<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css" rel="external nofollow" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js"></script> 

<!-- select2 -->
<link rel="stylesheet" type="text/css" href="${ctx}/common/select2/css/select2.css" rel="external nofollow" />
<script type="text/javascript" src="${ctx}/common/select2/js/select2.full.js"></script>
<!-- 中文国际化还需要进行参数设置 -->
<script type="text/javascript" src="${ctx}/common/select2/js/i18n/zh-CN.js"></script>

<select name="parentid" class="js-data-example-ajax" href="${ctx}/member/loadMembersInfo.do?uid=${mem.uid}" rel="external nofollow" style="width:400px" inputMessage="请输入会员编号(可部分匹配)">
 <option selected="selected" value="666">沉默王二</option>
</select>

<script type="text/javascript">
 $(function() {
  $("select.js-data-example-ajax").each(
  function() {
   var $this = $(this);
   $this.select2({
    language : "zh-CN",// 指定语言为中文，国际化才起效
    inputMessage : $this.attr("inputMessage"),// 添加默认参数
    ajax : {
     url : $this.attr("href"),
     dataType : 'json',
     delay : 250,// 延迟显示
     data : function(params) {
      return {
       username : params.term, // 搜索框内输入的内容，传递到Java后端的parameter为username
       page : params.page,// 第几页，分页哦
       rows : 10// 每页显示多少行
      };
     },
     // 分页
     processResults : function(data, params) {
      params.page = params.page || 1;
      return {
       results : data.data,// 后台返回的数据集
       pagination : {
        more : params.page < data.total// 总页数为10，那么1-9页的时候都可以下拉刷新
       }
      };
     },
     cache : false
    },
    escapeMarkup : function(markup) {
     return markup;
    }, // let our custom formatter work
    minimumInputLength : 1,// 最少输入一个字符才开始检索
    templateResult : function(repo) {// 显示的结果集格式，这里需要自己写css样式，可参照demo
     // 正在检索
     if (repo.loading)
      return repo.text;
     var markup = repo.username;
     markup += repo.realname;
     var markup = "<div class='select2-result-repository clearfix'>" + "<div class='select2-result-repository__avatar'><img src='"
       + repo.headimgUrl + "' /></div>" + "<div class='select2-result-repository__meta'>"
       + "<div class='select2-result-repository__title'>" + repo.username + "</div>";
     if (repo.realname) {
      markup += "<div class='select2-result-repository__description'>" + repo.realname + "</div>";
     }
     markup += "<div class='select2-result-repository__statistics'>"
       + "<div class='select2-result-repository__forks'><i class='fa fa-user'></i> 下级会员数" + repo.children_count + " </div>"
       + "</div>" + "</div></div>";
     return markup;
    }, 
    templateSelection : function(repo) {
     return repo.realname || repo.text;
    }// 列表中选择某一项后显示到文本框的内容
   });
  });
 });
</script>

@RequestMapping(value = "loadMembersInfo")
public void loadMembersInfo(HttpServletRequest request, HttpServletResponse response) throws IOException {
 Integer uid = StrUtil.parseStringToInt(request.getParameter("uid"));
 Members mem = this.memberService.selectByPrimaryKey(uid);
 // 分页参数的转换，需要和前台select2进行匹配，下文放代码
 BaseConditionVO vo = getBaseConditionVOForTable(request);
 vo.addParams("username", StrUtil.getUTF8String(request.getParameter("username")));
 vo.addParams("uid", uid);
 // 封装结果集，和前台select2也是匹配的。
 PageGrid page = createPageGrid(this.membersMapper.getPromoterList(vo, vo.createRowBounds()), vo,
   this.membersMapper.searchPromoterTotalCount(vo));
 // 以json格式写入到response
 out(page, response);
}

BaseConditionVO.Java
public class BaseConditionVO {
 public final static int PAGE_SHOW_COUNT = 50;
 private int pageNum = 1;
 private int numPerPage = 0;
 private int totalCount = 0;
 private String orderField;
 private String orderDirection;
 /**
  * @Fields ps : 对参数类型进行封装.
  */
 private Map<String, Object> mo = new HashMap<String, Object>();
 public int getPageNum() {
  return pageNum;
 }
 public void setPageNum(int pageNum) {
  this.pageNum = pageNum;
 }
 public int getNumPerPage() {
  return numPerPage > 0 ? numPerPage : PAGE_SHOW_COUNT;
 }
 public void setNumPerPage(int numPerPage) {
  this.numPerPage = numPerPage;
 }
 public String getOrderField() {
  return orderField;
 }
 public void setOrderField(String orderField) {
  this.orderField = orderField;
 }
 public String getOrderDirection() {
  return "desc".equals(orderDirection) ? "desc" : "asc";
 }
 public void setOrderDirection(String orderDirection) {
  this.orderDirection = orderDirection;
 }
 public int getTotalCount() {
  return totalCount;
 }
 public void setTotalCount(int totalCount) {
  this.totalCount = totalCount;
 }
 public int getStartIndex() {
  int pageNum = this.getPageNum() > 0 ? this.getPageNum() - 1 : 0;
  return pageNum * this.getNumPerPage();
 }
 public RowBounds createRowBounds() {
  RowBounds ro = new RowBounds(this.getStartIndex(), this.getNumPerPage());
  return ro;
 }
 /**
  * @Title: addParams
  * @Description: 添加查询条件
  * @param key
  * @param value
  */
 public void addParams(String key, Object value) {
  this.getMo().put(key, value);
 }
 /** 
 * @Title: getParams 
 * @Description: 获取查询条件
 * @param key
 * @return
 */
 public Object getParams(String key) {
  return this.getMo().get(key);
 }
 /**
  * @return the mo
  */
 public Map<String, Object> getMo() {
  return mo;
 }
 /**
  * @param mo
  *   the mo to set
  */
 public void setMo(Map<String, Object> mo) {
  this.mo = mo;
 }
}

