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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。
sqlSessionFactory创建
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：
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。
代码语言：javascript复制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。
代码语言：javascript复制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, ",; tn");
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, ",; tn");
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：
代码语言：javascript复制 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。
代码语言：javascript复制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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