mybatis-plus根据指定字段批量，删除、修改实现过程

// 这种方法就是把mybatis的活在干一遍,还是一条一条处理的.只是共用一个session连接
@Autowired
private SqlSessionTemplate sqlSessionTemplate;

// 新获取一个模式为BATCH，自动提交为false的session
SqlSession session = sqlSessionTemplate.getSqlSessionFactory().openSession(ExecutorType.BATCH,false);
static final BATCH_SIZE = 1000;
// XxxMapper 为 对应的mapper文件
XxxMapper xxMapper = session.getMapper(XxxMapper.class);
int size = updateList.size();
try {
    for(int i=0; i < size; i++) {
    	// updateByXxx 写好的单条数据的方法
        xxMapper.updateByXxx(updateList.get(i));
        if(i % BATCH_SIZE == 0 || i == size-1){
            //手动每1000个一提交，提交后无法回滚
            session.commit();
            //清理缓存，防止溢出
            session.clearCache();
        }
    }
}catch (Exception e) {
    session.rollback();
} finally {
    session.close();
}

	// mybatis plus 源码
    @Transactional(rollbackFor = Exception.class)
    @Override
    public boolean updateBatchById(Collection<T> entityList, int batchSize) {
        String sqlStatement = getSqlStatement(SqlMethod.UPDATE_BY_ID);
        return executeBatch(entityList, batchSize, (sqlSession, entity) -> {
            MapperMethod.ParamMap<T> param = new MapperMethod.ParamMap<>();
            param.put(Constants.ENTITY, entity);
            sqlSession.update(sqlStatement, param);
        });
    }

//删除方法 deleteList  是要删除的主键list
List<String> deleteList = new ArrayList<>();
dao.batchDelete(deleteList, delete -> new QueryWrapper<String>().eq("xx", delete));

// 修改方法 OBJ 代码表对象
List<OBJ> updateList = new ArrayList<>();
dao.batchUpdate(updateList, update -> new LambdaQueryWrapper<OBJ>()
                        .eq(OBJ::getProductId, update.getProductId()));

    boolean batchUpdate(List<OBJ> updateList, Function<OBJ, LambdaQueryWrapper> queryWrapperFunction);

    boolean batchDelete(List<String> deleteList, Function<String, QueryWrapper> queryWrapperFunction);

	@Override
    public boolean batchUpdate(List<OBJ> entityList, Function<OBJ, LambdaQueryWrapper> function) {
        return this.executeBatch(entityList, DEFAULT_BATCH_SIZE, (sqlSession, entity) -> {
            ParamMap param = new ParamMap();
            param.put(Constants.ENTITY, entity);
            param.put(Constants.WRAPPER, function.apply(entity));
            sqlSession.update(this.getSqlStatement(SqlMethod.UPDATE), param);
        });
    }

    @Override
    public boolean batchDelete(List<String> deleteList, Function<String, QueryWrapper> function) {
        return this.executeBatch(deleteList, DEFAULT_BATCH_SIZE, (sqlSession, entity) -> {
            ParamMap param = new ParamMap();
            param.put(Constants.ENTITY, entity);
            param.put(Constants.WRAPPER, function.apply(entity));
            sqlSession.delete(this.getSqlStatement(SqlMethod.DELETE), param);
        });
    }
	// 也可以传入一个LambdaUpdateWrapper 来制定更新
    @Override
    public boolean batchUpdate2(List<ContProductAbstractLocalDO> entityList, Function<ContProductAbstractLocalDO, LambdaUpdateWrapper> function) {
        return this.executeBatch(entityList, DEFAULT_BATCH_SIZE, (sqlSession, entity) -> {
            ParamMap param = new ParamMap();
            param.put(Constants.ENTITY, null);
            param.put(Constants.WRAPPER, function.apply(entity));
            sqlSession.update(this.getSqlStatement(SqlMethod.UPDATE), param);
        });
    }
示例 : 指定执行的SQL 和字段
   private LambdaUpdateWrapper<OBJ> getUpdateWrapper(OBJupdate) {
        retur new LambdaUpdateWrapper<OBJ>()
                .eq(OBJ::getxx, update.xx())
                .set(OBJ::getxxx, update.xxxx());