liquibase-core/src/main/java/liquibase/changelog/ChangeLogParameters.java
public Object getValue(String key, DatabaseChangeLog changeLog) {
        ChangeLogParameter parameter = findParameter(key, changeLog);
        return (parameter != null) ? parameter.getValue() : null;
    }
public Object getValue(String key, DatabaseChangeLog changeLog) {
        ChangeLogParameter parameter = findParameter(key, changeLog);
        return (parameter != null) ? parameter.getValue() : null;
    }
Return the value of a parameter

@param key Name of the parameter
@return The parameter value or null if not found. (Note that null can also be return if it is the parameter
value. For strict parameter existence use {@link #hasValue(String, DatabaseChangeLog)}