一、MybatisSpring的使用
1.創建 Maven 工程，
2.添加依賴，代碼如下
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7-ybe</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>2.0.6-ybe</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.20</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.3.16</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>5.3.16</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.2.8</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.2.20.RELEASE</version>
</dependency>
3.添加物體如下，
package com.ybe.entity;
import java.io.Serializable;
public class Book implements Serializable {
int id;
double price;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
}
4.添加 Mapper介面以及BookMapper.xml檔案，
public interface BookMapper {
Book getBook(@Param("id") int id);
}
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.ybe.mapper.BookMapper">
<cache></cache>
<select id="getBook" resultType="com.ybe.entity.Book">
select * from book where id = #{id}
</select>
</mapper>
5.添加 BookService 和 BookServiceImpl代碼如下，
package com.ybe.service;
import com.ybe.entity.Book;
public interface BookSerivce {
Book getBook(int id);
}
package com.ybe.service.impl;
import com.ybe.entity.Book;
import com.ybe.mapper.BookMapper;
import com.ybe.service.BookSerivce;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class BookServiceImpl implements BookSerivce {
@Autowired
BookMapper bookMapper;
public Book getBook(int id) {
return bookMapper.getBook(id);
}
}
6.添加配置類，代碼如下
package com.ybe.config;
@Configuration
@MapperScan(basePackages = {"com.ybe.mapper"})
@ComponentScan(basePackages = {"com.ybe"})
public class MyBatisConfig {
@Bean
public SqlSessionFactoryBean sqlSessionFactory(DataSource dataSource) throws IOException {
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
factoryBean.setDataSource(dataSource);
factoryBean.setConfigLocation(new ClassPathResource("mybatis.xml"));
factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath:com/ybe/mapper/*.xml"));
factoryBean.setTypeAliases(Book.class);
return factoryBean;
}
@Bean
public DataSource dataSource(){
DruidDataSource dataSource = new DruidDataSource();
dataSource.setUsername("xxx");
dataSource.setPassword("xxx");
dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://localhost:3306/aopTest?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT%2B8");
return dataSource;
}
@Bean
public DataSourceTransactionManager transactionManager(DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}
}
7.添加主類代碼，代碼如下
AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(MyBatisConfig.class);
BookSerivce bookSerivce = configApplicationContext.getBean(BookSerivce.class);
Book book = bookSerivce.getBook(1);
System.out.println(book.getId());
二、Mybatis和Spring的整合
? 因為Mybatis中使用的是Mapper.class 介面來找到資料庫sql陳述句，并且是通過SqlSessionFactory的SqlSession來連接資料庫和執行Sql陳述句的，所以Mybatis和Spring的整合，其實就是把Mybatis的SqlSessionFactory類和Mapper.Class介面注入到SpringIOC中，并且SqlSessionFactory類中的事務管理物件（SpringManagedTransactionFactory ）會集成Spring的事務，
? 整個整合的程序分為兩部分，第一部分 Mapper介面注入；第二部分 SqlSessionFactoryBean 注入，
2.1 Mapper 介面注入
? 試想一下我們在寫Mapper介面的時候并沒有寫實作類，只是寫了Mapper.xml檔案，那在注入到Spring容器中，具體的實作類是啥？我這里直接給答案，Mapper介面在Spring容器中對應的實作類是一個MapperFactoryBean
原理
