深入浅出重构Mybatis与Spring集成的SqlSessionFactoryBean（上）

<bean id="sqlSessionFactory" p:dataSource-ref="dataSource" class="org.mybatis.spring.SqlSessionFactoryBean" p:configLocation="classpath:mybatis/mybatis-config.xml"><property name="mapperLocations"><array><value>classpath*:**/*.sqlmapper.xml</value></array></property></bean>

SqlSessionFactoryBean的作用是产生SqlSessionFactory，那我们看一下这个方法(SqlSessionFactoryBean.java 384-538行)：/*** Build a {@code SqlSessionFactory} instance.** The default implementation uses the standard MyBatis {@code XMLConfigBuilder} API to build a* {@code SqlSessionFactory} instance based on an Reader.* Since 1.3.0, it can be specified a {@link Configuration} instance directly(without config file).** @return SqlSessionFactory* @throws IOException if loading the config file failed*/protected SqlSessionFactory buildSqlSessionFactory() throws IOException {Configuration configuration;XMLConfigBuilder xmlConfigBuilder = null;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(), 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();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);}if (hasLength(this.typeAliasesPackage)) {String[] typeAliasPackageArray = tokenizeToStringArray(this.typeAliasesPackage,ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);for (String packageToScan : typeAliasPackageArray) {configuration.getTypeAliasRegistry().registerAliases(packageToScan,typeAliasesSuperType == null ? Object.class : typeAliasesSuperType);if (LOGGER.isDebugEnabled()) {LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases");}}}if (!isEmpty(this.typeAliases)) {for (Class<?> typeAlias : this.typeAliases) {configuration.getTypeAliasRegistry().registerAlias(typeAlias);if (LOGGER.isDebugEnabled()) {LOGGER.debug("Registered type alias: '" + typeAlias + "'");}}}if (!isEmpty(this.plugins)) {for (Interceptor plugin : this.plugins) {configuration.addInterceptor(plugin);if (LOGGER.isDebugEnabled()) {LOGGER.debug("Registered plugin: '" + plugin + "'");}}}if (hasLength(this.typeHandlersPackage)) {String[] typeHandlersPackageArray = tokenizeToStringArray(this.typeHandlersPackage,ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);for (String packageToScan : typeHandlersPackageArray) {configuration.getTypeHandlerRegistry().register(packageToScan);if (LOGGER.isDebugEnabled()) {LOGGER.debug("Scanned package: '" + packageToScan + "' for type handlers");}}}if (!isEmpty(this.typeHandlers)) {for (TypeHandler<?> typeHandler : this.typeHandlers) {configuration.getTypeHandlerRegistry().register(typeHandler);if (LOGGER.isDebugEnabled()) {LOGGER.debug("Registered type handler: '" + typeHandler + "'");}}}if (this.databaseIdProvider != null) {//fix #64 set databaseId before parse mapper xmlstry {configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource));} catch (SQLException e) {throw new NestedIOException("Failed getting a databaseId", e);}}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 ex) {throw new NestedIOException("Failed to parse config resource: " + this.configLocation, ex);} finally {ErrorContext.instance().reset();}}if (this.transactionFactory == null) {this.transactionFactory = new SpringManagedTransactionFactory();}configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource));if (!isEmpty(this.mapperLocations)) {for (Resource mapperLocation : this.mapperLocations) {if (mapperLocation == null) {continue;}try {XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),configuration, mapperLocation.toString(), configuration.getSqlFragments());xmlMapperBuilder.parse();} catch (Exception e) {throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);} 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);}

<!-- DTD方式 --><?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="org.dysd.dao.mybatis.config.IExampleDao"></mapper><!-- SCHEMA方式 --><?xml version="1.0" encoding="UTF-8" ?><mapper xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://dysd.org/schema/sqlmapper"xsi:schemaLocation="http://dysd.org/schema/sqlmapper http://dysd.org/schema/sqlmapper.xsd"namespace="org.dysd.dao.mybatis.config.IExampleDao"></mapper>

<!--简化前--><select id="select" resultType="map">SELECT * FROM TABLE_NAME WHERE FIELD1 = #{field1, jdbcType=VARCHAR} </select><!--简化后--><select id="select">SELECT * FROM TABLE_NAME WHERE FIELD1 = #{field1, jdbcType=VARCHAR} </select>