Mybatis之是如何执行你的SQL的（SQL执行过程，参数解析过程，结果集封装过程）

Myabtis的SQL的执行是通过SqlSession。默认的实现类是DefalutSqlSession。通过源码可以发现，selectOne最终会调用selectList这个方法。

  @Override
  public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
    try {
　　　　　//获取MappedStatement  通过id 到configuration里面
      MappedStatement ms = configuration.getMappedStatement(statement);
      return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error querying database.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

通过上面可以发现是通过Executor去执行查询。但是executor是个接口，是什么时候指定的用什么执行器呢。

因为SqlSession是通过SqlSessionFactory接口获取的，实现类是DefaultSqlSessionFactory

  private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      final Executor executor = configuration.newExecutor(tx, execType);
      return new DefaultSqlSession(configuration, executor, autoCommit);
    } catch (Exception e) {
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }

public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
    executorType = executorType == null ? defaultExecutorType : executorType;
    executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
    Executor executor;
    if (ExecutorType.BATCH == executorType) {
      executor = new BatchExecutor(this, transaction);
    } else if (ExecutorType.REUSE == executorType) {
      executor = new ReuseExecutor(this, transaction);
    } else {
      executor = new SimpleExecutor(this, transaction);
    }
    if (cacheEnabled) {
      executor = new CachingExecutor(executor);
    }
    executor = (Executor) interceptorChain.pluginAll(executor);
    return executor;
  }

可以看到默认的是SimpleExecutor;然后默认的是开启缓存的，所以最终应该是一个CachingExecutor,但是CachingExecutor有一个构造器参数是前面的执行器。

这是一种典型的装饰器设计模式

下面那行代码你现在只需要知道如果有Executor的拦截器，就会返回一个代理对象，在执行executor方法前，会执行拦截器。这是动态代理。

后面讲Myabtis拦截器原理的时候会详细介绍。

这下知道了是CachingExecotor，来看下CachingExecutor方法；

 public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
    BoundSql boundSql = ms.getBoundSql(parameterObject);
    CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
    return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  }

① 先看是如何获取BoundSql  这个对象，包含了sql,params等信息。

  public BoundSql getBoundSql(Object parameterObject) {
    BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
    List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
    if (parameterMappings == null || parameterMappings.isEmpty()) {
      boundSql = new BoundSql(configuration, boundSql.getSql(), parameterMap.getParameterMappings(), parameterObject);
    }

    // check for nested result maps in parameter mappings (issue #30)
    for (ParameterMapping pm : boundSql.getParameterMappings()) {
      String rmId = pm.getResultMapId();
      if (rmId != null) {
        ResultMap rm = configuration.getResultMap(rmId);
        if (rm != null) {
          hasNestedResultMaps |= rm.hasNestedResultMaps();
        }
      }
    }

可以发现从sqlSource中获取BoundSql

一，DynamicSqlSourcre

public class DynamicSqlSource implements SqlSource {

  private Configuration configuration;
  private SqlNode rootSqlNode;

  public DynamicSqlSource(Configuration configuration, SqlNode rootSqlNode) {
    this.configuration = configuration;
    this.rootSqlNode = rootSqlNode;
  }

  @Override
  public BoundSql getBoundSql(Object parameterObject) {
       这一块的操作就是替换sql里面${}部分
    DynamicContext context = new DynamicContext(configuration, parameterObject);
14     rootSqlNode.apply(context);
    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);
    Class<?> parameterType = parameterObject == null ? Object.class : parameterObject.getClass();
    SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
    BoundSql boundSql = sqlSource.getBoundSql(parameterObject);
    for (Map.Entry<String, Object> entry : context.getBindings().entrySet()) {
      boundSql.setAdditionalParameter(entry.getKey(), entry.getValue());
    }
    return boundSql;
  }

}

来看下是如何替换sql的：

  public DynamicContext(Configuration configuration, Object parameterObject) {
    if (parameterObject != null && !(parameterObject instanceof Map)) {
         //如果参数类型不是map则构造一个MetaObject; //todo 这一块干嘛的目前还不清楚，后面研究mybatis反射时候研究
         //这个对象 保存着Configuration的那个几个factory 反射factory 驼峰Factory，创建对象factory
      MetaObject metaObject = configuration.newMetaObject(parameterObject);
      bindings = new ContextMap(metaObject);
    } else {
      bindings = new ContextMap(null);
    }
    bindings.put(PARAMETER_OBJECT_KEY, parameterObject);//_paramter
    bindings.put(DATABASE_ID_KEY, configuration.getDatabaseId());
  }

rootSqlNode.apply实际上接口的方法，这是根据节点的类别去执行，我们正常的MixedSqlNode实际上就是SqlNode数组类型，

这里只拿TextSqlNode做例子来看：

  @Override
  public boolean apply(DynamicContext context) {
    GenericTokenParser parser = createParser(new BindingTokenParser(context, injectionFilter));
    context.appendSql(parser.parse(text));
    return true;
  }

