重点是SqlSessionFactory、SqlSession、Mapper、xml解析
mybatis:
type-aliases-package: com.cmb.test.entity
mapper-locations: classpath:mybatis/*Mapper.xml
从我们的老朋友xxAutoConfiguration开始，这次是MybatisAutoConfiguration
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
SqlSessionFactoryBean factory = new SqlSessionFactoryBean();
// 设置数据源，HikariDataSource
factory.setDataSource(dataSource);
// SpringBootVFS，作用是类扫描
factory.setVfs(SpringBootVFS.class);
// yaml文件是否配置了configLocation
if (StringUtils.hasText(this.properties.getConfigLocation())) {
factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
}
// 如果在yaml配置了mybatis.configuration.xxxx属性，这里configuration就不会为，否则为空
// 为空会new一个默认的Configuraiton，自带一些默认的属性
Configuration configuration = this.properties.getConfiguration();
if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
configuration = new Configuration();
}
if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
customizer.customize(configuration);
}
}
factory.setConfiguration(configuration);
if (this.properties.getConfigurationProperties() != null) {
factory.setConfigurationProperties(this.properties.getConfigurationProperties());
}
if (!ObjectUtils.isEmpty(this.interceptors)) {
factory.setPlugins(this.interceptors);
}
if (this.databaseIdProvider != null) {
factory.setDatabaseIdProvider(this.databaseIdProvider);
}
// 实体类所在的包
if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
}
// typeHandler，类型转换器，比如Date和时间戳的转换。定义之后可以在mapper.xml中指定typeHandler
if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
}
// 配置的mapper.xml
if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
factory.setMapperLocations(this.properties.resolveMapperLocations());
}
return factory.getObject();
}
factory.getObject()
@Override
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
@Override
public void afterPropertiesSet() throws Exception {
notNull(dataSource, "Property 'dataSource' is required");
notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),
"Property 'configuration' and 'configLocation' can not specified with together");
this.sqlSessionFactory = buildSqlSessionFactory();
}
buildSqlSessionFactory();
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
Configuration configuration;
XMLConfigBuilder xmlConfigBuilder = null;
if (this.configuration != null) {
configuration = this.configuration;
// 是否配置了variables，暂时不知道有什么用
if (configuration.getVariables() == null) {
configuration.setVariables(this.configurationProperties);
} else if (this.configurationProperties != null) {
configuration.getVariables().putAll(this.configurationProperties);
}
// 如果在yaml中配置了configLocation，就会去解析xml文件
} 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);
}
}
// 为空
if (this.objectFactory != null) {
configuration.setObjectFactory(this.objectFactory);
}
// 为空
if (this.objectWrapperFactory != null) {
configuration.setObjectWrapperFactory(this.objectWrapperFactory);
}
// SpringBootVFS，在扫描typeAliasPakeage时会用到
if (this.vfs != null) {
configuration.setVfsImpl(this.vfs);
}
// 注册别名
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 + "'");
}
}
}
// 加载自定义的拦截器
if (!isEmpty(this.plugins)) {
for (Interceptor plugin : this.plugins) {
configuration.addInterceptor(plugin);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered plugin: '" + plugin + "'");
}
}
}
// 定义自己的类型转换器，比如mybatis.type-handlers-package=com.cmb.test.handler
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 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 {
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();
}
}
// 看到事务了
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 {
// 这里是解析mapper.xml文件，将每一个select/update/insert/delete节点都解析成一个MappedStatement，包括了需要执行的sql、输入参数类型、输出参数类型等。
// MappedStatement的id是namespace加上select/update/insert/delete节点的id，正好对应包名+类名+方法名
// 所有的MapperStatement都会保存在Configuration中的mappedStatements，是一个Map，在后续sql执行过程中会用到
// 同时会在configuration中的mapperRegistry中增加对应mapper类型的MapperProxyFactory，在最后生成mapper代理时会用到
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");
}
}
// 返回一个DefaultSqlSessionFactory
return this.sqlSessionFactoryBuilder.build(configuration);
}
MybatisAutoConfiguration中也加载了SqlSessionTemplate，SqlSessionTemplate实现了SqlSession
@Bean
@ConditionalOnMissingBean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
ExecutorType executorType = this.properties.getExecutorType();
if (executorType != null) {
return new SqlSessionTemplate(sqlSessionFactory, executorType);
} else {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
ExecutorType有三种，
simple：普通类型的执行器
reuse：会重用预编译语句
batch：会重用预编译语句，而且可以批量执行
如果我们不指定，默认就是simple
mapper的加载
mapper接口的扫描有2种方式，和我们的写法有关
第一种是在启动类上加上@MapperScan注解，指定mapper所在的包
第二种是不用MapperScan，在mapper接口上用@Mapper注解标注
不过最终扫描mapper干活的都是同一批人，ClassPathMapperScanner
