使用过SSM的框架的都知道mybatis这个持久层框架&＃xff0c;今天小编就来简单说说这个框架的核心工厂类sqlSessionFactory的加载过程&＃xff0c;一般的SSM框架我们都会在spring的application.xml中引入如下的配置&＃xff1a;
其中的SqlSessionFactoryBean便是加载sqlSessionFactory的入口&＃xff0c;首先我们来看看这个类的源代码&＃xff1a;
public class SqlSessionFactoryBean implements FactoryBean, InitializingBean, ApplicationListener {
private static final Log logger &＃61; LogFactory.getLog(SqlSessionFactoryBean.class);
private Resource configLocation;
private Resource[] mapperLocations;
private DataSource dataSource;
private TransactionFactory transactionFactory;
private Properties configurationProperties;
private SqlSessionFactoryBuilder sqlSessionFactoryBuilder &＃61; new SqlSessionFactoryBuilder();
private SqlSessionFactory sqlSessionFactory;
其中标红的两处&＃xff0c;就是我们在application.xml中注入的两个属性&＃xff0c;从源码中我们可以看出该类实现了InitializingBean接口&＃xff0c;实现了其afterPropertiesSet()方法&＃xff0c;
该方法是在当前bean的所有属性被初始化完成之后再执行&＃xff0c;也就是其中的datasource和configurationProperties等属性&＃xff0c;接下来我们看看这个方法主要干什么了&＃xff1f;
public void afterPropertiesSet() throws Exception {
notNull(dataSource, "Property &＃39;dataSource&＃39; is required");
notNull(sqlSessionFactoryBuilder, "Property &＃39;sqlSessionFactoryBuilder&＃39; is required");
this.sqlSessionFactory &＃61; buildSqlSessionFactory();
}
其中第5行很明显的buildSqlSessionFactory()方法初始化了sqlSessionFactory &＃xff0c;接下来我们看看这个方法的主要行为&＃xff1a;
Configuration configuration;
XMLConfigBuilder xmlConfigBuilder &＃61; null;
if (this.configLocation !&＃61; null) {
xmlConfigBuilder &＃61; new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
configuration &＃61; xmlConfigBuilder.getConfiguration();
} else {
if (logger.isDebugEnabled()) {
logger.debug("Property &＃39;configLocation&＃39; not specified, using default MyBatis Configuration");
}
configuration &＃61; new Configuration();
configuration.setVariables(this.configurationProperties);
}
if (this.objectFactory !&＃61; null) {
configuration.setObjectFactory(this.objectFactory);
}
if (this.objectWrapperFactory !&＃61; null) {
configuration.setObjectWrapperFactory(this.objectWrapperFactory);
}
if (hasLength(this.typeAliasesPackage)) {
String[] typeAliasPackageArray &＃61; tokenizeToStringArray(this.typeAliasesPackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
for (String packageToScan : typeAliasPackageArray) {
configuration.getTypeAliasRegistry().registerAliases(packageToScan,
typeAliasesSuperType &＃61;&＃61; null ? Object.class : typeAliasesSuperType);
if (logger.isDebugEnabled()) {
logger.debug("Scanned package: &＃39;" &＃43; packageToScan &＃43; "&＃39; for aliases");
}
}
}
if (!isEmpty(this.typeAliases)) {
for (Class> typeAlias : this.typeAliases) {
configuration.getTypeAliasRegistry().registerAlias(typeAlias);
if (logger.isDebugEnabled()) {
logger.debug("Registered type alias: &＃39;" &＃43; typeAlias &＃43; "&＃39;");
}
}
}
if (!isEmpty(this.plugins)) {
for (Interceptor plugin : this.plugins) {
configuration.addInterceptor(plugin);
if (logger.isDebugEnabled()) {
logger.debug("Registered plugin: &＃39;" &＃43; plugin &＃43; "&＃39;");
}
}
}
if (hasLength(this.typeHandlersPackage)) {
String[] typeHandlersPackageArray &＃61; tokenizeToStringArray(this.typeHandlersPackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
for (String packageToScan : typeHandlersPackageArray) {
configuration.getTypeHandlerRegistry().register(packageToScan);
if (logger.isDebugEnabled()) {
logger.debug("Scanned package: &＃39;" &＃43; packageToScan &＃43; "&＃39; for type handlers");
}
}
}
if (!isEmpty(this.typeHandlers)) {
for (TypeHandler> typeHandler : this.typeHandlers) {
configuration.getTypeHandlerRegistry().register(typeHandler);
if (logger.isDebugEnabled()) {
logger.debug("Registered type handler: &＃39;" &＃43; typeHandler &＃43; "&＃39;");
}
}
}
if (xmlConfigBuilder !&＃61; null) {
try {
xmlConfigBuilder.parse();
if (logger.isDebugEnabled()) {
logger.debug("Parsed configuration file: &＃39;" &＃43; this.configLocation &＃43; "&＃39;");
}
} catch (Exception ex) {
throw new NestedIOException("Failed to parse config resource: " &＃43; this.configLocation, ex);
} finally {
ErrorContext.instance().reset();
}
}
if (this.transactionFactory &＃61;&＃61; null) {
this.transactionFactory &＃61; new SpringManagedTransactionFactory();
}
Environment environment &＃61; new Environment(this.environment, this.transactionFactory, this.dataSource);
configuration.setEnvironment(environment);
if (this.databaseIdProvider !&＃61; null) {
try {
configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource));
} catch (SQLException e) {
throw new NestedIOException("Failed getting a databaseId", e);
}
}
if (!isEmpty(this.mapperLocations)) {
for (Resource mapperLocation : this.mapperLocations) {
if (mapperLocation &＃61;&＃61; null) {
continue;
}
try {
XMLMapperBuilder xmlMapperBuilder &＃61; new XMLMapperBuilder(mapperLocation.getInputStream(),
configuration, mapperLocation.toString(), configuration.getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception e) {
throw new NestedIOException("Failed to parse mapping resource: &＃39;" &＃43; mapperLocation &＃43; "&＃39;", e);
} finally {
ErrorContext.instance().reset();
}
if (logger.isDebugEnabled()) {
logger.debug("Parsed mapper file: &＃39;" &＃43; mapperLocation &＃43; "&＃39;");
}
}
} else {
if (logger.isDebugEnabled()) {
logger.debug("Property &＃39;mapperLocations&＃39; was not specified or no matching resources found");
}
}
该方法主要就是设置configuration参数&＃xff0c;首先是从mybatis-config.xml中获取对应的配置信息&＃xff0c;然后再从spring的注入属性中获取所有的配置信息&＃xff0c;从后调用
sqlSessionFactoryBuilder.build(configuration)方法获取sqlSessionFactory的实例。
由于整个加载过程没有过多的难点&＃xff0c;所以就介绍到这里&＃xff0c;感兴趣的朋友可以自己去源码&＃xff0c;了解更多知识。
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