看过上一篇的应该对这段有了解， 就是用具体解析类来解析节点内容来,parser获取${}中间变量的名字，然后BindingTokenParser去处理；

parser.parses就是把sql里面每个${}替换成相应的值的作用

    public BindingTokenParser(DynamicContext context, Pattern injectionFilter) {
      this.context = context;
      this.injectionFilter = injectionFilter;
    }

    @Override
    public String handleToken(String content) {
         //从参数对象里面获取值返回
      Object parameter = context.getBindings().get("_parameter");
      if (parameter == null) {
        context.getBindings().put("value", null);
           //是不是基本类型
      } else if (SimpleTypeRegistry.isSimpleType(parameter.getClass())) {
        context.getBindings().put("value", parameter);
      }
         //获取到对应值,这一块很复杂，有时间在研究。
      Object value = OgnlCache.getValue(content, context.getBindings());
      String srtValue = (value == null ? "" : String.valueOf(value)); // issue #274 return "" instead of "null"
      checkInjection(srtValue);
      return srtValue;
    }

    private void checkInjection(String value) {
      if (injectionFilter != null && !injectionFilter.matcher(value).matches()) {
        throw new ScriptingException("Invalid input. Please conform to regex" + injectionFilter.pattern());
      }
    }
  }

好了 到此为止 sql里面${}都已经替换成该有的值了，根据变量名获取Value这一块下回研究下在另外写篇文章。

然后看这段代码：

SqlSource sqlSource = sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());
BoundSql boundSql = sqlSource.getBoundSql(parameterObject);

这一段也很重要 实际上是填充boundSql里面parameterMapping的

来看SqlSourceBuilder

  public SqlSource parse(String originalSql, Class<?> parameterType, Map<String, Object> additionalParameters) {
    ParameterMappingTokenHandler handler = new ParameterMappingTokenHandler(configuration, parameterType, additionalParameters);
    GenericTokenParser parser = new GenericTokenParser("#{", "}", handler);
    String sql = parser.parse(originalSql);
    return new StaticSqlSource(configuration, sql, handler.getParameterMappings());
  }

这一块代码应该很熟悉了吧， 实际上就是把#{}替换成？ 同时记录下参数的类型等信息，因为逻辑前面有介绍，直接看ParameterMappingTokenHandler的方法

    public String handleToken(String content) {
         //记录参数
      parameterMappings.add(buildParameterMapping(content));
         //替换成？
      return "?";
    }

    private ParameterMapping buildParameterMapping(String content) {
      Map<String, String> propertiesMap = parseParameterMapping(content);
      String property = propertiesMap.get("property");
      Class<?> propertyType;
      if (metaParameters.hasGetter(property)) { // issue #448 get type from additional params
        propertyType = metaParameters.getGetterType(property);
      } else if (typeHandlerRegistry.hasTypeHandler(parameterType)) {
        propertyType = parameterType;
      } else if (JdbcType.CURSOR.name().equals(propertiesMap.get("jdbcType"))) {
        propertyType = java.sql.ResultSet.class;
      } else if (property != null) {
        MetaClass metaClass = MetaClass.forClass(parameterType, configuration.getReflectorFactory());
        if (metaClass.hasGetter(property)) {
          propertyType = metaClass.getGetterType(property);
        } else {
          propertyType = Object.class;
        }
      } else {
        propertyType = Object.class;
      }
      ParameterMapping.Builder builder = new ParameterMapping.Builder(configuration, property, propertyType);
      Class<?> javaType = propertyType;
         设置每个参数类型等。
      String typeHandlerAlias = null;
      for (Map.Entry<String, String> entry : propertiesMap.entrySet()) {
        String name = entry.getKey();
        String value = entry.getValue();
        if ("javaType".equals(name)) {
          javaType = resolveClass(value);
          builder.javaType(javaType);
        } else if ("jdbcType".equals(name)) {
          builder.jdbcType(resolveJdbcType(value));
        } else if ("mode".equals(name)) {
          builder.mode(resolveParameterMode(value));
        } else if ("numericScale".equals(name)) {
          builder.numericScale(Integer.valueOf(value));
        } else if ("resultMap".equals(name)) {
          builder.resultMapId(value);
        } else if ("typeHandler".equals(name)) {
          typeHandlerAlias = value;
        } else if ("jdbcTypeName".equals(name)) {
          builder.jdbcTypeName(value);
        } else if ("property".equals(name)) {
          // Do Nothing
        } else if ("expression".equals(name)) {
          throw new BuilderException("Expression based parameters are not supported yet");
        } else {
          throw new BuilderException("An invalid property '" + name + "' was found in mapping #{" + content + "}.  Valid properties are " + parameterProperties);
        }
      }
      if (typeHandlerAlias != null) {
        builder.typeHandler(resolveTypeHandler(javaType, typeHandlerAlias));
      }
      return builder.build();
    }