? 通過配置@MapperScan(basePackages = {"com.ybe.mapper"}) 注解，向 BeanDefinitionRegistry 中添加型別為 MapperScannerConfigurer 的BeanDefinition物件并且初始化物件相關屬性，在org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors 中會進行呼叫MapperScannerConfigurer 的postProcessBeanDefinitionRegistry 方法，該方法會掃描配置的包路徑下的Mapper介面class檔案，生成BeanClass為MapperFactoryBean的ScannedGenericBeanDefinition，注冊到 BeanDefinitionRegistry 中，
原始碼決議
- @MapperScan注解原始碼如下
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MapperScannerRegistrar.class)
@Repeatable(MapperScans.class)
- 在 org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors 方法中，會先執行 org.springframework.context.annotation.ConfigurationClassPostProcessor#processConfigBeanDefinitions的方法，其中會執行MapperScannerRegistrar類的registerBeanDefinitions方法，向 BeanDefinitionRegistry 注冊了一個型別為 MapperScannerConfigurer的BeanDefinition物件，代碼如下，
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
registry.registerBeanDefinition(beanName, builder.getBeanDefinition());
-
MapperScannerConfigurer實作了BeanDefinitionRegistryPostProcessor介面，MapperScannerConfigurer主要用來掃描具體的 Mapper介面class檔案，生成BeanClass型別為MapperFactoryBean的ScannedGenericBeanDefinition物件后注入 BeanDefinitionRegistry 中，具體類圖如下
-
在org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors中會接著執行，MapperScannerConfigurer的postProcessBeanDefinitionRegistry 方法，postProcessBeanDefinitionRegistry中大概邏輯為
搜索指定包下面的Mapper介面，
// 開始搜索 basePackage
scanner.scan(
StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
生成ScannedGenericBeanDefinition，并以Mapper介面名稱為BeanName注入到BeanDefinitionRegistry物件中，
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
然后再設定ScannedGenericBeanDefinition的BeanClass型別為MapperFactoryBean類， 關鍵代碼代碼如下
// 設定 definition 的 建構式的引數值型別為 beanClassName，
// 在創建 MapperFactoryBean 時，會根據beanClassName創建類，然后把類作為引數呼叫MapperFactoryBean帶引數的構造方法
definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59
// 設定 definition 的 Bean 型別為 MapperFactoryBean.class
definition.setBeanClass(this.mapperFactoryBeanClass);
-
每個Mapper介面檔案對應的BeanDefinition為 ScannedGenericBeanDefinition，BeanDefinition的BeanClass實作類為 MapperFactoryBean 類，此時查看beanFactory的 beanDefinitionMap 中的值，如下圖
-
MapperFactoryBean是一個泛型類，泛型用來表示不同介面型別，繼承了SqlSessionDaoSupport類，該類中存盤了Maybatis的SqlSession工廠類，MapperFactoryBean也是一個實作了FactoryBean
的類，用來回傳具體的型別以及根據型別來生成具體的Mapper介面代理類，
@Override
public T getObject() throws Exception {
// 回傳根據介面型別回傳 SqlSession中的Mapper代理物件
return getSqlSession().getMapper(this.mapperInterface);
}
/**
* {@inheritDoc}
*/
@Override
public Class<T> getObjectType() {
return this.mapperInterface;
}
-
在beanFactory.preInstantiateSingletons()方法中會把BeanDefinition生成具體的Bean物件，在創建 MapperFactoryBean 物件的時候會呼叫帶引數的構造方法(上面有具體說明)，因為在配置類中我們注入了SqlSessionFactoryBean物件(具體決議程序在下面章節講解)，SqlSessionFactoryBean物件實作了FactoryBean
介面，在Srping容器中會回傳SqlSessionFactory型別物件，在給MapperFactoryBean屬性賦值的時候會把SqlSessionFactoryBean的實際SqlSessionFactory物件賦值給sqlSessionTemplate屬性，最侄訓在beanFactory.singletonObjects物件中添加以Mapper介面名稱為key，以 MapperFactoryBean 型別為value的 記錄， -
在獲取Mapper介面的Bean物件的時候，會呼叫getObject()方法，其中會調SqlSessionTemplate的getMapper()，代碼如下
@Override
public <T> T getMapper(Class<T> type) {
return getConfiguration().getMapper(type, this);
}
- 以上呼叫Configuration的getMapper()方法，configuration就是Mybatis的類了，代碼如下，
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
// 根據Mapper介面型別獲取已經注冊的物件
return mapperRegistry.getMapper(type, sqlSession);
}
- 回傳創建的動態代理物件，這里回傳的動態代理物件之后不會更新beanFactory.singletonObjects的物件，并且會進行快取處理，關鍵代碼如下
@SuppressWarnings("unchecked")
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
// 根據 Mapper 介面型別獲取已經注冊的物件
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
