一、@MapperScan(basePackages = { "com.uenpay.wfb.repository" })
MapperScan注解中有 @Import(MapperScannerRegistrar.class)，MapperScannerRegistrar实现了接口ImportBeanDefinitionRegistrar。
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通过MapperScannerRegistrar执行registerBeanDefinitions方法，扫描basePackages路径下的包，并把对应的mapper接口注入到spring的初始容器BeanDefinition，不过需要注意的是，这些接口的BeanDefinition的属性beanClass是 org.mybatis.spring.mapper.MapperFactoryBean
这一阶段就完成了mapper接口的初始注入
二、配置类 MybatisAutoConfiguration
- mybatis-spring-boot-autoconfigure 包里有一个配置文件spring.factories里面包含配置类 MybatisAutoConfiguration
- springboot由于自动装配原理，会自动加载mybatis的配置类 MybatisAutoConfiguration，配置类中会完成@Bean注解的实例化，并且创建了SqlSessionFactoryBean对象，SqlSessionFactoryBean是实现了FactoryBean接口的，下面执行了factory.getObject()方法
@Override
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
- afterPropertiesSet()方法中会执行buildSqlSessionFactory（）
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();
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);
}
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 (ClasstypeAlias : 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 (TypeHandlertypeHandler : 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 xmls
try {
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 {
// 解析mybatis-config.xml配置
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 {
// 解析 Mapper.xml文件，并封装成MappedStatement对象保存到Configuration
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);
}
三、SqlSessionFactory
- SqlSessionFactory 初始化过程包括： SqlSessionFactoryBean 的加载 及 执行 他的 getObject()方法，该方法的主要逻辑功能时加载 mybatis的配置类 mybatis-config.xml 和 一些mapper.xml文件
- 加载 mapper.xml 解析一些标签和sql语句 并封装成 MappedStatement 对象放到 Configuration的map集合中，其中key是mapper.xml文件中增删改查标签中的id
四、生成代理Bean
在生成mapper bean实例时，和其他Bean实例方式差不多，只不过应为mapper是接口，而他的beanClass属性是 org.mybatis.spring.mapper.MapperFactoryBean,所以对于其他常规bean还是有区别的，他会走FactoryBean的路线，通过factoryBean.getObject()返回代理对象，这里用到的是JDK动态代理，生成后填充到spring容器中。
代理几个关键的类
public class MapperProxyFactory{
private final ClassmapperInterface;
private final MapmethodCache = new ConcurrentHashMap();
public MapperProxyFactory(ClassmapperInterface) {
this.mapperInterface = mapperInterface;
}
public ClassgetMapperInterface() {
return mapperInterface;
}
public MapgetMethodCache() {
return methodCache;
}
@SuppressWarnings("unchecked")
protected T newInstance(MapperProxymapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {
final MapperProxymapperProxy = new MapperProxy(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
}
public class MapperProxyimplements InvocationHandler, Serializable {
private static final long serialVersionUID = -6424540398559729838L;
private final SqlSession sqlSession;
private final ClassmapperInterface;
private final MapmethodCache;
public MapperProxy(SqlSession sqlSession, ClassmapperInterface, MapmethodCache) {
this.sqlSession = sqlSession;
this.mapperInterface = mapperInterface;
this.methodCache = methodCache;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (Object.class.equals(method.getDeclaringClass())) {
try {
return method.invoke(this, args);
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
}
final MapperMethod mapperMethod = cachedMapperMethod(method);
return mapperMethod.execute(sqlSession, args);
}
private MapperMethod cachedMapperMethod(Method method) {
MapperMethod mapperMethod = methodCache.get(method);
if (mapperMethod == null) {
mapperMethod = new MapperMethod(mapperInterface, method, sqlSession.getConfiguration());
methodCache.put(method, mapperMethod);
}
return mapperMethod;
}
}
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