现在回过头开始看CachingExecutor的query方法了

  public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
      throws SQLException {
       //这块就是mybatis的二级缓存
    Cache cache = ms.getCache();
    if (cache != null) {
      flushCacheIfRequired(ms);
      if (ms.isUseCache() && resultHandler == null) {
        ensureNoOutParams(ms, parameterObject, boundSql);
        @SuppressWarnings("unchecked")
        List<E> list = (List<E>) tcm.getObject(cache, key);
        if (list == null) {
          list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
          tcm.putObject(cache, key, list); // issue #578 and #116
        }
        return list;
      }
    }
       //最终调用的还是CachingExecutor里装饰的那个执行器
    return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  }

这个方法是所有执行器父类的BaseExecutor来实现的

  public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
    ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
    if (closed) {
      throw new ExecutorException("Executor was closed.");
    }
    if (queryStack == 0 && ms.isFlushCacheRequired()) {
      clearLocalCache();
    }
    List<E> list;
    try {
      queryStack++;
      list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
      if (list != null) {
        handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
      } else {
        list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
      }
    } finally {
      queryStack--;
    }
    if (queryStack == 0) {
      for (DeferredLoad deferredLoad : deferredLoads) {
        deferredLoad.load();
      }
      // issue #601
      deferredLoads.clear();
      if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
        // issue #482
        clearLocalCache();
      }
    }
    return list;
  }

//这里应该就是mybatis的一级缓存，直接看从数据库查询数据

  private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
    List<E> list;
    localCache.putObject(key, EXECUTION_PLACEHOLDER);
    try {
　　　　  //在子类中实现的 doQuery 查询出来结果放入一级缓存
      list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
    } finally {
      localCache.removeObject(key);
    }
    localCache.putObject(key, list);
    if (ms.getStatementType() == StatementType.CALLABLE) {
      localOutputParameterCache.putObject(key, parameter);
    }
    return list;
  }

看SimpleExecutor的doQuery的实现

  public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
    Statement stmt = null;
    try {
      Configuration configuration = ms.getConfiguration();
         //创建StatementHandler的代理对象，有的话返回代理对象，没有返回默认的RoutingStatmenthandler 典型的责任链模式
      StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
      stmt = prepareStatement(handler, ms.getStatementLog());
      return handler.<E>query(stmt, resultHandler);
    } finally {
      closeStatement(stmt);
    }
  }

接下来看下是怎么创建合适的Statement对象的，

  private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
    Statement stmt;
    Connection connection = getConnection(statementLog);
    stmt = handler.prepare(connection);
5     handler.parameterize(stmt);//设置参数
    return stmt;
  }

RoutingStatmenthandler

@Override
public Statement prepare(Connection connection) throws SQLException {
  return delegate.prepare(connection);
}

@Override
public void parameterize(Statement statement) throws SQLException {
  delegate.parameterize(statement);
}

调用的都是装饰的statementHander ,delegate是在RoutingStatementHandler构造器初始化的；

 public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {

    switch (ms.getStatementType()) {
      case STATEMENT:
        delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case PREPARED:
        delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case CALLABLE:
        delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      default:
        throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
    }

