自動配置無非涉及幾個方面
- mapper 的代理註冊
- sql 語句的註冊
查看自動配置類#
路徑 ：D:\maven-repository\com\baomidou\mybatis-plus-boot-starter\3.4.1\mybatis-plus-boot-starter-3.4.1.jar!\META-INF\spring.factories
代碼解釋#
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties(MybatisPlusProperties.class)
@AutoConfigureAfter({DataSourceAutoConfiguration.class, MybatisPlusLanguageDriverAutoConfiguration.class})
public class MybatisPlusAutoConfiguration implements InitializingBean {
// 省略其他字段...
// 檢查配置文件是否存在
private void checkConfigFileExists() {
// 當需要檢查配置文件位置且位置不為空時執行
if (this.properties.isCheckConfigLocation() && StringUtils.hasText(this.properties.getConfigLocation())) {
Resource resource = this.resourceLoader.getResource(this.properties.getConfigLocation());
// 確保資源存在
Assert.state(resource.exists(),
"Cannot find config location: " + resource + " (please add config file or check your Mybatis configuration)");
}
}
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
// 創建 MybatisSqlSessionFactoryBean 實例，設置數據源
MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
factory.setDataSource(dataSource);
// 省略配置和設置其他屬性...
// 返回 SqlSessionFactory 實例
return factory.getObject();
}
// 檢查 Spring 容器中的 bean，並進行消費
private <T> void getBeanThen(Class<T> clazz, Consumer<T> consumer) {
if (this.applicationContext.getBeanNamesForType(clazz, false, false).length > 0) {
consumer.accept(this.applicationContext.getBean(clazz));
}
}
// 應用 Mybatis 配置
private void applyConfiguration(MybatisSqlSessionFactoryBean factory) {
MybatisConfiguration configuration = this.properties.getConfiguration();
// 省略其他配置...
factory.setConfiguration(configuration);
}
@Bean
@ConditionalOnMissingBean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
// 根據屬性返回 SqlSessionTemplate 實例
ExecutorType executorType = this.properties.getExecutorType();
return executorType != null ? new SqlSessionTemplate(sqlSessionFactory, executorType) : new SqlSessionTemplate(sqlSessionFactory);
}
// 省略其他內部類和方法...
}
這個類做了幾件事
- 註冊 SqlSessionFactory
這個類主要是為 SqlSessionTemplate 提供會話獲取工廠 當然了 mybatisplus 進一步封裝為 SqlSessionTemplate 為了和 spring 的事務結合 - 註冊 SqlSessionTemplate
- 註冊 AutoConfiguredMapperScannerRegistrar
我們看看 mapper 是怎麼註冊到 spring 容器裡面的#
public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar {
private BeanFactory beanFactory;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
if (!AutoConfigurationPackages.has(this.beanFactory)) {
logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.");
return; }
logger.debug("Searching for mappers annotated with @Mapper");
List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
if (logger.isDebugEnabled()) {
packages.forEach(pkg -> logger.debug("Using auto-configuration base package '{}'", pkg));
}
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
builder.addPropertyValue("processPropertyPlaceHolders", true);
builder.addPropertyValue("annotationClass", Mapper.class);
builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(packages));
BeanWrapper beanWrapper = new BeanWrapperImpl(MapperScannerConfigurer.class);
Stream.of(beanWrapper.getPropertyDescriptors())
// Need to mybatis-spring 2.0.2+
.filter(x -> x.getName().equals("lazyInitialization")).findAny()
.ifPresent(x -> builder.addPropertyValue("lazyInitialization", "${mybatis.lazy-initialization:false}"));
registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());
}
@Override
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
}
可以看到這個類註冊了一個 BeanDefinition 叫 MapperScannerConfigurer，再進去看看
public class MapperScannerConfigurer
implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
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);
scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
if (StringUtils.hasText(lazyInitialization)) {
scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
}
scanner.registerFilters();
scanner.scan(
StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
可以看到 裡面進一步使用 ClassPathMapperScanner 來掃描所有的 this.annotationClass 類
而上面配置 MapperScannerConfigurer 的時候是掃描這個註解
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
builder.addPropertyValue("processPropertyPlaceHolders", true);
builder.addPropertyValue("annotationClass", Mapper.class); //這裡
builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(packages));
其中 ClassPathMapperScanner 重寫了 doScan 方法
@Override
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
if (beanDefinitions.isEmpty()) {
LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
+ "' package. Please check your configuration.");
} else {
processBeanDefinitions(beanDefinitions);
}
return beanDefinitions;
}
點進去 processBeanDefinitions (beanDefinitions) 看看
private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
GenericBeanDefinition definition;
for (BeanDefinitionHolder holder : beanDefinitions) {
definition = (GenericBeanDefinition) holder.getBeanDefinition();
String beanClassName = definition.getBeanClassName();
LOGGER.debug(() -> "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName
+ "' mapperInterface");
// the mapper interface is the original class of the bean
// but, the actual class of the bean is MapperFactoryBean definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59
definition.setBeanClass(this.mapperFactoryBeanClass);
definition.getPropertyValues().add("addToConfig", this.addToConfig);
boolean explicitFactoryUsed = false;
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;
}
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;
}
if (!explicitFactoryUsed) {
