObjectProvider<Interceptor[]> interceptorsProvider,
ResourceLoader resourceLoader,
ObjectProvider<DatabaseIdProvider> databaseIdProvider,
ObjectProvider<List<ConfigurationCustomizer>> configurationCustomizersProvider) {
this.properties = properties;
this.interceptors = interceptorsProvider.getIfAvailable();
this.resourceLoader = resourceLoader;
this.databaseIdProvider = databaseIdProvider.getIfAvailable();
this.configurationCustomizers = configurationCustomizersProvider.getIfAvailable();
}
interceptorsProvider是ObjectProvider類型,interceptorsProvider.getIfAvailable()的意思就是獲取beanFactory中所有的Interceptor實例。
關於ObjectProvider的解讀可參考下面兩篇文章:
https://spring.io/blog/2016/03/04/core-container-refinements-in-spring-framework-4-3
https://blog.csdn.net/alex_xfboy/article/details/83342164