sqlSessionFactory创建

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前言

分析上篇文章的整合的配置文件，我们可以知道配置的bean是成树状结构的，而在树的最顶层是类型为org.mybatis.Spring.SqlSessionFactoryBean的bean，它将其他相关的bean组装在了一起，那么我们的分析就从此类开始。

对于配置文件的读取，Spring是通过org.mybatis.Spring.SqlSessionFactoryBean封装了MyBatis中的实现。首先来看一下这个类的类图：

sqlSessionFactory创建

根据上图对两个感兴趣的接口FactoryBean和InitializingBean。

　　❤ InitializingBean：实现此接口的bean会在初始化时调用其afterPropertiesSet方法来进行bean的逻辑初始化。

　　❤ FactoryBean：一旦某个bean实现此接口，那么通过getBean方法获取bean时其实是获取此类的getObject返回的实例。

1.sqlSessionFactoryBean的初始化

查看org.mybatis.Spring.SqlSessionFactoryBean类型的bean在初始化时做了哪些逻辑实现。

public void afterPropertiesSet() throws Exception {
        Assert.notNull(this.dataSource, "Property 'dataSource' is required");
        Assert.notNull(this.sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
        Assert.state(this.configuration == null && this.configLocation == null || this.configuration == null || this.configLocation == null, "Property 'configuration' and 'configLocation' can not specified with together");
        this.sqlSessionFactory = this.buildSqlSessionFactory();
    }

很显然，此函数的主要目的是对于sqlSessionFactory的初始化，sqlSessionFactory是所有MyBatis功能的基础。

protected SqlSessionFactory buildSqlSessionFactory() throws IOException { XMLConfigBuilder xmlConfigBuilder = null; Configuration configuration; if (this.configuration != null) { configuration = this.configuration; if (configuration.getVariables() == null) { configuration.setVariables(this.configurationProperties); } else if (this.configurationProperties != null) { configuration.getVariables().putAll(this.configurationProperties); } } else if (this.configLocation != null) { xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), (String)null, this.configurationProperties); configuration = xmlConfigBuilder.getConfiguration(); } else { if (LOGGER.isDebugEnabled()) { LOGGER.debug("Property 'configuration' or 'configLocation' not specified, using default MyBatis Configuration"); } configuration = new Configuration(); if (this.configurationProperties != null) { configuration.setVariables(this.configurationProperties); } } if (this.objectFactory != null) { configuration.setObjectFactory(this.objectFactory); } if (this.objectWrapperFactory != null) { configuration.setObjectWrapperFactory(this.objectWrapperFactory); } if (this.vfs != null) { configuration.setVfsImpl(this.vfs); } String[] typeHandlersPackageArray; String[] var4; int var5; int var6; String packageToScan; if (StringUtils.hasLength(this.typeAliasesPackage)) { typeHandlersPackageArray = StringUtils.tokenizeToStringArray(this.typeAliasesPackage, ",; \t\n"); var4 = typeHandlersPackageArray; var5 = typeHandlersPackageArray.length; for(var6 = 0; var6 < var5; ++var6) { packageToScan = var4[var6]; configuration.getTypeAliasRegistry().registerAliases(packageToScan, this.typeAliasesSuperType == null ? Object.class : this.typeAliasesSuperType); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases"); } } } int var27; if (!ObjectUtils.isEmpty(this.typeAliases)) { Class[] var25 = this.typeAliases; var27 = var25.length; for(var5 = 0; var5 < var27; ++var5) { Class<?> typeAlias = var25[var5]; configuration.getTypeAliasRegistry().registerAlias(typeAlias); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Registered type alias: '" + typeAlias + "'"); } } } if (!ObjectUtils.isEmpty(this.plugins)) { Interceptor[] var26 = this.plugins; var27 = var26.length; for(var5 = 0; var5 < var27; ++var5) { Interceptor plugin = var26[var5]; configuration.addInterceptor(plugin); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Registered plugin: '" + plugin + "'"); } } } if (StringUtils.hasLength(this.typeHandlersPackage)) { typeHandlersPackageArray = StringUtils.tokenizeToStringArray(this.typeHandlersPackage, ",; \t\n"); var4 = typeHandlersPackageArray; var5 = typeHandlersPackageArray.length; for(var6 = 0; var6 < var5; ++var6) { packageToScan = var4[var6]; configuration.getTypeHandlerRegistry().register(packageToScan); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Scanned package: '" + packageToScan + "' for type handlers"); } } } if (!ObjectUtils.isEmpty(this.typeHandlers)) { TypeHandler[] var28 = this.typeHandlers; var27 = var28.length; for(var5 = 0; var5 < var27; ++var5) { TypeHandler<?> typeHandler = var28[var5]; configuration.getTypeHandlerRegistry().register(typeHandler); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Registered type handler: '" + typeHandler + "'"); } } } if (this.databaseIdProvider != null) { try { configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource)); } catch (SQLException var24) { throw new NestedIOException("Failed getting a databaseId", var24); } } if (this.cache != null) { configuration.addCache(this.cache); } if (xmlConfigBuilder != null) { try { xmlConfigBuilder.parse(); if (LOGGER.isDebugEnabled()) { LOGGER.debug("Parsed configuration file: '" + this.configLocation + "'"); } } catch (Exception var22) { throw new NestedIOException("Failed to parse config resource: " + this.configLocation, var22); } finally { ErrorContext.instance().reset(); } } if (this.transactionFactory == null) { this.transactionFactory = new SpringManagedTransactionFactory(); } configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource)); if (!ObjectUtils.isEmpty(this.mapperLocations)) { Resource[] var29 = this.mapperLocations; var27 = var29.length; for(var5 = 0; var5 < var27; ++var5) { Resource mapperLocation = var29[var5]; if (mapperLocation != null) { try { XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(), configuration, mapperLocation.toString(), configuration.getSqlFragments()); xmlMapperBuilder.parse(); } catch (Exception var20) { throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", var20); } finally { ErrorContext.instance().reset(); } if (LOGGER.isDebugEnabled()) { LOGGER.debug("Parsed mapper file: '" + mapperLocation + "'"); } } } } else if (LOGGER.isDebugEnabled()) { LOGGER.debug("Property 'mapperLocations' was not specified or no matching resources found"); } return this.sqlSessionFactoryBuilder.build(configuration); }

