MybatisPlusAutoConfiguration
Introduce mybatis-plus-boot-starter, there is spring.factories under the package, the content is as follows:
# Auto Configure org.springframework.boot.env.EnvironmentPostProcessor=\ com.baomidou.mybatisplus.autoconfigure.SafetyEncryptProcessor org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.baomidou.mybatisplus.autoconfigure.IdentifierGeneratorAutoConfiguration,\ com.baomidou.mybatisplus.autoconfigure.MybatisPlusLanguageDriverAutoConfiguration,\ com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConfiguration
MybatisPlusAutoConfigurationThis class injects components such as SqlSessionFactory and SqlSessionTemplate.
SqlSessionFactory
MybatisPlusAutoConfiguration#sqlSessionFactory, create SqlSessionFactory.
@Bean
@ConditionalOnMissingBean
public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {<!-- -->
MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
factory.setDataSource(dataSource);
//...
return factory. getObject();
}
MybatisSqlSessionFactoryBean#getObject
@Override
public SqlSessionFactory getObject() throws Exception {<!-- -->
if (this.sqlSessionFactory == null) {<!-- -->
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
MybatisSqlSessionFactoryBean#afterPropertiesSet
public void afterPropertiesSet() throws Exception {<!-- -->
notNull(dataSource, "Property 'dataSource' is required");
state((configuration == null & amp; & amp; configLocation == null) || !(configuration != null & amp; & amp; configLocation != null),
"Property 'configuration' and 'configLocation' can not be specified with together");
//TODO clean up resources, it is recommended not to keep this thing
SqlRunner. DEFAULT. close();
this.sqlSessionFactory = buildSqlSessionFactory();
}
MybatisSqlSessionFactoryBean#buildSqlSessionFactory, use MybatisXMLConfigBuilder to parse xml and build Configuration information.
@MapperScan
Add @MapperScan(basePackages = {"com.charles.mapper"}) to the startup class, and all classes that inherit BaseMapper under the directory will be scanned.
@Retention(RetentionPolicy.RUNTIME)
@Target({<!-- -->ElementType. TYPE})
@Documented
@Import({<!-- -->MapperScannerRegistrar.class})
@Repeatable(MapperScans. class)
public @interface MapperScan {<!-- -->
}
MapperScannerRegistrar
MapperScannerRegistrar implements ImportBeanDefinitionRegistrar, and injects MapperScannerConfigurer into the Spring container in the rewriting method MapperScannerRegistrar#registerBeanDefinitions()
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {<!-- -->
AnnotationAttributes mapperScanAttrs = AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
if (mapperScanAttrs != null) {<!-- -->
this.registerBeanDefinitions(importingClassMetadata, mapperScanAttrs, registry, generateBaseBeanName(importingClassMetadata, 0));
}
}
void registerBeanDefinitions(AnnotationMetadata annoMeta, AnnotationAttributes annoAttrs, BeanDefinitionRegistry registry, String beanName) {<!-- -->
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
builder.addPropertyValue("processPropertyPlaceHolders", true);
//...
builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(basePackages));
builder.setRole(2);
registry.registerBeanDefinition(beanName, builder.getBeanDefinition());
}
MapperScannerConfigurer
MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, rewrite method. Using ClassPathMapperScanner
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {<!-- -->
if (this. processPropertyPlaceHolders) {<!-- -->
this. 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(this. lazyInitialization)) {<!-- -->
scanner.setLazyInitialization(Boolean.valueOf(this.lazyInitialization));
}
if (StringUtils. hasText(this. defaultScope)) {<!-- -->
scanner.setDefaultScope(this.defaultScope);
}
scanner. registerFilters();
scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ",; \t\\
"));
}
ClassPathMapperScanner#doScan, scan under the specified package, and the type of registered Bean is MapperFactoryBean.
