- Mybatis初始化过程
	- 通过InputStream来获取配置文件
	- ClassLoaderWarpper中的getResourceAsStream可以根据配置的resoutce来获取到配置文件的输入六
	- 使用ClassLoader是因为类加载器可具有读取外部资源的能力
	- ![image.png](../assets/image_1714227673997_0.png)
	- 读取到配置文件后传入SqlSessionFactoryBuilder，内部使用XMLConfigBuilder的parse方法读取配置并set到一个configuration变量中返回一个Configuration对象
	- ![image.png](../assets/image_1714228148958_0.png)
	- 使用build方法创建一个DefaultSqlSessionFactory并返回
	- 在其中会创建一个SqlSession，其中会创建事务工厂之类的
	- ![image.png](../assets/image_1714228719703_0.png)
	- 将mapper类传入session，通过session.getMapper方法在mapperRegistry获取到一个该mapper类的代理类MapperProxy
	- 执行时会执行该代理类的invoke方法
	- ![image.png](../assets/image_1714230626595_0.png)
	- 触发mapperMethod的execute方法
	- ```java
	  public Object execute(SqlSession sqlSession, Object[] args) {
	    Object result;
	    switch (command.getType()) {
	      case *INSERT*: {
	        Object param = method.convertArgsToSqlCommandParam(args);
	        result = rowCountResult(sqlSession.insert(command.getName(), param));
	        break;
	      }
	      case *UPDATE*: {
	        Object param = method.convertArgsToSqlCommandParam(args);
	        result = rowCountResult(sqlSession.update(command.getName(), param));
	        break;
	      }
	      case *DELETE*: {
	        Object param = method.convertArgsToSqlCommandParam(args);
	        result = rowCountResult(sqlSession.delete(command.getName(), param));
	        break;
	      }
	      case *SELECT*:
	        if (method.returnsVoid() && method.hasResultHandler()) {
	          executeWithResultHandler(sqlSession, args);
	          result = null;
	        } else if (method.returnsMany()) {
	          result = executeForMany(sqlSession, args);
	        } else if (method.returnsMap()) {
	          result = executeForMap(sqlSession, args);
	        } else if (method.returnsCursor()) {
	          result = executeForCursor(sqlSession, args);
	        } else {
	          Object param = method.convertArgsToSqlCommandParam(args);
	          result = sqlSession.selectOne(command.getName(), param);
	          if (method.returnsOptional()
	              && (result == null || !method.getReturnType().equals(result.getClass()))) {
	            result = Optional.*ofNullable*(result);
	          }
	        }
	        break;
	      case *FLUSH*:
	        result = sqlSession.flushStatements();
	        break;
	      default:
	        throw new BindingException("Unknown execution method for: " + command.getName());
	    }
	    if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
	      throw new BindingException("Mapper method '" + command.getName()
	          + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
	    }
	    return result;
	  }
	  ```
	- 会根据不同的语句类型执行不同的execute方法，查询list会执行executeForMany方法
	- ```java
	  private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {
	    List<E> result;
	    Object param = method.convertArgsToSqlCommandParam(args);
	    if (method.hasRowBounds()) {
	      RowBounds rowBounds = method.extractRowBounds(args);
	      result = sqlSession.selectList(command.getName(), param, rowBounds);
	    } else {
	      result = sqlSession.selectList(command.getName(), param);
	    }
	    *// issue #510 Collections & arrays support
	  *  if (!method.getReturnType().isAssignableFrom(result.getClass())) {
	      if (method.getReturnType().isArray()) {
	        return convertToArray(result);
	      } else {
	        return convertToDeclaredCollection(sqlSession.getConfiguration(), result);
	      }
	    }
	    return result;
	  }
	  ```
	- selectList获取MappedStatement，再执行executor.query方法
	- ```java
	  @Override
	  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);
	  }
	  ```
	- BoundSql为去掉if，where标签的sql语句，Cachekey为缓存key
	- 查询时先从缓存获取，获取不到或list为null就执行delegate.query方法查询
	- 检查executor是否被关闭，是否清理缓存
	- 通过queryFromDatabase，先在缓存中放一个占位符，接着使用doQuery方法查询，然后把缓存中的占位符换成真正的结果
	- ```java
	  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 {
	      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;
	  }
	  ```
	- 执行doQuery方法，为BatchExecutor类的方法
	- ```java
	  public <E> List<E> doQuery(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
	      throws SQLException {
	    Statement stmt = null;
	    try {
	      flushStatements();
	      Configuration configuration = ms.getConfiguration();
	      StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameterObject, rowBounds, resultHandler, boundSql);
	      Connection connection = getConnection(ms.getStatementLog());
	      stmt = handler.prepare(connection, transaction.getTimeout());
	      handler.parameterize(stmt);
	      return handler.query(stmt, resultHandler);
	    } finally {
	      closeStatement(stmt);
	    }
	  }
	  ```
	- 通过Statement执行静态语句获取结果
	- 执行的是PrepareStatementHandler.query方法，获取结果后交给ResultSetHandler处理，通过resultMap将值赋值给对象