从函数中可以看到，尽管我们还是习惯于将MyBatis的配置和Spring的配置独立出来，但是，这并不代表Spring中的配置不支持直接配置。也就是说，在上篇文章的示例中，完全裤取消配置中的configLocation属性，而把其中的属性直接写在sqlSessionFactoryBean中。

从这个函数中还可以得知，配置文件还可以支持其他多种属性的配置，如configLocation、objectFactory、objectWrapperFactory、typeAliasesPackage、typeAliases、typeHandlersPackage、plugins、typeHandlers、transactionFactory、databaseIdProvider、mapperLocations。

其实，如果只按照常用的配置，那么我们只需要在函数最开始按照如下方式处理configLocation：

　　 xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(),null,this.configurationProperties); configuration = xmlConfigBuilder.getConfiguration();

根据configLocation构造XMLConfigBuilder并进行解析，但是，为了体现Spring更强大的兼容性，Spring还整合了MyBatis中其他属性的注入，并通过实例configuration来承载每一步所获取的信息并最终使用sqlSessionFactoryBuilder实例根据解析到的configuration创建sqlSessionFactory实例。

2.获取SqlSessionFactoryBean实例

由于sqlSessionFactoryBean实现了FactoryBean接口，所以当通过getBean方法获取对应实例时，其实是获取该类的getObject函数返回的实例，也就是获得初始化后的sqlSessionFactory属性。

public SqlSessionFactory getObject() throws Exception { if (this.sqlSessionFactory == null) { this.afterPropertiesSet(); } return this.sqlSessionFactory; }

参考：《Spring源码深度解析》郝佳编著：

转载于:https://www.cnblogs.com/Joe-Go/p/10255301.html

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sqlSessionFactory创建

前言