配置
欲在Spring中使用Mybatis，需要引入
org.mybatis
mybatis-spring
在Spring配置文件中添加Spring配置
classpath:mapper/*Mapper.xml
dataSource：数据源
configLocation：mybatis的配置文件路径
mapperLocations：mybatis的mapper的文件路径。
初始化过程
Spring-mybatis的初始化入口为
//org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet()
public void afterPropertiesSet() throws Exception {
notNull(dataSource, "Property 'dataSource' is required");
notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
this.sqlSessionFactory = buildSqlSessionFactory();
}
buildSqlSessionFactory函数可简化为
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
Configuration configuration;
XMLConfigBuilder xmlConfigBuilder = null;
xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
configuration = xmlConfigBuilder.getConfiguration();
//部分代码略
xmlConfigBuilder.parse();
//部分代码略
if (!isEmpty(this.mapperLocations)) {
for (Resource mapperLocation : this.mapperLocations) {
if (mapperLocation == null) {
continue;
}
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),
configuration, mapperLocation.toString(), configuration.getSqlFragments());
xmlMapperBuilder.parse();
}
}
//部分代码略
return this.sqlSessionFactoryBuilder.build(configuration);
}
XMLConfigBuilder解析mybaitis的配置文件
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
private void parseConfiguration(XNode root) {
try {
propertiesElement(root.evalNode("properties")); //issue #117 read properties first
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
settingsElement(root.evalNode("settings"));
environmentsElement(root.evalNode("environments")); // read it after objectFactory and objectWrapperFactory issue #631
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
XMLMapperBuilder对Mybatis的mapper文件进行解析
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingChacheRefs();
parsePendingStatements();
}
public XNode getSqlFragment(String refid) {
return sqlFragments.get(refid);
}
private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e);
}
}
至此，mybatis的配置文件，mapper文件解析完毕
最后通过sqlSessionFactoryBuilder.build函数返回一个SqlSessionFactory对象
public SqlSessionFactory build(Configuration config) {
return new DefaultSqlSessionFactory(config);
}
扫描Mapper接口
org.mybatis.spring.mapper.MapperScannerConfigurer
实现了Spring的BeanDefinitionRegistryPostProcessor接口，目的是为了向Spring注入mapper的代理类。
//org.mybatis.spring.mapper.MapperScannerConfigurer.postProcessBeanDefinitionRegistry
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
if (this.processPropertyPlaceHolders) {
processPropertyPlaceHolders();
}
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);
//注册类过滤器，
scanner.registerFilters();
scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
postProcessBeanDefinitionRegistry函数初始化ClassPathMapperScanner并扫描mapper接口所在的包。
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);
}
scan调用doScan函数
public Set doScan(String... basePackages) {
//获取包下的所有bean的beanDefinitionHolder，并将它们注入到Spring中。
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 {
for (BeanDefinitionHolder holder : beanDefinitions) {
GenericBeanDefinition definition = (GenericBeanDefinition) holder.getBeanDefinition();
//略
//修改Bean的class
definition.setBeanClass(MapperFactoryBean.class);
//代码略，如果显示的设置了sqlSessionFactory或者sqlSessionTemplate，就使用显示设置的信息，
//否则将根据类型自动获取Spring中的sqlSessionFactory或者sqlSessionTemplate
//（definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE)）。
//注：即使Scan未配置sqlSessionFactory，Spring也会自己自动获取容器中的sqlSessionFactory
}
}
return beanDefinitions;
}
MapperFactoryBean是一个factoryBean.将会在Bean初始化的时候返回Mybatis的mapper的代理类。
MapperFactoryBean
public class MapperFactoryBean extends SqlSessionDaoSupport implements FactoryBean {
//部分代码略
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
public Class getObjectType() {
return this.mapperInterface;
}
public boolean isSingleton() {
return true;
}
}
MapperFactoryBean实现FactoryBean接口，Spring在使用MapperFactoryBean创建对象时会调用getObject()函数。
因为SqlSessionFactory为DefaultSqlSessionFactory，DefaultSqlSessionFactory.openSession()返回SqlSession为DefaultSqlSession，所以上面的getSqlSession().getMapper(this.mapperInterface)最终会调用到DefaultSqlSession.getMapper(this.mapperInterface)函数。
//org.apache.ibatis.session.defaults.DefaultSqlSession
public T getMapper(Class type) {
return configuration.getMapper(type, this);
}
configuration.getMapper会调用到MapperRegistry.getMapper函数
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);
}
}
此后将使用动态代理生成mapperinterface的代理对象返回。