MyBatis深入理解和使用-MyBatis事务管理

事务管理

JDBC事务

public static boolean insert(Test test) throws SQLException {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/testdb?useUnicode=true&characterEncoding=utf-8&useSSL=false&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC", "test", "123456");
            // 自动提交设置为false
            connection.setAutoCommit(false);
            preparedStatement = connection.prepareStatement("INSERT INTO test VALUES (?,?,?)");
            if (null != test.getId()) {
                preparedStatement.setInt(1, test.getId());
            } else {
                preparedStatement.setNull(1, INTEGER);
            }
            preparedStatement.setInt(2, test.getNums());
            preparedStatement.setString(3, test.getName());
            preparedStatement.execute();
            connection.commit();
            return true;
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != connection) {
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return true;
    }

MyBatis自带事务

SqlSession --> Exxecutor --> Transaction --> Connection

之后就是JDBC的处理逻辑

Mybatis-Spring-x.x.x.jar

mapper是怎么注入进来的

XML 或者 java Config- ->MapperScannerConfigurer --> BeanDefinitionRegistryPostProcessor -->BeanFactoryPostProcessor告诉Spring去加载MyBatisConfig

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    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));
  }

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
    void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}

Annotation --> MapperScannerRegistrar -->ImportBeanDefinitionRegistrar 告诉Spring去加载MyBatisConfig

public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

    AnnotationAttributes annoAttrs = AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);

    // this check is needed in Spring 3.1
    if (resourceLoader != null) {
      scanner.setResourceLoader(resourceLoader);
    }

    Class<? extends Annotation> annotationClass = annoAttrs.getClass("annotationClass");
    if (!Annotation.class.equals(annotationClass)) {
      scanner.setAnnotationClass(annotationClass);
    }

    Class<?> markerInterface = annoAttrs.getClass("markerInterface");
    if (!Class.class.equals(markerInterface)) {
      scanner.setMarkerInterface(markerInterface);
    }

    Class<? extends BeanNameGenerator> generatorClass = annoAttrs.getClass("nameGenerator");
    if (!BeanNameGenerator.class.equals(generatorClass)) {
      scanner.setBeanNameGenerator(BeanUtils.instantiateClass(generatorClass));
    }

    Class<? extends MapperFactoryBean> mapperFactoryBeanClass = annoAttrs.getClass("factoryBean");
    if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) {
      scanner.setMapperFactoryBean(BeanUtils.instantiateClass(mapperFactoryBeanClass));
    }

    scanner.setSqlSessionTemplateBeanName(annoAttrs.getString("sqlSessionTemplateRef"));
    scanner.setSqlSessionFactoryBeanName(annoAttrs.getString("sqlSessionFactoryRef"));

    List<String> basePackages = new ArrayList<String>();
    for (String pkg : annoAttrs.getStringArray("value")) {
      if (StringUtils.hasText(pkg)) {
        basePackages.add(pkg);
      }
    }
    for (String pkg : annoAttrs.getStringArray("basePackages")) {
      if (StringUtils.hasText(pkg)) {
        basePackages.add(pkg);
      }
    }
    for (Class<?> clazz : annoAttrs.getClassArray("basePackageClasses")) {
      basePackages.add(ClassUtils.getPackageName(clazz));
    }
    scanner.registerFilters();
    scanner.doScan(StringUtils.toStringArray(basePackages));
  }

public interface ImportBeanDefinitionRegistrar {
    void registerBeanDefinitions(AnnotationMetadata var1, BeanDefinitionRegistry var2);
}

sqlsession的生命周期在没有@Transaction的情况下是request/method级别的；在有@Transaction的情况下

是@Transaction范围内的。

Mapper在没有spring的时候是Method级别的，在有的时候是全局的Singleton。

// set
definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); 
definition.setBeanClass(this.mapperFactoryBean.getClass());

// get
Configuration configuration = getSqlSession().getConfiguration();

分页查询

逻辑分页

org.apache.ibatis.executor.resultset.DefaultResultSetHandler # handleRowValuesForSimpleResultMap

private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
      throws SQLException {
    DefaultResultContext<Object> resultContext = new DefaultResultContext<Object>();
    // 判断要跳到响应的offset对应的位置
    skipRows(rsw.getResultSet(), rowBounds);
    while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
      ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
      Object rowValue = getRowValue(rsw, discriminatedResultMap);
      storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
    }
  }

// 具体判断逻辑
private void skipRows(ResultSet rs, RowBounds rowBounds) throws SQLException {
    if (rs.getType() != ResultSet.TYPE_FORWARD_ONLY) {
      if (rowBounds.getOffset() != RowBounds.NO_ROW_OFFSET) {
        rs.absolute(rowBounds.getOffset());
      }
    } else {
        //具体实现
      for (int i = 0; i < rowBounds.getOffset(); i++) {
        rs.next();
      }
    }
  }