public Set<BeanDefinitionHolder> doScan(String... basePackages) {<!-- -->
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
if (beanDefinitions. isEmpty()) {<!-- -->
LOGGER. warn(() -> {<!-- -->
return "No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration.";
});
} else {<!-- -->
this.processBeanDefinitions(beanDefinitions);
}
return beanDefinitions;
}
private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {<!-- -->
BeanDefinitionRegistry registry = this. getRegistry();
Iterator var4 = beanDefinitions. iterator();
while(var4.hasNext()) {<!-- -->
BeanDefinitionHolder holder = (BeanDefinitionHolder)var4.next();
AbstractBeanDefinition definition = (AbstractBeanDefinition)holder.getBeanDefinition();
//...
try {<!-- -->
definition.getPropertyValues().add("mapperInterface", Resources.classForName(beanClassName));
} catch (ClassNotFoundException var10) {<!-- -->
}
definition.setBeanClass(this.mapperFactoryBeanClass);
//...
definition.setLazyInit(this.lazyInitialization);
if (!scopedProxy) {<!-- -->
if ("singleton".equals(definition.getScope()) & amp; & amp; this.defaultScope != null) {<!-- -->
definition.setScope(this.defaultScope);
}
if (!definition.isSingleton()) {<!-- -->
BeanDefinitionHolder proxyHolder = ScopedProxyUtils.createScopedProxy(holder, registry, true);
if (registry. containsBeanDefinition(proxyHolder. getBeanName())) {<!-- -->
registry. removeBeanDefinition(proxyHolder. getBeanName());
}
registry.registerBeanDefinition(proxyHolder.getBeanName(), proxyHolder.getBeanDefinition());
}
}
}
}
ClassPathMapperScanner#isCandidateComponent, specify the candidate class. needs to be an interface
protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {<!-- -->
return beanDefinition.getMetadata().isInterface() & amp; & amp; beanDefinition.getMetadata().isIndependent();
}
MapperFactoryBean
MapperFactoryBean#getObject, the object of this class in the Spring container.
public T getObject() throws Exception {<!-- -->
return this.getSqlSession().getMapper(this.mapperInterface);
}
MybatisMapperRegistry#getMapper (mybatis: MapperRegistry#getMapper)
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {<!-- -->
MybatisMapperProxyFactory<T> mapperProxyFactory = (MybatisMapperProxyFactory)this.knownMappers.get(type);
if (mapperProxyFactory == null) {<!-- -->
mapperProxyFactory = (MybatisMapperProxyFactory)this.knownMappers.entrySet().stream().filter((t) -> {<!-- -->
return ((Class)t. getKey()). getName(). equals(type. getName());
}).findFirst().map(Entry::getValue).orElseThrow(() -> {<!-- -->
return new BindingException("Type " + type + " is not known to the MybatisPlusMapperRegistry.");
});
}
try {<!-- -->
return mapperProxyFactory. newInstance(sqlSession);
} catch (Exception var5) {<!-- -->
throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
}
}
MybatisMapperProxyFactory#newInstance(), create a proxy class.