  }

可以看出来是根据ms保存的，三张就是Statement的三种，我们直接看预编译的，PreparedStatementHandler

实际上一些公共方法在BaseStatementHandler实现了

  public Statement prepare(Connection connection) throws SQLException {
    ErrorContext.instance().sql(boundSql.getSql());
    Statement statement = null;
    try {
      statement = instantiateStatement(connection);
      setStatementTimeout(statement);
      setFetchSize(statement);
      return statement;
    } catch (SQLException e) {
      closeStatement(statement);
      throw e;
    } catch (Exception e) {
      closeStatement(statement);
      throw new ExecutorException("Error preparing statement.  Cause: " + e, e);
    }
  }

instantiateStatement子类PreparedStatementHandler实现

  protected Statement instantiateStatement(Connection connection) throws SQLException {
    String sql = boundSql.getSql();
    if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
      String[] keyColumnNames = mappedStatement.getKeyColumns();
      if (keyColumnNames == null) {
        return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
      } else {
        return connection.prepareStatement(sql, keyColumnNames);
      }
    } else if (mappedStatement.getResultSetType() != null) {
      return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
    } else {
      return connection.prepareStatement(sql);
    }
  }

上面就是根据mappedStatement的resultType不同创建不同构造器的Statement；

下面来看下参数是怎么设置的。PreparedStatementHandler，但是handler是里面的paramterHandler是什么实现类呢？什么时候注入的呢？

  public void parameterize(Statement statement) throws SQLException {
    parameterHandler.setParameters((PreparedStatement) statement);
  }

来看下BaseStatementHandler的构造器

  protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
    this.configuration = mappedStatement.getConfiguration();
    this.executor = executor;
    this.mappedStatement = mappedStatement;
    this.rowBounds = rowBounds;

    this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
    this.objectFactory = configuration.getObjectFactory();

    if (boundSql == null) { // issue #435, get the key before calculating the statement
      generateKeys(parameterObject);
      boundSql = mappedStatement.getBoundSql(parameterObject);
    }

    this.boundSql = boundSql;
    //都说是相当于注册参数处理器，结果集处理器了。下面看默认的参数处理器是啥
    this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
18     this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
  }

  public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
      //可以看出来就是从mappenStatement的语言注册器创建参数处理器。实际上就一个语言处理器。
    ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
    parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
    return parameterHandler;
  }

默认的就是XMLLanguageDriver

public class XMLLanguageDriver implements LanguageDriver {

  @Override
  public ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
    return new DefaultParameterHandler(mappedStatement, parameterObject, boundSql);
  }

接下来就看DefaultParameterHandler怎么实现setParameters()

  @Override
  public void setParameters(PreparedStatement ps) {
    ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
    List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
    if (parameterMappings != null) {
      for (int i = 0; i < parameterMappings.size(); i++) {
        ParameterMapping parameterMapping = parameterMappings.get(i);
        if (parameterMapping.getMode() != ParameterMode.OUT) {
          Object value;
          String propertyName = parameterMapping.getProperty();
          if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
            value = boundSql.getAdditionalParameter(propertyName);
          } else if (parameterObject == null) {
            value = null;
          } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
            value = parameterObject;
          } else {
            MetaObject metaObject = configuration.newMetaObject(parameterObject);
            value = metaObject.getValue(propertyName);
          }
          TypeHandler typeHandler = parameterMapping.getTypeHandler();
          JdbcType jdbcType = parameterMapping.getJdbcType();
          if (value == null && jdbcType == null) {
                //这里有bug 如果传入值为0 也没设置参数jdbctype  会报错，这块可以给根据javaType给默认的类型
            jdbcType = configuration.getJdbcTypeForNull();
          }
          try {
            typeHandler.setParameter(ps, i + 1, value, jdbcType);
          } catch (TypeException e) {
            throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
          } catch (SQLException e) {
            throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
          }
        }
      }
    }
  }

这块就很简单了 根据每个参数JavaType jdbctype设设置。到此为止 prepareStatement的参数就都设置完了。

来看下 查询return handler.<E>query(stmt, resultHandler);

实际上也是PreparedStatementHandler实现的

  @Override
  public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
    PreparedStatement ps = (PreparedStatement) statement;
    ps.execute();
      //执行就不说了，就看下面 使用结果处理器来处理结果集 返回一个List
    return resultSetHandler.<E> handleResultSets(ps);
  }

resultSetHandler在父类构造器初始化的。看下默认的是什么吧

  public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, RowBounds rowBounds, ParameterHandler parameterHandler,
      ResultHandler resultHandler, BoundSql boundSql) {
3     ResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, mappedStatement, parameterHandler, resultHandler, boundSql, rowBounds);
    resultSetHandler = (ResultSetHandler) interceptorChain.pluginAll(resultSetHandler);
    return resultSetHandler;
  }

public List<Object> handleResultSets(Statement stmt) throws SQLException {
    ErrorContext.instance().activity("handling results").object(mappedStatement.getId());

    final List<Object> multipleResults = new ArrayList<Object>();

    int resultSetCount = 0;
       //ResultSet的包装类ResultSet，同时获取数据库的MetaData数据，包括数据表列名、列的类型、类序号等
    ResultSetWrapper rsw = getFirstResultSet(stmt);

