mybatis源码解析-启动配置&使用spring启动配置(一)

mybatis
mybatis, spring, 源码分析

什么是mybatis

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录

mybatis用来做什么

针对数据库提供便携的高度灵活定制化sql，且使用简单

版本

基于mybatis-3.4.4版本

mybatis配置

mybatis-config.xml,copy自test下org.apache.ibatis.autoconstructor

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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>
    <!-- autoMappingBehavior should be set in each test case -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC">
                <property name="" value=""/>
            </transactionManager>
            <dataSource type="UNPOOLED">
                <property name="driver" value="org.hsqldb.jdbcDriver"/>
                <property name="url" value="jdbc:hsqldb:mem:automapping"/>
                <property name="username" value="sa"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/apache/ibatis/autoconstructor/AutoConstructorMapper.xml"/>
    </mappers>
</configuration>

构建SqlSessionFactory

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  private static SqlSessionFactory sqlSessionFactory;
@BeforeClass
public static void setUp() throws Exception {
  // create a SqlSessionFactory
  final Reader reader = Resources.getResourceAsReader("org/apache/ibatis/autoconstructor/mybatis-config.xml");
  sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);//构建
  reader.close();
  // populate in-memory database
  final SqlSession session = sqlSessionFactory.openSession();//获取session
  final Connection conn = session.getConnection();//打开连接
  dbReader.close();
  session.close();
}

源码分析

SqlSessionFactoryBuilder

使用构建器模式构建对象

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SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

SqlSessionFactoryBuilder

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public class SqlSessionFactoryBuilder {
  public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
  }
  public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }
   ...
  public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
  }
}

XMLConfigBuilder

基于xpath进行解析

  • propertiesElement
  • typeAliasesElement
  • pluginElement
  • objectFactoryElement
  • objectWrapperFactoryElement
  • reflectorFactoryElement
  • settingsElement
  • environmentsElement
  • databaseIdProviderElement
  • typeHandlerElement
  • mapperElement

image
具体相关配置请参考官方中文文档

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在解析mapper时，如果为resource节点会创建XMLMapperBuilder继续进行parse

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public class XMLConfigBuilder extends BaseBuilder {
  private boolean parsed;
  private XPathParser parser;
  private String environment;
  private ReflectorFactory localReflectorFactory = new DefaultReflectorFactory();
  
  public Configuration parse() {
    if (parsed) {
      throw new BuilderException("Each XMLConfigBuilder can only be used once.");
    }
    parsed = true;
    parseConfiguration(parser.evalNode("/configuration"));//基于xpath进行解析
    return configuration;
  }
  private void parseConfiguration(XNode root) {
    try {
      //issue #117 read properties first
      propertiesElement(root.evalNode("properties"));
      Properties settings = settingsAsProperties(root.evalNode("settings"));
      loadCustomVfs(settings);
      typeAliasesElement(root.evalNode("typeAliases"));
      pluginElement(root.evalNode("plugins"));
      objectFactoryElement(root.evalNode("objectFactory"));
      objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
      reflectorFactoryElement(root.evalNode("reflectorFactory"));
      settingsElement(settings);
      // read it after objectFactory and objectWrapperFactory issue #631
      environmentsElement(root.evalNode("environments"));
      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);
    }
  }
  ...
}

与spring整合

SqlSessionFactoryBean

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<!-- spring和MyBatis，不需要mybatis的配置映射文件 -->
	<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<!-- 自动扫描mapping.xml文件 -->
		<property name="mapperLocations" value="classpath:dal/**/*.xml"></property>
	</bean>

SqlSessionFactoryBean 实现了FactoryBean通过getObject->afterPropertiesSet->buildSqlSessionFactory 进行构建