// 創建動態代理物件
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
- 總結一下，beanFactory.singletonObjects關于Mapper介面存盤的Bean物件是泛型的MapperFactoryBean物件，但是根據Mapper介面獲取Bean物件會回傳上面的動態代理物件，并且動態代理物件會快取在beanFactory.factoryBeanObjectCache中，這是因為MapperFactoryBean實作的FactoryBean
介面，
2.1 SqlSessionFactoryBean 注入
SqlSessionFactoryBean介紹
通過@Bean方式可以將SqlSessionFactoryBean物件注入到Spring容器，SqlSessionFactoryBean物件在MapperFactoryBean物件中會用到，注入代碼如下，
@Bean
public SqlSessionFactoryBean sqlSessionFactory(DataSource dataSource) throws IOException {
// 創建 SqlSessionFactoryBean 的類
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
// 設定資料源
factoryBean.setDataSource(dataSource);
// 設定組態檔路徑
factoryBean.setConfigLocation(new ClassPathResource("mybatis.xml"));
// 設定 mybaits.xml 檔案
factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
.getResources("classpath:com/ybe/mapper/*.xml"));
// 設定別名
factoryBean.setTypeAliases(Book.class);
return factoryBean;
}
SqlSessionFactoryBean的類繼承關系圖如下，
SqlSessionFactoryBean實作了InitializingBean介面 ，會在初始化后會執行afterPropertiesSet方法，其中會呼叫buildSqlSessionFactory()方法進行SqlSessionFactory的創建，SqlSessionFactoryBean也實作了FactoryBean
@Override
public SqlSessionFactory getObject() throws Exception {
if (this.sqlSessionFactory == null) {
afterPropertiesSet();
}
return this.sqlSessionFactory;
}
buildSqlSessionFactory()具體邏輯
? 1. 根據 configLocation 創建 XMLConfigBuilder 以及 Configuration物件
xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
targetConfiguration = xmlConfigBuilder.getConfiguration();
? 2. 讀取SqlSessionFactoryBean的屬性物件給 targetConfiguration 賦值
Optional.ofNullable(this.objectFactory).ifPresent(targetConfiguration::setObjectFactory);
Optional.ofNullable(this.objectWrapperFactory).ifPresent(targetConfiguration::setObjectWrapperFactory);
Optional.ofNullable(this.vfs).ifPresent(targetConfiguration::setVfsImpl);
if (hasLength(this.typeAliasesPackage)) {
scanClasses(this.typeAliasesPackage, this.typeAliasesSuperType).stream()
.filter(clazz -> !clazz.isAnonymousClass()).filter(clazz -> !clazz.isInterface())
.filter(clazz -> !clazz.isMemberClass()).forEach(targetConfiguration.getTypeAliasRegistry()::registerAlias);
}
......
? 3. 決議主組態檔
xmlConfigBuilder.parse();
? 4. targetConfiguration設定環境變數，如果配置的transactionFactory 事務工廠類為 null，則創建 SpringManagedTransactionFactory 事務工廠類，該事務工廠會直接呼叫org.springframework.jdbc.datasource.DataSourceUtils去獲取資料庫連接物件，所以和Spring的事務進行了集成，代碼如下，
// 設定環境變數，如果事務工程類為 null，則創建 SpringManagedTransactionFactory 事務工廠類
targetConfiguration.setEnvironment(new Environment(this.environment,
this.transactionFactory == null ? new SpringManagedTransactionFactory() : this.transactionFactory,
this.dataSource));
? 5. 如果 mapperLocations 不為null ，則回圈遍歷 xxxMapper.xml 檔案流，決議之后給 targetConfiguration 的相關物件賦值，代碼如下，
for (Resource mapperLocation : this.mapperLocations) {
if (mapperLocation == null) {
continue;
}
try {
// 構建 XMLMapperBuilder 物件，進行mapper.xml 檔案資源決議
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),
targetConfiguration, mapperLocation.toString(), targetConfiguration.getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception e) {
throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);
} finally {
ErrorContext.instance().reset();
}
LOGGER.debug(() -> "Parsed mapper file: '" + mapperLocation + "'");
}
- 總結一下，整個程序比較簡單，其主要就是Mybaits初始化的程序，更詳細Mybatis初始化程序請參考上一篇文章，
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標籤：Java