参考mybatis进阶4——与Spring的集成
1.SqlSessionFactoryBean
public class SqlSessionFactoryBean implements FactoryBean, InitializingBean, ApplicationListener {
实现FactoryBean接口的getObject方法：
/**
*
* 将SqlSessionFactory对象注入spring容器
* {@inheritDoc}
*/
@Override
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
SqlSessionFactoryBean实现InitializingBean接口，需要实现其afterPropertiesSet()：
@Override
//在spring容器中创建全局唯一的sqlSessionFactory
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();
}
核心是buildSqlSessionFactory：
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
Configuration configuration;
XMLConfigBuilder xmlConfigBuilder = null;
if (this.configuration != null) {//如果configuration不为空，则使用该对象，并对其进行配置
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) {//创建xmlConfigBuilder，读取mybatis的核心配置文件
xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
configuration = xmlConfigBuilder.getConfiguration();
} else {//如果configuration为空，实例化一个configuration对象
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);
}
}
//设置objectFactory
if (this.objectFactory != null) {
configuration.setObjectFactory(this.objectFactory);
}
//设置objectWrapperFactory
if (this.objectWrapperFactory != null) {
configuration.setObjectWrapperFactory(this.objectWrapperFactory);
}
//设置vfs
if (this.vfs != null) {
configuration.setVfsImpl(this.vfs);
}
//扫描指定的包typeAliasesPackage，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");
}
}
}
//为typeAliases指定的类注册别名
if (!isEmpty(this.typeAliases)) {
for (Class typeAlias : this.typeAliases) {
configuration.getTypeAliasRegistry().registerAlias(typeAlias);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered type alias: '" + typeAlias + "'");
}
}
}
//注册插件
if (!isEmpty(this.plugins)) {
for (Interceptor plugin : this.plugins) {
configuration.addInterceptor(plugin);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered plugin: '" + plugin + "'");
}
}
}
//扫描指定的包typeHandlersPackage，注册类型解析器
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");
}
}
}
//为typeHandlers指定的类注册类型解析器
if (!isEmpty(this.typeHandlers)) {
for (TypeHandler typeHandler : this.typeHandlers) {
configuration.getTypeHandlerRegistry().register(typeHandler);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Registered type handler: '" + typeHandler + "'");
}
}
}
//配置databaseIdProvider
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);
}
}
//配置缓存
if (this.cache != null) {
configuration.addCache(this.cache);
}
//使用xmlConfigBuilder读取mybatis的核心配置文件
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();
}
}
//默认使用SpringManagedTransactionFactory作为事务管理器
if (this.transactionFactory == null) {
this.transactionFactory = new SpringManagedTransactionFactory();
}
//设置Environment
configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource));
//根据mapperLocations的配置，处理映射配置文件以及相应的mapper接口
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");
}
}
//最终使用sqlSessionFactoryBuilder创建sqlSessionFactory
return this.sqlSessionFactoryBuilder.build(configuration);
}
可知SqlSessionFactoryBean主要通过对applicationContext.xml解析完成时Configuration的实例化以及对完成对映射配置文件mapper*.xml的解析。
因为这个方法内有两个关键类：
*XMLConfigBuilder：在mybatis中主要负责解释mybatis-config.xml
XMLMapperBuilder：负责解析映射配置文件
2.MapperFactoryBean
2.1 MapperFactoryBean测试
applicationContext.xml配置，注入MapperFactoryBean：
UserServiceImpl.java中按名字注入tUserMapper：
@Service
public class UserServiceImpl implements UserService{
@Resource(name="tUserMapper")
private TUserMapper userMapper;
@Override
public TUser getUserById(Integer id) {
return userMapper.selectByPrimaryKey(id);
}
}
测试代码：
public class MybatisSpringTest {
@Resource
private UserService us;
@Test
public void TestSpringMyBatis(){
System.out.println(us.getUserById(1).toString());
}
测试结果：
TUser [id=1, userName=lison, realName=李小宇, sex=1, mobile=186995587422, [email protected], note=lison的备注, positionId=1]
2.2 MapperFactoryBean源码解析
实现FactoryBean接口的getObject方法：
/**
* 通过在容器中的mapperRegistry，返回当前mapper接口的动态代理
*
* {@inheritDoc}
*/
@Override
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
调用SqlSessionTemplate的getMapper：
@Override
public T getMapper(Class type) {
return getConfiguration().getMapper(type, this);
}
调用Configuration的getMapper：
public T getMapper(Class type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
调用MapperRegistry的getMapper：
@SuppressWarnings("unchecked")
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);
}
}
