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就是让你懂 Spring 中 Mybatis 的花样配置

ImportNew 33 阅读
原文出处: 今天你不奋斗明天你就落后

一、前言

Mybatis作为一个优秀的存储过程和高级映射的持久层框架,目前在项目实践中运用的比较广泛,最近做项目时候发现了一种之前没见过的配置方式,这里总结下常用的配置方式以便备忘查找。

二、Spring中Mybatis的配置方案一

2.1 多数据源配置案例

(1)数据源配置
 <bean id="dataSourceForA" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
        <property name="url" value="${db1_url}" />
        <property name="username" value="$db1_user}" />
        <property name="password" value="${db1_passwd}" />
        <property name="maxWait" value="${db1_maxWait}" />
        <property name="maxActive" value="28" /> 
        <property name="initialSize" value="2" />
        <property name="minIdle" value="0" />
        <property name="timeBetweenEvictionRunsMillis" value="300000" />
        <property name="testOnBorrow" value="false" />
        <property name="testWhileIdle" value="true" />
        <property name="validationQuery" value="select 1 from dual" />
        <property name="filters" value="stat" />
    </bean>

(2)创建sqlSessionFactory
<bean id="sqlSessionFactoryForA" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="mapperLocations" value="classpath*:com/**/mapper1/*Mapper*.xml" /> 
        <property name="dataSource" ref="dataSourceForA" />
        <property name="typeAliasesPackage" value="com.zlx.***.dal" />
</bean>
    
(3)配置扫描器,扫描指定路径的mapper生成数据库操作代理类
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="annotationClass" value="javax.annotation.Resource"></property>
        <property name="basePackage" value="com.zlx1.***.dal.***.mapper" />
        <property name="sqlSessionFactory" ref="sqlSessionFactoryForA" />
</bean>

(4)数据源配置
 <bean id="dataSourceForB" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
        <property name="url" value="${db_url}" />
        <property name="username" value="$db_user}" />
        <property name="password" value="${db_passwd}" />
        <property name="maxWait" value="${db_maxWait}" />
        <property name="maxActive" value="28" /> 
        <property name="initialSize" value="2" />
        <property name="minIdle" value="0" />
        <property name="timeBetweenEvictionRunsMillis" value="300000" />
        <property name="testOnBorrow" value="false" />
        <property name="testWhileIdle" value="true" />
        <property name="validationQuery" value="select 1 from dual" />
        <property name="filters" value="stat" />
    </bean>

(5)创建sqlSessionFactory
<bean id="sqlSessionFactoryForB" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="mapperLocations" value="classpath*:com/**/mapper/*Mapper*.xml" /> 
        <property name="dataSource" ref="dataSourceForB" />
        <property name="typeAliasesPackage" value="com.zlx.***.dal" />
</bean>
    
(6)配置扫描器,扫描指定路径的mapper生成数据库操作代理类
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="annotationClass" value="javax.annotation.Resource"></property>
        <property name="basePackage" value="com.zlx.***.dal.***.mapper" />
        <property name="sqlSessionFactory" ref="sqlSessionFactoryForB" />
</bean>

2.1 原理简单介绍

2.1.1 SqlSessionFactory原理

(2)(5)作用是根据配置创建一个SqlSessionFactory,看下SqlSessionFactoryBean的代码知道它实现了FactoryBean和InitializingBean类,由于实现了InitializingBean,所以自然它的afterPropertiesSet方法,由于实现了FactoryBean类,所以自然会有getObject方法。下面看下时序图:

从时序图可知,SqlSessionFactoryBean类主要是通过属性配置创建SqlSessionFactory实例,具体是解析配置中所有的mapper文件放到configuration,然后作为构造函数参数实例化一个DefaultSqlSessionFactory作为SqlSessionFactory。

2.1.2 MapperScannerConfigurer原理

扫描指定路径的mapper生成数据库操作代理类
MapperScannerConfigurer 实现了 BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware接口,所以会重写一下方法:

//在bean注册到ioc后创建实例前修改bean定义和新增bean注册,这个是在context的refresh方法调用
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

//在bean注册到ioc后创建实例前修改bean定义或者属性值
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

//set属性设置后调用
void afterPropertiesSet() throws Exception;

//获取IOC容器上下文,在context的prepareBeanFactory中调用
void setApplicationContext(ApplicationContext applicationContext) throws BeansException;

//获取bean在ioc容器中名字,在context的prepareBeanFactory中调用
void setBeanName(String name);