    List<ResultMap> resultMaps = mappedStatement.getResultMaps();
    int resultMapCount = resultMaps.size();
    validateResultMapsCount(rsw, resultMapCount);
    while (rsw != null && resultMapCount > resultSetCount) {
      ResultMap resultMap = resultMaps.get(resultSetCount);
14       handleResultSet(rsw, resultMap, multipleResults, null);
      rsw = getNextResultSet(stmt);
      cleanUpAfterHandlingResultSet();
      resultSetCount++;
    }

    String[] resultSets = mappedStatement.getResulSets();
    if (resultSets != null) {
      while (rsw != null && resultSetCount < resultSets.length) {
        ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
        if (parentMapping != null) {
          String nestedResultMapId = parentMapping.getNestedResultMapId();
          ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
          handleResultSet(rsw, resultMap, null, parentMapping);
        }
        rsw = getNextResultSet(stmt);
        cleanUpAfterHandlingResultSet();
        resultSetCount++;
      }
    }

    return collapseSingleResultList(multipleResults);
  }

  private void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
    try {
      if (parentMapping != null) {
 4         handleRowValues(rsw, resultMap, null, RowBounds.DEFAULT, parentMapping);
      } else {
        if (resultHandler == null) {
          DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory);
 8           handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
          multipleResults.add(defaultResultHandler.getResultList());
        } else {
          handleRowValues(rsw, resultMap, resultHandler, rowBounds, null);
        }
      }
    } finally {
      // issue #228 (close resultsets)
      closeResultSet(rsw.getResultSet());
    }
  }

  private void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
    if (resultMap.hasNestedResultMaps()) {
      ensureNoRowBounds();
      checkResultHandler();
       //嵌套结果集
      handleRowValuesForNestedResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
    } else {
       //简单的结果集
      handleRowValuesForSimpleResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
    }
  }

  private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
      throws SQLException {
    DefaultResultContext<Object> resultContext = new DefaultResultContext<Object>();
    skipRows(rsw.getResultSet(), rowBounds);
    while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
      ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
      Object rowValue = getRowValue(rsw, discriminatedResultMap); //获取每一行的值
      storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
    }
  }

  private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap) throws SQLException {
    final ResultLoaderMap lazyLoader = new ResultLoaderMap();
       //创建数据对象的类对象  //todo这一块好复杂，有时间但单独在分析。
    Object resultObject = createResultObject(rsw, resultMap, lazyLoader, null);
    if (resultObject != null && !typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {
      final MetaObject metaObject = configuration.newMetaObject(resultObject);
      boolean foundValues = !resultMap.getConstructorResultMappings().isEmpty();
      if (shouldApplyAutomaticMappings(resultMap, false)) {
           //这一块就是为这个对象挨个赋值了
        foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, null) || foundValues;
      }
      foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, null) || foundValues;
      foundValues = lazyLoader.size() > 0 || foundValues;
      resultObject = foundValues ? resultObject : null;
      return resultObject;
    }
    return resultObject;
  }

  private boolean applyAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
    List<UnMappedColumAutoMapping> autoMapping = createAutomaticMappings(rsw, resultMap, metaObject, columnPrefix);
    boolean foundValues = false;
    if (autoMapping.size() > 0) {
         //遍历表的每一项 给对象赋值。
      for (UnMappedColumAutoMapping mapping : autoMapping) {
         //根据对应的java类型调用不同getResult获取值 如String, getString(); Int getInt()
        final Object value = mapping.typeHandler.getResult(rsw.getResultSet(), mapping.column);
        // issue #377, call setter on nulls
        if (value != null || configuration.isCallSettersOnNulls()) {
          if (value != null || !mapping.primitive) {
            metaObject.setValue(mapping.property, value);
          }
          foundValues = true;
        }
      }
    }
    return foundValues;
  }

到此为止，整个过程结束，结果集封装理解不是特别多，还有就是其中一些细节要以后慢慢推敲。如果有的地方解释的不对的地方希望看到的能及时提出探讨，万分感谢