MyBatis原理（2）-执行流程 1 BoundSql生成

MyBatis执行两种方式：
1.

	SqlSession openSession = sqlSessionFactory.openSession();
		Dept d = new Dept();
		d.setId(1506720);
		Object dept = openSession.selectOne("dao.DeptDAO1.select",d);
		System.out.println(dept);

2.

DeptMapper mapper = openSession.getMapper(DeptMapper.class);
		Dept dept2= mapper.select(d);
		System.out.println(dept2);

方式1：
1.DefaultSqlSessionFactory

  @Override
  public SqlSession openSession() {
    return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
  }

 public ExecutorType getDefaultExecutorType() {
    return defaultExecutorType;
  }
  protected ExecutorType defaultExecutorType = ExecutorType.SIMPLE;

public enum ExecutorType {
  SIMPLE, REUSE, BATCH
}

private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
     //XMLConfigBuilder#environmentsElement加载
      final Environment environment = configuration.getEnvironment();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
       //新建一个事务
      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();
    }
  }

Configuration#newExecutor 生成相应的Executor

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);
    }
   //缓存
    if (cacheEnabled) {
     //后面统一分析Executor集合和其子类，这里将SimpleExecutor包装为一个 
     //CachingExecutor
      executor = new CachingExecutor(executor);
    }
    //调用拦截器链中注册的拦截器（如果拦截类型是Executor），每个拦截器会对当前
   //Executor进行动态代理，如果有n个拦截器拦截Executor，会生成对Executor的n层代理， 
  //后面再进行详细分析
    executor = (Executor) interceptorChain.pluginAll(executor);
    return executor;
  }

SqlSession构造完毕后执行selectOne方法：

  @Override
  public  T selectOne(String statement, Object parameter) {
    // Popular vote was to return null on 0 results and throw exception on too many.
    List list = this.selectList(statement, parameter);
    if (list.size() == 1) {
      return list.get(0);
    } else if (list.size() > 1) {
      throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
    } else {
      return null;
    }
  }

  @Override
  public  List selectList(String statement, Object parameter) {
    return this.selectList(statement, parameter, RowBounds.DEFAULT);
  }

RowBounds //TODO
继续调用重载的selectList

  @Override
  public  List selectList(String statement, Object parameter, RowBounds rowBounds) {
    try {
      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();
    }
  }
//包装参数为StrictMap
private Object wrapCollection(final Object object) {
    if (object instanceof Collection) {
      StrictMap