LOGGER.debug(() -> "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}
definition.setLazyInit(lazyInitialization);
}
}
可以看到將掃描的 mapper 包裝為
definition.setBeanClass(this.mapperFactoryBeanClass);
這個類最後會註冊一個 mapper 代理
@Override
protected void checkDaoConfig() {
super.checkDaoConfig();
notNull(this.mapperInterface, "Property 'mapperInterface' is required");
Configuration configuration = getSqlSession().getConfiguration();
if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) {
try {
configuration.addMapper(this.mapperInterface);
} catch (Exception e) {
logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", e);
throw new IllegalArgumentException(e);
} finally {
ErrorContext.instance().reset();
}
}
}
/**
* {@inheritDoc}
*/@Override
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
我們進一步進去 configuration.addMapper (this.mapperInterface); 看看怎麼註冊的
public <T> void addMapper(Class<T> type) {
if (type.isInterface()) {
if (hasMapper(type)) {
// TODO 如果之前注入 直接返回
return;
// TODO 這裡就不拋異常了
// throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
}
boolean loadCompleted = false;
try {
knownMappers.put(type, new MybatisMapperProxyFactory<>(type));
MybatisMapperAnnotationBuilder parser = new MybatisMapperAnnotationBuilder(config, type);
parser.parse();
loadCompleted = true;
} finally {
if (!loadCompleted) {
knownMappers.remove(type);
}
}
}
}
這裡進一步的將 new MapperProxyFactory<>(type) 註冊到 knownMappers 中，我們點進去看看
public class MybatisMapperProxyFactory<T> {
@Getter
private final Class<T> mapperInterface;
@Getter
private final Map<Method, MybatisMapperProxy.MapperMethodInvoker> methodCache = new ConcurrentHashMap<>();
public MybatisMapperProxyFactory(Class<T> mapperInterface) {
this.mapperInterface = mapperInterface;
}
@SuppressWarnings("unchecked")
protected T newInstance(MybatisMapperProxy<T> mapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[]{mapperInterface}, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {
final MybatisMapperProxy<T> mapperProxy = new MybatisMapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
}
可以看到 最後是封裝為一個 MybatisMapperProxy 對象
public class MybatisMapperProxyFactory<T> {
@Getter
private final Class<T> mapperInterface;
@Getter
private final Map<Method, MybatisMapperProxy.MapperMethodInvoker> methodCache = new ConcurrentHashMap<>();
public MybatisMapperProxyFactory(Class<T> mapperInterface) {
this.mapperInterface = mapperInterface;
}
@SuppressWarnings("unchecked")
protected T newInstance(MybatisMapperProxy<T> mapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[]{mapperInterface}, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {
final MybatisMapperProxy<T> mapperProxy = new MybatisMapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
}
好了 mapper 怎麼註冊到 spring 的流程通了
sql 語句什麼時候註冊進去的呢？#
我們注意到 註冊 mapper 的時候下面還有兩行語句
MybatisMapperAnnotationBuilder parser = new MybatisMapperAnnotationBuilder(config, type);
parser.parse();
這裡就是註冊 sql 語句的地方，我們點進去看看
public void parse() {
String resource = type.toString();
if (!configuration.isResourceLoaded(resource)) {
loadXmlResource();
configuration.addLoadedResource(resource);
String mapperName = type.getName();
assistant.setCurrentNamespace(mapperName);
parseCache();
parseCacheRef();
InterceptorIgnoreHelper.InterceptorIgnoreCache cache = InterceptorIgnoreHelper.initSqlParserInfoCache(type);
for (Method method : type.getMethods()) {
if (!canHaveStatement(method)) {
continue;
}
if (getAnnotationWrapper(method, false, Select.class, SelectProvider.class).isPresent()
&& method.getAnnotation(ResultMap.class) == null) {
parseResultMap(method);
}
try {
parseStatement(method);
InterceptorIgnoreHelper.initSqlParserInfoCache(cache, mapperName, method);
SqlParserHelper.initSqlParserInfoCache(mapperName, method);
} catch (IncompleteElementException e) {
}
}
// TODO 注入 CURD 動態 SQL , 放在在最後, because 可能會有人會用註解重寫sql
try {
// https://github.com/baomidou/mybatis-plus/issues/3038
if (GlobalConfigUtils.isSupperMapperChildren(configuration, type)) {
parserInjector();
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new InjectorResolver(this));
}
}
parsePendingMethods();
}
其中有一句loadXmlResource();
我們點進去看看
private void loadXmlResource() {
// Spring may not know the real resource name so we check a flag
// to prevent loading again a resource twice // this flag is set at XMLMapperBuilder#bindMapperForNamespace if (!configuration.isResourceLoaded("namespace:" + type.getName())) {
String xmlResource = type.getName().replace('.', '/') + ".xml";
// #1347
InputStream inputStream = type.getResourceAsStream("/" + xmlResource);
if (inputStream == null) {
// Search XML mapper that is not in the module but in the classpath.
try {
inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
} catch (IOException e2) {
// ignore, resource is not required
}
}
if (inputStream != null) {
XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName());
xmlParser.parse();
}
}
}
可以看到這裡就是加載 xml 的地方String xmlResource = type.getName().replace('.', '/') + ".xml"; 這一句就是為什麼 xml 要和 mapper 放在一個文件夾的關鍵了，直接是吧後綴替換為 xml 再去讀取
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
這裡就是加載一些配置和一些 sql 語句了，接著就是註冊 mybatisplus 自帶的增刪改查了
// TODO 注入 CURD 動態 SQL , 放在在最後, because 可能會有人會用註解重寫sql
try {
// https://github.com/baomidou/mybatis-plus/issues/3038
if (GlobalConfigUtils.isSupperMapperChildren(configuration, type)) {
parserInjector();
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new InjectorResolver(this));
}
此文由 Mix Space 同步更新至 xLog
原始鏈接為 https://me.liuyaowen.cn/posts/codenotes/2024112