怎么用struts2标签循环双层List并分组

public class Agent implements java.io.Serializable {    // Fields    private Integer agtId;    private String agtName;    private String agtActNum;    private Timestamp agtJoin;    private String agtAdd1;    private String agtAdd2;    private Integer agtSales;    private String agtCity;    private String agtState;    private String agtZip;    private String agtCountry;    private String agtSalute;    private String agtFname;    private String agtLname;    private String agtTitle;    private String agtPhone;    private String agtMobile;    private String agtFax;    private String agtEmail;    private String agtUrl;    private Short status;    private Timestamp createDate;    private Timestamp lastMod;    private String modBy;    private Integer languageId;    private Integer yearEstablished;    private String emergencyNumber;    private Boolean qualified;    private Timestamp qualifiedDate;    private String area;    private Timestamp lastBookedOnline;    private String agtNameChinese;    private String agtPhone2;    private Integer creditRatingId;    private Integer agtIdAccounting;    private Timestamp lastModAccounting;    private String agtCcemail;    private Integer employeeRegionId;    private Integer employeeRegionArea;    private Integer engEmployeeRegionId;    private String accessTourType;    private Boolean isExternalOp;    private Boolean unsubscribe;    private Integer agtCityId;}