public void setColumnNames(String columnNames) {
		String[] names = StringUtils.tokenizeToStringArray(columnNames, ",");
		for (String name : names) {
			this.columnNames.add(name.trim());
		}
	}
Transforms a payload to a Map representation based on provided column names.

TODO: Right now it simply supports full payload under a 'payload' key or a JSON string with values stored with keys
corresponding to the column names specified. This could be expanded for additional payload types

@author Thomas Risberg
@author Gary Russell
@since 1.0
extensions/spring-xd-extension-jdbc/src/main/java/org/springframework/xd/jdbc/JdbcMessagePayloadTransformer.java