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MapperScannerRegistrar.class)
public @interface MapperScan {
MapperScan注解Import了MapperScannerRegistrar，MapperScannerRegistrar实现了ImportBeanDefinitionRegistrar，在启动过程中会调用registerBeanDefinitions
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
// 获取我们启动类上的MapperScan注解
AnnotationAttributes annoAttrs = AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
// this check is needed in Spring 3.1
if (resourceLoader != null) {
scanner.setResourceLoader(resourceLoader);
}
Class annotationClass = annoAttrs.getClass("annotationClass");
if (!Annotation.class.equals(annotationClass)) {
scanner.setAnnotationClass(annotationClass);
}
Class markerInterface = annoAttrs.getClass("markerInterface");
if (!Class.class.equals(markerInterface)) {
scanner.setMarkerInterface(markerInterface);
}
Class generatorClass = annoAttrs.getClass("nameGenerator");
if (!BeanNameGenerator.class.equals(generatorClass)) {
scanner.setBeanNameGenerator(BeanUtils.instantiateClass(generatorClass));
}
Class mapperFactoryBeanClass = annoAttrs.getClass("factoryBean");
if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) {
scanner.setMapperFactoryBean(BeanUtils.instantiateClass(mapperFactoryBeanClass));
}
scanner.setSqlSessionTemplateBeanName(annoAttrs.getString("sqlSessionTemplateRef"));
scanner.setSqlSessionFactoryBeanName(annoAttrs.getString("sqlSessionFactoryRef"));
// 对应MapperScan注解的value
List basePackages = new ArrayList();
for (String pkg : annoAttrs.getStringArray("value")) {
if (StringUtils.hasText(pkg)) {
basePackages.add(pkg);
}
}
for (String pkg : annoAttrs.getStringArray("basePackages")) {
if (StringUtils.hasText(pkg)) {
basePackages.add(pkg);
}
}
for (Class clazz : annoAttrs.getClassArray("basePackageClasses")) {
basePackages.add(ClassUtils.getPackageName(clazz));
}
// 注册过滤器
scanner.registerFilters();
// 包扫描
scanner.doScan(StringUtils.toStringArray(basePackages));
}
org.mybatis.spring.mapper.ClassPathMapperScanner#registerFilters
public void registerFilters() {
boolean acceptAllInterfaces = true;
// 指定需要扫描的注解是@Mapper
// if specified, use the given annotation and / or marker interface
if (this.annotationClass != null) {
addIncludeFilter(new AnnotationTypeFilter(this.annotationClass));
acceptAllInterfaces = false;
}
// 对特定接口的处理
// override AssignableTypeFilter to ignore matches on the actual marker interface
if (this.markerInterface != null) {
addIncludeFilter(new AssignableTypeFilter(this.markerInterface) {
@Override
protected boolean matchClassName(String className) {
return false;
}
});
acceptAllInterfaces = false;
}
// acceptAllInterfaces，为true的话所有的接口都会被加进来
if (acceptAllInterfaces) {
// default include filter that accepts all classes
addIncludeFilter(new TypeFilter() {
@Override
public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
return true;
}
});
}
// 排除package-info结尾的接口
// exclude package-info.java
addExcludeFilter(new TypeFilter() {
@Override
public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
String className = metadataReader.getClassMetadata().getClassName();
return className.endsWith("package-info");
}
});
}
org.mybatis.spring.mapper.ClassPathMapperScanner#doScan
@Override
public Set doScan(String... basePackages) {
// 扫描mapper接口的逻辑
Set beanDefinitions = super.doScan(basePackages);
if (beanDefinitions.isEmpty()) {
logger.warn("No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration.");
} else {
// 这里有一句话很重要definition.setBeanClass(this.mapperFactoryBean.getClass());
processBeanDefinitions(beanDefinitions);
}
return beanDefinitions;
}
// mapperFactoryBean是一个FactoryBean，在Spring初始化的过程中，getBean会触发FactoryBean的getObject方法（以后有时间再看）
org.mybatis.spring.mapper.MapperFactoryBean#getObject
@Override
public T getObject() throws Exception {
// 这里是sqlSession是DefaultSqlSession
return getSqlSession().getMapper(this.mapperInterface);
}
// org.apache.ibatis.session.defaults.DefaultSqlSession#getMapper
@Override
public T getMapper(Class type) {
return configuration.getMapper(type, this);
}
// org.apache.ibatis.session.Configuration#getMapper
public T getMapper(Class type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
// org.apache.ibatis.binding.MapperRegistry#getMapper
public T getMapper(Class type, SqlSession sqlSession) {
final MapperProxyFactory mapperProxyFactory = (MapperProxyFactory) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
org.apache.ibatis.binding.MapperProxyFactory#newInstance
(org.apache.ibatis.session.SqlSession)
public T newInstance(SqlSession sqlSession) {
// 所以最后在service层中操作的mapper对象，就是MapperProxy类型的一个jdk代理
final MapperProxy mapperProxy = new MapperProxy(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
@SuppressWarnings("unchecked")
protected T newInstance(MapperProxy mapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}