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mybatis整合spring

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mybatis整合spring

当前spring是最热门的框架之一，很多框架都需要和spring整合，将组件交给spring的IOC容器来管理，下面来带大家来简单地配置一下mybatis和spring的整合

添加依赖

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<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.5.5</version>
</dependency>

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>5.1.48</version>
</dependency>

<!-- mybatis整合spring -->
<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis-spring</artifactId>
  <version>1.3.3</version>
</dependency>

<!-- spring 相关依赖 -->
<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-jdbc</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-core</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-aop</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-context</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-beans</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-aspects</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-tx</artifactId>
  <version>4.3.29.RELEASE</version>
</dependency>

mybatis配置文件

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <settings>
        <!-- 开启二级缓存 -->
        <setting name="cacheEnabled" value="true"/>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <!-- 延迟加载的全局开关。当开启时，所有关联对象都会延迟加载。 特定关联关系中可通过设置 fetchType 属性来覆盖该项的开关状态。 -->
        <setting name="lazyLoadingEnabled" value="true"/>
        <!-- 开启时，任一方法的调用都会加载该对象的所有延迟加载属性。 否则，每个延迟加载属性会按需加载 -->
        <setting name="aggressiveLazyLoading" value="false"/>
    </settings>

    <typeAliases>
        <!-- typeAlias为某个类起别名 -->
        <typeAlias type="com.zhanghe.study.mybatis.model.User" alias="User"/>
        
        <!-- 为某个包下所有类批量起别名
            默认值为类名首字母小写
         -->
        <package name="com.zhanghe.study.mybatis.model"/>
    </typeAliases>

    <!-- 数据库厂商标识 -->
    <databaseIdProvider type="DB_VENDOR">
        <!-- name为使用DatabaseMetaData#getDatabaseProductName()返回的厂商名称
             value为所设置的别名,使用databaseId时使用别名即可 -->
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
    </databaseIdProvider>

</configuration>

spring配置文件

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<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mybatis="http://mybatis.org/schema/mybatis-spring"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd   http://mybatis.org/schema/mybatis-spring http://mybatis.org/schema/mybatis-spring.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">
    <context:component-scan base-package="com.zhanghe.study.mybatis"/>
    <!-- 引入数据库配置文件 -->
    <context:property-placeholder location="jdbc.properties"/>

    <!-- 数据源 -->
    <bean id="datasource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

    <!-- 事务管理器 -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="datasource"/>
    </bean>



    <!-- 创建sqlSessionFactory，SqlSessionFactoryBean是一个FactoryBean，会调用getObject方法来获得SqlSessionFactory对象，其实现了InitializingBean，在afterPropertiesSet方法中构建了SqlSessionFactory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="datasource"/>
        <!-- mybatis全局配置文件的位置 也可以不使用mybatis全局配置 所有信息都可以在该bean中使用property来配置 -->
        <property name="configLocation" value="mybatis-config1.xml"/>
        <!-- mapper映射文件的位置 -->
        <property name="mapperLocations" value="classpath*:mapper/**/*.xml"/>
    </bean>
        <!-- 亲测两种方式都可以 -->
    <!-- 方式一：扫描所有的mapper接口,使得接口自动注入 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.zhanghe.study.mybatis.mapper"/>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
    </bean>
  <!-- 方式二：扫描所有的mapper接口,使得接口自动注入 -->
<!--
    <mybatis:scan base-package="com.zhanghe.study.mybatis.mapper"/>
-->
    <!-- 事务管理器 -->
    <tx:annotation-driven transaction-manager="transactionManager"/>
</beans>

单测结果

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/**
 * mybatis、spring整合测试
 * @author zh
 * @date 2021/1/15 16:08
 */
public class MybatisSpringTest {

    private ApplicationContext context;

    private SqlSessionFactory sqlSessionFactory;

    @Before
    public void beanFactory(){
        context = new ClassPathXmlApplicationContext("applicationContext.xml");
        sqlSessionFactory = context.getBean(SqlSessionFactory.class);
    }

    @Test
    public void testbeanAutoWired(){
        UserMapper userMapper = context.getBean(UserMapper.class);
        System.out.println(userMapper);
        UserService userService = context.getBean(UserService.class);
        userService.print();

    }

    @Test
    public void testTwoLevelCache(){
        SqlSession session = sqlSessionFactory.openSession();
        // mybatis为接口创建代理对象
        UserMapper userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.selectUser(8);
        System.out.println(user);
        userMapper.updateUser(user);
        session.close();
        SqlSession session1 = sqlSessionFactory.openSession();

        UserMapper userMapper1 = session1.getMapper(UserMapper.class);
        User user1 = userMapper1.selectUser(8);
        System.out.println(user1);
        System.out.println(user == user1);

        session1.close();
    }

}

参考地址http://mybatis.org/spring/zh/getting-started.html

分析

SqlSessionFactoryBean创建SqlSessionFactory

先来看一下SqlSessionFactoryBean是怎么创建SqlSessionFactory的，看这个命名像是一个FactoryBean，看一下实现，果然实现了FactoryBean和InitializingBean