先上个扫描mapper生成代理类并注册到ioc时序图:

首先MapperScannerConfigurer实现的afterPropertiesSet方法用来确保属性basePackage不为空

public void afterPropertiesSet() throws Exception {
    notNull(this.basePackage, "Property 'basePackage' is required");
  }

postProcessBeanFactory里面啥都没做,setBeanName获取了bean的名字,setApplicationContext里面获取了ioc上下文。下面看重要的方法postProcessBeanDefinitionRegistry,由于mybais是运行时候才通过解析mapper文件生成代理类注入到ioc,所以postProcessBeanDefinitionRegistry正好可以干这个事情。

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    if (this.processPropertyPlaceHolders) {
      processPropertyPlaceHolders();
    }

    //构造一个ClassPathMapperScanner查找mapper
    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
    scanner.setAddToConfig(this.addToConfig);
    //javax.annotation.Resource
    scanner.setAnnotationClass(this.annotationClass);
    scanner.setMarkerInterface(this.markerInterface);
    //引用sqlSessionFactory
    scanner.setSqlSessionFactory(this.sqlSessionFactory);
    scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
    scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
    scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
    //ioc上下文
    scanner.setResourceLoader(this.applicationContext);
    scanner.setBeanNameGenerator(this.nameGenerator);
    scanner.registerFilters();
   //basePackage=com.alibaba.***.dal.***.mapper,com.alibaba.rock.auth.mapper,com.alibaba.rock.workflow.dal.workflow.mapper
    scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
  }

下面重点看下scan方法:

public Set<BeanDefinitionHolder> doScan(String... basePackages) {
    //根据指定路径去查找对应mapper的接口类,并转化为beandefination
    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 {
      //修改接口类bean的beandefination
      processBeanDefinitions(beanDefinitions);
    }

    return beanDefinitions;
  }

其中super.doScan(basePackages);根据指定路径查找mapper接口类,并生成bean的定义对象,对象中包含beanclassname,beanclass属性,最后注册该bean到ioc容器。下面看下最重要的processBeanDefinitions方法对bean定义的改造。

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    GenericBeanDefinition definition;
    for (BeanDefinitionHolder holder : beanDefinitions) {
      definition = (GenericBeanDefinition) holder.getBeanDefinition();

      // 上面讲的扫描后beanclass设置的为mapper接口类,但是这里修改为MapperFactoryBean,MapperFactoryBean代理了mapper接口类,并且实际mapper接口类作为构造函数传入了      definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); 
      definition.setBeanClass(this.mapperFactoryBean.getClass());
      definition.getPropertyValues().add("addToConfig", this.addToConfig);

      //设置属性配置中的sqlSessionFactory
      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);
      }
    }
  }

注:这里修改了mapper接口类的beandefination中的beanclass为MapperFactoryBean,它则负责生产数据类操作代理类,实际mapper接口类作为构造函数传入了 。由于只修改了beanclass,没有修改beanname,所以我们从容器中获取时候无感知的。

在上一个代理bean如何构造的时序图:

下面看下MapperFactoryBean是如何生成代理类的:
首先,上面代码设置了MapperFactoryBean的setSqlSessionFactory方法:

public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
    if (!this.externalSqlSession) {
      this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);
    }
  }

上面方法创建了sqlSession,由于MapperFactoryBean为工厂bean所以实例化时候会调用getObject方法:

 public T getObject() throws Exception {
    return getSqlSession().getMapper(this.mapperInterface);
  }

其实是调用了SqlSessionTemplate->getMapper,其中mapperInterface就是创建MapperFactoryBean时候的构造函数参数。

public <T> T getMapper(Class<T> type) {
    return getConfiguration().getMapper(type, this);
  }

这里调用getConfiguration().getMapper(type, this);实际是DefaultSqlSessionFactory里面的configration的getMapper方法:

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
   //knownMappers是上面时序图中步骤6设置进入的。
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
      throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
      return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
      throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
  }
 protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
  }

  public T newInstance(SqlSession sqlSession) {
   //代理回调类为MapperProxy
    final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
  }

在上一个实际执行sql时候调用代理类的序列图:

所以当调用实际的数据库操作时候会调用MapperProxy的invoke方法:

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    if (Object.class.equals(method.getDeclaringClass())) {
      try {
        return method.invoke(this, args);
      } catch (Throwable t) {
        throw ExceptionUtil.unwrapThrowable(t);
      }
    }
    final MapperMethod mapperMethod = cachedMapperMethod(method);
    return mapperMethod.execute(sqlSession, args);
  }

mapperMethod.execute(sqlSession, args);里面实际是调用当前mapper对应的SqlSessionTemplate的数据库操作,而它有委托给了代理类sqlSessionProxy,sqlSessionProxy是在SqlSessionTemplate的构造函数里面创建的:

public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType,
      PersistenceExceptionTranslator exceptionTranslator) {

    notNull(sqlSessionFactory, "Property 'sqlSessionFactory' is required");
    notNull(executorType, "Property 'executorType' is required");

    this.sqlSessionFactory = sqlSessionFactory;
    this.executorType = executorType;
    this.exceptionTranslator = exceptionTranslator;
    this.sqlSessionProxy = (SqlSession) newProxyInstance(
        SqlSessionFactory.class.getClassLoader(),
        new Class[] { SqlSession.class },
        new SqlSessionInterceptor());
  }

所以最终数据库操作有被代理SqlSessionInterceptor执行:

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
      //有TransactionSynchronizationManager管理
      SqlSession sqlSession = getSqlSession(
          SqlSessionTemplate.this.sqlSessionFactory,
          SqlSessionTemplate.this.executorType,
          SqlSessionTemplate.this.exceptionTranslator);
      try {
        Object result = method.invoke(sqlSession, args);
        if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {
          // force commit even on non-dirty sessions because some databases require
          // a commit/rollback before calling close()
          sqlSession.commit(true);
        }
        return result;
      } catch (Throwable t) {
          .....
      }
    }

public static SqlSession getSqlSession(SqlSessionFactory sessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator) {

    notNull(sessionFactory, NO_SQL_SESSION_FACTORY_SPECIFIED);
    notNull(executorType, NO_EXECUTOR_TYPE_SPECIFIED);

    SqlSessionHolder holder = (SqlSessionHolder) TransactionSynchronizationManager.getResource(sessionFactory);

    SqlSession session = sessionHolder(executorType, holder);
    if (session != null) {
      return session;
    }

    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug("Creating a new SqlSession");
    }
   //这里看到了使用sessionfactory熟悉的打开了一个session
    session = sessionFactory.openSession(executorType);

    registerSessionHolder(sessionFactory, executorType, exceptionTranslator, session);

    return session;
  }

关于事务配置可移步:http://www.jianshu.com/p/1d882343c036

三、Spring中Mybatis的配置方案二

2.1 多数据源配置案例

(1)数据源配置
 <bean id="dataSourceForA" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
        <property name="url" value="${db1_url}" />
        <property name="username" value="$db1_user}" />
        <property name="password" value="${db1_passwd}" />
        <property name="maxWait" value="${db1_maxWait}" />
        <property name="maxActive" value="28" /> 
        <property name="initialSize" value="2" />
        <property name="minIdle" value="0" />
        <property name="timeBetweenEvictionRunsMillis" value="300000" />
        <property name="testOnBorrow" value="false" />
        <property name="testWhileIdle" value="true" />
        <property name="validationQuery" value="select 1 from dual" />
        <property name="filters" value="stat" />
    </bean>

(2)创建sqlSessionFactory
<bean id="sqlSessionFactoryForA" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="mapperLocations" value="classpath*:com/**/mapper1/*Mapper*.xml" /> 
        <property name="dataSource" ref="dataSourceForA" />
        <property name="typeAliasesPackage" value="com.zlx.***.dal" />
</bean>
    
(3)配置扫描器,扫描指定路径的mapper生成数据库操作代理类
  <mybatis:scan base-package="com.zlx1.***.dal" factory-ref="sqlSessionFactoryForA" annotation="javax.annotation.Resource"/>

(4)数据源配置
 <bean id="dataSourceForB" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />
        <property name="url" value="${db_url}" />
        <property name="username" value="$db_user}" />
        <property name="password" value="${db_passwd}" />
        <property name="maxWait" value="${db_maxWait}" />
        <property name="maxActive" value="28" /> 
        <property name="initialSize" value="2" />
        <property name="minIdle" value="0" />
        <property name="timeBetweenEvictionRunsMillis" value="300000" />
        <property name="testOnBorrow" value="false" />
        <property name="testWhileIdle" value="true" />
        <property name="validationQuery" value="select 1 from dual" />
        <property name="filters" value="stat" />
    </bean>

(5)创建sqlSessionFactory
<bean id="sqlSessionFactoryForB" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="mapperLocations" value="classpath*:com/**/mapper/*Mapper*.xml" /> 
        <property name="dataSource" ref="dataSourceForB" />
        <property name="typeAliasesPackage" value="com.zlx.***.dal" />
</bean>
    