protected T newInstance(MybatisMapperProxy<T> mapperProxy) {<!-- -->
return Proxy.newProxyInstance(this.mapperInterface.getClassLoader(), new Class[]{<!-- -->this.mapperInterface}, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {<!-- -->
MybatisMapperProxy<T> mapperProxy = new MybatisMapperProxy(sqlSession, this.mapperInterface, this.methodCache);
return this.newInstance(mapperProxy);
}
Execute Mapper
MybatisMapperProxy.PlainMethodInvoker#invoke will be executed with the encapsulated MybatisMapperMethod
public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {<!-- -->
return this.mapperMethod.execute(sqlSession, args);
}
MybatisMapperMethod#execute, the core processing class
public Object execute(SqlSession sqlSession, Object[] args) {<!-- -->
Object result;
Object param;
switch(this.command.getType()) {<!-- -->
case INSERT:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.insert(this.command.getName(), param));
break;
case UPDATE:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.update(this.command.getName(), param));
break;
case DELETE:
param = this.method.convertArgsToSqlCommandParam(args);
result = this.rowCountResult(sqlSession.delete(this.command.getName(), param));
break;
case SELECT:
if (this.method.returnsVoid() & amp; & amp; this.method.hasResultHandler()) {<!-- -->
this. executeWithResultHandler(sqlSession, args);
result = null;
} else if (this. method. returnsMany()) {<!-- -->
result = this. executeForMany(sqlSession, args);
} else if (this. method. returnsMap()) {<!-- -->
result = this. executeForMap(sqlSession, args);
} else if (this. method. returnsCursor()) {<!-- -->
result = this. executeForCursor(sqlSession, args);
} else if (IPage. class. isAssignableFrom(this. method. getReturnType())) {<!-- -->
result = this. executeForIPage(sqlSession, args);
} else {<!-- -->
param = this.method.convertArgsToSqlCommandParam(args);
result = sqlSession. selectOne(this. command. getName(), param);
if (this.method.returnsOptional() & amp; & amp; (result == null || !this.method.getReturnType().equals(result.getClass()))) {<!-- -->
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession. flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + this.command.getName());
}
if (result == null & amp; & amp; this.method.getReturnType().isPrimitive() & amp; & amp; !this.method.returnsVoid()) {<!-- -->
throw new BindingException("Mapper method '" + this.command.getName() + " attempted to return null from a method with a primitive return type (" + this.method.getReturnType() + ") .");
} else {<!-- -->
return result;
}
}
Mybatis cache
DefaultSqlSession#selectList(), this method is used to query the collection
private <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {<!-- -->
try {<!-- -->
MappedStatement ms = configuration. getMappedStatement(statement);
return executor. query(ms, wrapCollection(parameter), rowBounds, handler);
} catch (Exception e) {<!-- -->
throw ExceptionFactory. wrapException("Error querying database. Cause: " + e, e);
} finally {<!-- -->
ErrorContext.instance().reset();
}
}
BaseExecutor#query(), the specific query method. A cache key will be generated based on information such as parameters to determine whether it exists in the cache. This cache is the first level cache.
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {<!-- -->
BoundSql boundSql = ms.getBoundSql(parameter);
CacheKey key = createCacheKey(ms, parameter, rowBounds, boundSql);
return query(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
@SuppressWarnings("unchecked")
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {<!-- -->
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if (closed) {<!-- -->
throw new ExecutorException("Executor was closed.");
}
if (queryStack == 0 & amp; & amp; ms.isFlushCacheRequired()) {<!-- -->
clearLocalCache();
}
List<E> list;
try {<!-- -->
queryStack++;
list = resultHandler == null ? (List<E>) localCache. getObject(key) : null;
if (list != null) {<!-- -->
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {<!-- -->
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {<!-- -->
queryStack--;
}
if (queryStack == 0) {<!-- -->
for (DeferredLoad deferredLoad : deferredLoads) {<!-- -->
deferredLoad.load();
}
// issue #601
deferredLoads. clear();
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {<!-- -->
// issue #482
clearLocalCache();
}
}
return list;
}
CachingExecutor#query() uses the second-level cache.
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
throws SQLException {<!-- -->
Cache cache = ms. getCache();
if (cache != null) {<!-- -->
flushCacheIfRequired(ms);
if (ms.isUseCache() & amp; & amp; resultHandler == null) {<!-- -->
ensureNoOutParams(ms, boundSql);
@SuppressWarnings("unchecked")
List<E> list = (List<E>) tcm. getObject(cache, key);
if (list == null) {<!-- -->
list = delegate. query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issues #578 and #116
}
return list;
}
}
return delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
SimpleExecutor#doQuery, the default BaseExecutor implementation of Mybatis is SimpleExecutor, and finally calls the SimpleExecutor#doQuery method.
@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {<!-- -->
Statement stmt = null;
try {<!-- -->
Configuration configuration = ms. getConfiguration();
StatementHandler handler = configuration. newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
stmt = prepareStatement(handler, ms.getStatementLog());
return handler. query(stmt, resultHandler);
} finally {<!-- -->
closeStatement(stmt);
}
}
