bson/src/main/org/bson/BasicBSONObject.java
public String getString(final String key) {
        Object foo = get(key);
        if (foo == null) {
            return null;
        }
        return foo.toString();
    }
public String getString(final String key) {
        Object foo = get(key);
        if (foo == null) {
            return null;
        }
        return foo.toString();
    }
Returns the value of a field as a string

@param key the field to look up
@return the value of the field, converted to a string