(6)配置扫描器,扫描指定路径的mapper生成数据库操作代理类
    <mybatis:scan base-package="com.zlx.***.dal" factory-ref="sqlSessionFactoryForB" annotation="javax.annotation.Resource"/>

与上节不同在在于(3)(6)

3.2 原理简单介绍

这里只看 <mybatis:scan/> 标签解析,按照惯例看jar包的spring.handler找标签解析

MapperScannerBeanDefinitionParser的代码如下:

可知MapperScannerBeanDefinitionParser所做的事情和MapperScannerConfigurer类似都是内部搞了个ClassPathMapperScanner。

四、SpringBoot中Mybatis的配置方案

4.1 SpringBoot中多数据源使用

数据源一配置:

//三、设置扫描器
@MapperScan(basePackages = "com.alibaba.zlx.web.speech.mapper",sqlSessionFactoryRef="sqlSessionFactory1")
public class TddlAutoConfiguration {

    @Autowired
    private TddlProperties properties;

    //一、创建数据源
    @Primary
    @Bean(name = "dataSource1")
    public DataSource dataSource1() throws TddlException {
        TDataSource dataSource = new TDataSource();
        dataSource.setAppName(properties.getAppName());
        dataSource.setSharding(properties.getSharding());
        dataSource.setDynamicRule(properties.getDynamicRule());
        dataSource.init();

        return dataSource;
    }
    
    //二、创建SqlSessionFactory
    @Bean(name = "sqlSessionFactory1")
    @Primary
    public SqlSessionFactory sqlSessionFactoryBean1() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();

        sqlSessionFactoryBean.setDataSource(dataSource1());
        sqlSessionFactoryBean.setMapperLocations(resolveMapperLocations(new String[]{"classpath:mapper/*.xml"}));

        return sqlSessionFactoryBean.getObject();
    }
    
     //四、 创建事务管理器
    @Bean(name = "txManager1")
    @Primary
    public PlatformTransactionManager txManager1(@Qualifier("dataSource1")DataSource dataSource) {
        
        
        System.out.println("-----------dataource-----" + dataSource.toString());
        return new DataSourceTransactionManager(dataSource);
    }
    
    @Bean("sqlSessionTemplate1")
    @Primary
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactory1")SqlSessionFactory sqlSessionFactory) {
        System.out.println("-----------sqlSessionFactory-----" + sqlSessionFactory.toString());

        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

数据源二配置:

//三、设置扫描器
@MapperScan(basePackages = "com.alibaba.gh.web.speech.mapper", sqlSessionFactoryRef = "sqlSessionFactory2")

public class TddlAutoConfiguration2 {

    @Autowired
    private TddlProperties properties;

    //一、创建数据源
    @Bean(name = "dataSource2")
    public DataSource dataSource2() throws TddlException {
        TDataSource dataSource = new TDataSource();
        dataSource.setAppName(properties.getAppName());
        dataSource.setSharding(properties.getSharding());
        dataSource.setDynamicRule(properties.getDynamicRule());
        dataSource.init();

        return dataSource;
    }

    //二、创建SqlSessionFactory
    @Bean(name = "sqlSessionFactory2")
    public SqlSessionFactory sqlSessionFactoryBean1() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();

        sqlSessionFactoryBean.setDataSource(dataSource2());
        sqlSessionFactoryBean.setMapperLocations(resolveMapperLocations(new String[] { "classpath:mapper2/*.xml" }));

        return sqlSessionFactoryBean.getObject();
    }

    // 四、创建事务管理器
    @Bean(name = "txManager2")
    public PlatformTransactionManager txManager1(@Qualifier("dataSource2") DataSource dataSource) {

        System.out.println("-----------dataource-----" + dataSource.toString());
        return new DataSourceTransactionManager(dataSource);
    }
    @Bean("sqlSessionTemplate2")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactory2")SqlSessionFactory sqlSessionFactory) {
        System.out.println("-----------sqlSessionFactory-----" + sqlSessionFactory.toString());

        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

另外SqlSessionTemplate是对SqlSessionFactory的一个包装,这里每个数据源也配置了一个,如果想使用它的话,只需要修改@mapperscan,设置sqlSessionTemplateRef替换sqlSessionFactoryRef。

作者:ImportNew
原文地址:就是让你懂 Spring 中 Mybatis 的花样配置, 感谢原作者分享。

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