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public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory>, InitializingBean, ApplicationListener<ApplicationEvent> {
  private static final Log logger = LogFactory.getLog(SqlSessionFactoryBean.class);
  private Resource configLocation;
  private Resource[] mapperLocations;
  private DataSource dataSource;
  private TransactionFactory transactionFactory;
  private Properties configurationProperties;
  private SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
  private SqlSessionFactory sqlSessionFactory;
  private String environment = SqlSessionFactoryBean.class.getSimpleName(); // EnvironmentAware requires spring 3.1
  private boolean failFast;
  private Interceptor[] plugins;
  private TypeHandler<?>[] typeHandlers;
  private String typeHandlersPackage;
  private Class<?>[] typeAliases;
  private String typeAliasesPackage;
  private Class<?> typeAliasesSuperType;
  private DatabaseIdProvider databaseIdProvider; // issue #19. No default provider.
  private ObjectFactory objectFactory;
  private ObjectWrapperFactory objectWrapperFactory;
 
  /**
   * {@inheritDoc}
   */
  public void afterPropertiesSet() throws Exception {
    notNull(dataSource, "Property 'dataSource' is required");
    notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");
    this.sqlSessionFactory = buildSqlSessionFactory();
  }
  /**
   * Build a {@code SqlSessionFactory} instance.
   *
   * The default implementation uses the standard MyBatis {@code XMLConfigBuilder} API to build a
   * {@code SqlSessionFactory} instance based on an Reader.
   *
   * @return SqlSessionFactory
   * @throws IOException if loading the config file failed
   */
  protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
    Configuration configuration;
    XMLConfigBuilder xmlConfigBuilder = null;
    if (this.configLocation != null) {
      xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
      configuration = xmlConfigBuilder.getConfiguration();
    } else {
      if (logger.isDebugEnabled()) {
        logger.debug("Property 'configLocation' not specified, using default MyBatis Configuration");
      }
      configuration = new Configuration();
      configuration.setVariables(this.configurationProperties);
    }
    if (this.objectFactory != null) {
      configuration.setObjectFactory(this.objectFactory);
    }
    if (this.objectWrapperFactory != null) {
      configuration.setObjectWrapperFactory(this.objectWrapperFactory);
    }
    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 (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();
    }
    Environment environment = new Environment(this.environment, this.transactionFactory, this.dataSource);
    configuration.setEnvironment(environment);
    if (this.databaseIdProvider != null) {
      try {
        configuration.setDatabaseId(this.databaseIdProvider.getDatabaseId(this.dataSource));
      } catch (SQLException e) {
        throw new NestedIOException("Failed getting a databaseId", e);
      }
    }
    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);
  }
  /**
   * {@inheritDoc}
   */
  public SqlSessionFactory getObject() throws Exception {
    if (this.sqlSessionFactory == null) {
      afterPropertiesSet();
    }
    return this.sqlSessionFactory;
  }
  /**
   * {@inheritDoc}
   */
  public Class<? extends SqlSessionFactory> getObjectType() {
    return this.sqlSessionFactory == null ? SqlSessionFactory.class : this.sqlSessionFactory.getClass();
  }
  /**
   * {@inheritDoc}
   */
  public boolean isSingleton() {
    return true;
  }
}

MapperScannerConfigurer

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<!-- DAO接口所在包名，Spring会自动查找其下的类 -->
	<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
		<property name="basePackage" value="com.kite.xxx.mapper" />
		<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
	</bean>

MapperScannerConfigurer:注册到spring容器中,实现BeanDefinitionRegistryPostProcessor接口spring会进行调用注册

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public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {
  private String basePackage;
  private boolean addToConfig = true;
  private SqlSessionFactory sqlSessionFactory;
  private SqlSessionTemplate sqlSessionTemplate;
  private String sqlSessionFactoryBeanName;
  private String sqlSessionTemplateBeanName;
  private Class<? extends Annotation> annotationClass;
  private Class<?> markerInterface;
  private ApplicationContext applicationContext;
  private String beanName;
  private boolean processPropertyPlaceHolders;
  private BeanNameGenerator nameGenerator;
  /**
   * {@inheritDoc}
   * 
   * @since 1.0.2
   */
  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);
    scanner.registerFilters();
    scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
  }
}

参考