insert，返回值是：新插入行的主键（primary key）；需要包含语句，才会返回主键，否则返回值为null。

关于ibatis的接口，参见其源码（com\ibatis\sqlmap\client\SqlMapExecutor.java）:

/*  *  Copyright 2004 Clinton Begin  *  *  Licensed under the Apache License, Version 2.0 (the "License");  *  you may not use this file except in compliance with the License.  *  You may obtain a copy of the License at  *  *      http://www.apache.org/licenses/LICENSE-2.0  *  *  Unless required by applicable law or agreed to in writing, software  *  distributed under the License is distributed on an "AS IS" BASIS,  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  *  See the License for the specific language governing permissions and  *  limitations under the License.  */  package com.ibatis.sqlmap.client;    import com.ibatis.common.util.PaginatedList;  import com.ibatis.sqlmap.client.event.RowHandler;  import com.ibatis.sqlmap.engine.execution.BatchException;    import java.sql.SQLException;  import java.util.List;  import java.util.Map;    /**  * This interface declares all methods involved with executing statements  * and batches for an SQL Map.  *  * @see SqlMapSession  * @see SqlMapClient  */  public interface SqlMapExecutor {      /**    * Executes a mapped SQL INSERT statement.    * Insert is a bit different from other update methods, as it    * provides facilities for returning the primary key of the    * newly inserted row (rather than the effected rows).  This    * functionality is of course optional.    * 
    * The parameter object is generally used to supply the input    * data for the INSERT values.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @return The primary key of the newly inserted row.  This might be automatically    *         generated by the RDBMS, or selected from a sequence table or other source.    * @throws java.sql.SQLException If an error occurs.    */    Object insert(String id, Object parameterObject) throws SQLException;      /**    * Executes a mapped SQL INSERT statement.    * Insert is a bit different from other update methods, as it    * provides facilities for returning the primary key of the    * newly inserted row (rather than the effected rows).  This    * functionality is of course optional.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @return The primary key of the newly inserted row.  This might be automatically    *         generated by the RDBMS, or selected from a sequence table or other source.    * @throws java.sql.SQLException If an error occurs.    */    Object insert(String id) throws SQLException;      /**    * Executes a mapped SQL UPDATE statement.    * Update can also be used for any other update statement type,    * such as inserts and deletes.  Update returns the number of    * rows effected.    * 
    * The parameter object is generally used to supply the input    * data for the UPDATE values as well as the WHERE clause parameter(s).    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @return The number of rows effected.    * @throws java.sql.SQLException If an error occurs.    */    int update(String id, Object parameterObject) throws SQLException;      /**    * Executes a mapped SQL UPDATE statement.    * Update can also be used for any other update statement type,    * such as inserts and deletes.  Update returns the number of    * rows effected.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @return The number of rows effected.    * @throws java.sql.SQLException If an error occurs.    */    int update(String id) throws SQLException;      /**    * Executes a mapped SQL DELETE statement.    * Delete returns the number of rows effected.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the DELETE statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @return The number of rows effected.    * @throws java.sql.SQLException If an error occurs.    */    int delete(String id, Object parameterObject) throws SQLException;      /**    * Executes a mapped SQL DELETE statement.    * Delete returns the number of rows effected.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @return The number of rows effected.    * @throws java.sql.SQLException If an error occurs.    */    int delete(String id) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a single object instance.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @return The single result object populated with the result set data,    *         or null if no result was found    * @throws java.sql.SQLException If more than one result was found, or if any other error occurs.    */    Object queryForObject(String id, Object parameterObject) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a single object instance.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @return The single result object populated with the result set data,    *         or null if no result was found    * @throws java.sql.SQLException If more than one result was found, or if any other error occurs.    */    Object queryForObject(String id) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * the supplied result object.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param resultObject    The result object instance that should be populated with result data.    * @return The single result object as supplied by the resultObject parameter, populated with the result set data,    *         or null if no result was found    * @throws java.sql.SQLException If more than one result was found, or if any other error occurs.    */    Object queryForObject(String id, Object parameterObject, Object resultObject) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @return A List of result objects.    * @throws java.sql.SQLException If an error occurs.    */    List queryForList(String id, Object parameterObject) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @return A List of result objects.    * @throws java.sql.SQLException If an error occurs.    */    List queryForList(String id) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects within a certain range.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param skip            The number of results to ignore.    * @param max             The maximum number of results to return.    * @return A List of result objects.    * @throws java.sql.SQLException If an error occurs.    */    List queryForList(String id, Object parameterObject, int skip, int max) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects within a certain range.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @param skip            The number of results to ignore.    * @param max             The maximum number of results to return.    * @return A List of result objects.    * @throws java.sql.SQLException If an error occurs.    */    List queryForList(String id, int skip, int max) throws SQLException;        /**    * Executes a mapped SQL SELECT statement that returns a number of    * result objects that will be handled one at a time by a    * RowHandler.    * 
    * This is generally a good approach to take when dealing with large sets    * of records (i.e. hundreds, thousands...) that need to be processed without    * eating up all of the system resources.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param rowHandler      A RowHandler instance    * @throws java.sql.SQLException If an error occurs.    */    void queryWithRowHandler(String id, Object parameterObject, RowHandler rowHandler) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns a number of    * result objects that will be handled one at a time by a    * RowHandler.    * 
    * This is generally a good approach to take when dealing with large sets    * of records (i.e. hundreds, thousands...) that need to be processed without    * eating up all of the system resources.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @param rowHandler      A RowHandler instance    * @throws java.sql.SQLException If an error occurs.    */    void queryWithRowHandler(String id, RowHandler rowHandler) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects a page at a time.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param pageSize        The maximum number of result objects each page can hold.    * @return A PaginatedList of result objects.    * @throws java.sql.SQLException If an error occurs.    * @deprecated All paginated list features have been deprecated    */    PaginatedList queryForPaginatedList(String id, Object parameterObject, int pageSize) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects a page at a time.    * 
    * This overload assumes no parameter is needed.    *    * @param id              The name of the statement to execute.    * @param pageSize        The maximum number of result objects each page can hold.    * @return A PaginatedList of result objects.    * @throws java.sql.SQLException If an error occurs.    * @deprecated All paginated list features have been deprecated    */    PaginatedList queryForPaginatedList(String id, int pageSize) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects that will be keyed into a Map.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param keyProp         The property to be used as the key in the Map.    * @return A Map keyed by keyProp with values being the result object instance.    * @throws java.sql.SQLException If an error occurs.    */    Map queryForMap(String id, Object parameterObject, String keyProp) throws SQLException;      /**    * Executes a mapped SQL SELECT statement that returns data to populate    * a number of result objects from which one property will be keyed into a Map.    * 
    * The parameter object is generally used to supply the input    * data for the WHERE clause parameter(s) of the SELECT statement.    *    * @param id              The name of the statement to execute.    * @param parameterObject The parameter object (e.g. JavaBean, Map, XML etc.).    * @param keyProp         The property to be used as the key in the Map.    * @param valueProp       The property to be used as the value in the Map.    * @return A Map keyed by keyProp with values of valueProp.    * @throws java.sql.SQLException If an error occurs.    */    Map queryForMap(String id, Object parameterObject, String keyProp, String valueProp) throws SQLException;      /**    * Starts a batch in which update statements will be cached before being sent to    * the database all at once. This can improve overall performance of updates update    * when dealing with numerous updates (e.g. inserting 1:M related data).    *    * @throws java.sql.SQLException If the batch could not be started.    */    void startBatch() throws SQLException;      /**    * Executes (flushes) all statements currently batched.    *    * @return the number of rows updated in the batch    * @throws java.sql.SQLException If the batch could not be executed or if any of the statements    *                               fails.    */    int executeBatch() throws SQLException;      /**    * Executes (flushes) all statements currently batched.    *    * @return a List of BatchResult objects.  There will be one element in the    *  list for each sub-batch executed.  A sub-batch is created by adding a statement    *  to the batch that does not equal the prior statement.     * @throws SQLException if a database access error occurs, or the drive    *   does not support batch statements    * @throws BatchException if the driver throws BatchUpdateException    * @see com.ibatis.sqlmap.engine.execution.BatchException    */    List executeBatchDetailed() throws SQLException, BatchException;  }