【异常】EmptyResultDataAccessException:Incorrect result size: expected 1,actual 0

在使用JdbcTemplate的queryForMap方法，查询数据库时报错。

原因：

查看源码：
"JdbcTemplate"类

public Map<String, Object> queryForMap(String sql, Object[] args, int[] argTypes) throws DataAccessException {
	return queryForObject(sql, args, argTypes, getColumnMapRowMapper());
}

public Map<String, Object> queryForMap(String sql, Object... args) throws DataAccessException {
	return queryForObject(sql, args, getColumnMapRowMapper());
}

public <T> T queryForObject(String sql, Object[] args, RowMapper<T> rowMapper) throws DataAccessException {
	List<T> results = query(sql, args, new RowMapperResultSetExtractor<T>(rowMapper, 1));
	return DataAccessUtils.requiredSingleResult(results);
}

public <T> T queryForObject(String sql, RowMapper<T> rowMapper, Object... args) throws DataAccessException {
	List<T> results = query(sql, args, new RowMapperResultSetExtractor<T>(rowMapper, 1));
	return DataAccessUtils.requiredSingleResult(results);
}

"DataAccessUtils"类

/**
* Return a single result object from the given Collection.
 * <p>Throws an exception if 0 or more than 1 element found.
 * @param results the result Collection (can be <code>null</code>)
 * @return the single result object
 * @throws IncorrectResultSizeDataAccessException if more than one
 * element has been found in the given Collection
 * @throws EmptyResultDataAccessException if no element at all
 * has been found in the given Collection
 */
public static <T> T requiredSingleResult(Collection<T> results) throws IncorrectResultSizeDataAccessException {
	int size = (results != null ? results.size() : 0);
	if (size == 0) {
		throw new EmptyResultDataAccessException(1);
	}
	if (results.size() > 1) {
		throw new IncorrectResultSizeDataAccessException(1, size);
	}
	return results.iterator().next();
}

根据源码得知，使用queryForMap方法或queryForObject方法查询数据库时，如果结果集为空，则会抛出"EmptyResultDataAccessException"异常。如果结果集数量多于1个，则会抛出"IncorrectResultSizeDataAccessException"异常。

解决办法：

添加try/catch，捕获异常