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public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ApplicationEvent>

那么接下来就是看getObject()方法和afterPropertiesSet()方法了

getObject()

发现getObject()方法也是调用afterPropertiesSet()方法，那就只需要看afterPropertiesSet()方法了

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public SqlSessionFactory getObject() throws Exception {
  if (this.sqlSessionFactory == null) {
    afterPropertiesSet();
  }

  return this.sqlSessionFactory;
}
afterPropertiesSet()

忽略掉组织Configuration对象，其实最后就是调用了mybatis的sqlSessionFactoryBuilder.build(configuration)，OK，生成了SqlSessionFactory对象

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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();
}


protected SqlSessionFactory buildSqlSessionFactory() throws IOException {

    Configuration configuration;

    XMLConfigBuilder xmlConfigBuilder = null;
    if (this.configuration != null) {
      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) {
      xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
      configuration = xmlConfigBuilder.getConfiguration();
    } else {
      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);
      }
    }

    if (this.objectFactory != null) {
      configuration.setObjectFactory(this.objectFactory);
    }

    if (this.objectWrapperFactory != null) {
      configuration.setObjectWrapperFactory(this.objectWrapperFactory);
    }

    if (this.vfs != null) {
      configuration.setVfsImpl(this.vfs);
    }

    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");
        }
      }
    }

    if (!isEmpty(this.typeAliases)) {
      for (Class<?> typeAlias : this.typeAliases) {
        configuration.getTypeAliasRegistry().registerAlias(typeAlias);
        if (LOGGER.isDebugEnabled()) {
          LOGGER.debug("Registered type alias: '" + typeAlias + "'");
        }
      }
    }

    if (!isEmpty(this.plugins)) {
      for (Interceptor plugin : this.plugins) {
        configuration.addInterceptor(plugin);
        if (LOGGER.isDebugEnabled()) {
          LOGGER.debug("Registered plugin: '" + plugin + "'");
        }
      }
    }

    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");
        }
      }
    }

    if (!isEmpty(this.typeHandlers)) {
      for (TypeHandler<?> typeHandler : this.typeHandlers) {
        configuration.getTypeHandlerRegistry().register(typeHandler);
        if (LOGGER.isDebugEnabled()) {
          LOGGER.debug("Registered type handler: '" + typeHandler + "'");
        }
      }
    }

    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);
      }
    }

    if (this.cache != null) {
      configuration.addCache(this.cache);
    }

    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();
      }
    }

    if (this.transactionFactory == null) {
      this.transactionFactory = new SpringManagedTransactionFactory();
    }

    configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource));

    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");
      }
    }

    return this.sqlSessionFactoryBuilder.build(configuration);
  }

MapperScannerConfigurer扫描mapper

其实除了MapperScannerConfigurer之外，spring还提供了一个MapperFactoryBean，但是每一个Mapper都需要配置，太麻烦了，这里就直接分析MapperScannerConfigurer，先看一下结构，实现了BeanDefinitionRegistryPostProcessor、InitializingBean、ApplicationContextAware、BeanNameAware

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public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware

那接下来就是分析BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry和InitializingBean#afterPropertiesSet

afterPropertiesSet
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// 只是检测了一下basePackage属性不能为空
public void afterPropertiesSet() throws Exception {
  notNull(this.basePackage, "Property 'basePackage' is required");
}
postProcessBeanDefinitionRegistry
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public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
  // 处理${}属性占位来完成属性文件的加载
  if (this.processPropertyPlaceHolders) {
    processPropertyPlaceHolders();
  }

  // 创建scanner对象，进行属性设置
  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();
  // 进行扫描
  scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}

扫描

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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);
}
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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;
  }

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
   Assert.notEmpty(basePackages, "At least one base package must be specified");
   Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<BeanDefinitionHolder>();
   for (String basePackage : basePackages) {
      Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
      for (BeanDefinition candidate : candidates) {
         ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
         candidate.setScope(scopeMetadata.getScopeName());
         String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
         if (candidate instanceof AbstractBeanDefinition) {
            postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
         }
         if (candidate instanceof AnnotatedBeanDefinition) {
            AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
         }
         if (checkCandidate(beanName, candidate)) {
            BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
            definitionHolder =
                  AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
            beanDefinitions.add(definitionHolder);
            registerBeanDefinition(definitionHolder, this.registry);
         }
      }
   }
   return beanDefinitions;
}

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    GenericBeanDefinition definition;
  // 循环遍历构造MapperFactoryBean类型的bean
    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
      definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59
      // 构造MapperFactoryBean类型的bean
      definition.setBeanClass(this.mapperFactoryBean.getClass());

      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) {
        if (logger.isDebugEnabled()) {
          logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
        }
        definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
      }
    }
  }
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