调用MapperProxyFactory的newInstance：
public T newInstance(SqlSession sqlSession) {
final MapperProxy mapperProxy = new MapperProxy(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
2.2.1 这里解决了一个重要问题
@Test
// 测试自动映射以及下划线自动转化驼峰
public void quickStart() throws IOException {
// 2.获取sqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
// 3.获取对应mapper
TUserMapper mapper = sqlSession.getMapper(TUserMapper.class);
// 4.执行查询语句并返回结果
TUser user = mapper.selectByPrimaryKey(1);
System.out.println(user.toString());
}
TUserMapper是方法级别的，而注入到Spring的容器中显然不是。
@Service
public class UserServiceImpl implements UserService{
@Resource(name="tUserMapper")
private TUserMapper userMapper;
@Override
public TUser getUserById(Integer id) {
return userMapper.selectByPrimaryKey(id);
}
}
MyBatis-Spring是通过FactoryBean来解决的，FactoryBean每次通过getObject来生成新的动态代理对象来解决这个问题，本质上与MyBatis中没有区别！
3.一种更方便的方法——MapperScannerConfigurer
MapperScannerConfigurer会将指定basePackage下面的所有接口都以MapperFactoryBean形式注册到Spring容器中。
public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {
核心实现了BeanDefinitionRegistry后置处理器BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry，主要是对bean的定义信息进行修改增强，例如对bean的类型进行转换：
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
if (this.processPropertyPlaceHolders) {//占位符处理
processPropertyPlaceHolders();
}
//实例化ClassPathMapperScanner，并对scanner相关属性进行配置
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
scanner.setAddToConfig(this.addToConfig);
scanner.setAnnotationClass(this.annotationClass);
scanner.setMarkerInterface(this.markerInterface);
scanner.setSqlSessionFactory(this.sqlSessionFactory);
scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
scanner.setResourceLoader(this.applicationContext);
scanner.setBeanNameGenerator(this.nameGenerator);
scanner.registerFilters();//根据上述配置，生成过滤器，只扫描合条件的class
//扫描指定的包以及其子包
scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
调用ClassPathBeanDefinitionScanner：
public int scan(String... basePackages) {
int beanCountAtScanStart = this.registry.getBeanDefinitionCount();
doScan(basePackages);
// Register annotation config processors, if necessary.
if (this.includeAnnotationConfig) {
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
return (this.registry.getBeanDefinitionCount() - beanCountAtScanStart);
}
调用ClassPathMapperScanner的doScan：
@Override
public Set doScan(String... basePackages) {
//通过父类的扫描，获取所有复合条件的BeanDefinitionHolder对象
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 {
//处理扫描得到的BeanDefinitionHolder集合，将集合中的每一个mapper接口转换成MapperFactoryBean后，注册至spring容器
processBeanDefinitions(beanDefinitions);
}
return beanDefinitions;
}
转换成MapperFactoryBean：
//处理扫描得到的BeanDefinitionHolder集合，将集合中的每一个mapper接口转换成MapperFactoryBean后，注册至spring容器
private void processBeanDefinitions(Set beanDefinitions) {
GenericBeanDefinition definition;
//遍历集合
for (BeanDefinitionHolder holder : beanDefinitions) {
definition = (GenericBeanDefinition) holder.getBeanDefinition();
if (logger.isDebugEnabled()) {
logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName()
+ "' and '" + definition.getBeanClassName() + "' mapperInterface");
}
// the mapper interface is the original class of the bean
// but, the actual class of the bean is MapperFactoryBean
//将添加扫描到的接口类型作为构造函数的入参
definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59
//讲bean的类型转换成mapperFactoryBean
definition.setBeanClass(this.mapperFactoryBean.getClass());
//增加addToConfig属性
definition.getPropertyValues().add("addToConfig", this.addToConfig);
boolean explicitFactoryUsed = false;
//增加sqlSessionFactory属性
if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionFactory != null) {
definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
explicitFactoryUsed = true;
}
//增加sqlSessionTemplate属性
if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
if (explicitFactoryUsed) {
logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionTemplate != null) {
if (explicitFactoryUsed) {
logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
explicitFactoryUsed = true;
}
//修改自动注入的方式 bytype
if (!explicitFactoryUsed) {
if (logger.isDebugEnabled()) {
logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
}
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}
}
}
4.总结
MyBatis集成到Spring后，只有两件事稍微有不同：
- 1）Cofiguration的实例化是读取applicationContext.xml，而不是mybatis-config.xml
- 2）mapper对象是方法级别的，Spring通过FactoryBean进行增强巧妙地解决了这一问题
参考
- 1）享学课堂Lison老师笔记