protected BaseConditionVO getBaseConditionVOForTable(HttpServletRequest req) {
 BaseConditionVO vo = new BaseConditionVO();
 // 当前页
 int currentPage = StrUtil.parseStringToInt(req.getParameter("page"));
 // 一页显示多少行
 int sizes = StrUtil.parseStringToInt(req.getParameter("rows"));
 // 排序
 String sortOrder = StrUtil.getString(req.getParameter("sord"));
 String sortCol = StrUtil.getString(req.getParameter("sidx"));
 vo.setNumPerPage(sizes);
 vo.setPageNum(currentPage);
 vo.setOrderField(sortCol);
 vo.setOrderDirection(sortOrder);
 return vo;
}

@XStreamAlias("pageGrid")
@SuppressWarnings("rawtypes")
public class PageGrid {
 private int page;
 // 总页数，和select2的processResults.pagination匹配
 private int total;
 private int records;
 // 数据结果集，和select2的processResults.results匹配
 private List data;
 public int getPage() {
  return this.page;
 }
 public void setPage(int page) {
  this.page = page;
 }
 public int getTotal() {
  return this.total;
 }
 public void setTotal(int total) {
  this.total = total;
 }
 public int getRecords() {
  return this.records;
 }
 public void setRecords(int records) {
  this.records = records;
 }
 public List getData() {
  return this.data;
 }
 public void setData(List data) {
  this.data = data;
 }
}

protected PageGrid createPageGrid(List list, BaseConditionVO vo, int searchTotalCount) {
 PageGrid pageGrid = new PageGrid();
 // 数据
 pageGrid.setData(list);
 // 当前页
 pageGrid.setPage(vo.getPageNum());
 // 总数目
 pageGrid.setRecords(list.size());
 // 总页数
 int total = 0;
 if (pageGrid.getRecords() != 0) {
  total = searchTotalCount % vo.getNumPerPage() == 0 ? searchTotalCount / vo.getNumPerPage()
    : searchTotalCount / vo.getNumPerPage() + 1;
 }
 pageGrid.setTotal(total);
 return pageGrid;
}

List getPromoterList(BaseConditionVO vo, RowBounds createRowBounds);

<select id="getPromoterList" resultType="hashmap" parameterType="map">
 select
 m.uid as id,
 convert(m.username,char) username,
 m.realname,
 m.children_count,
 m.headimgUrl
 from
 members m
 where m.deleteflag=0
 <if test="mo.username != ''">and m.username like CONCAT('%', '${mo.username}', '%')</if>
 <choose>
  <when test="orderField !=null and orderField !=''">
   ORDER BY ${orderField}
   <if test="orderDirection != null and orderDirection != ''">${orderDirection}</if>
  </when>
  <otherwise>
   order by m.username DESC
  </otherwise>
 </choose>
</select>

int searchPromoterTotalCount(BaseConditionVO vo);

<select id="searchPromoterTotalCount" resultType="java.lang.Integer" parameterType="map">
 select count(0) as a
 from
 members m
 where m.deleteflag=0 
 <if test="mo.username != ''">and m.username like CONCAT('%', '${mo.username}', '%')</if>
</select>

protected void out(Object result, HttpServletResponse response) throws IOException {
 ServletOutputStream out = response.getOutputStream();
 ObjectMapper objectMapper = new ObjectMapper();
 objectMapper.writeValue(out, result);
 out.flush();
}

 Results.prototype.option = function (data) {
 var option = document.createElement('li');
 option.className = 'select2-results__option';
 var attrs = {
  'role': 'treeitem',
  'aria-selected': 'false'
 };
 if (data.disabled) {
  delete attrs['aria-selected'];
  attrs['aria-disabled'] = 'true';
 }
// id为空的情况下，删除的aria-selected，而aria-selected恰好又是列表选中的关键属性。
// 这个就是个坑，只能这么说，select2给出的api上完全不讲这点，我去！！！！！！！
 if (data.id == null) {
  delete attrs['aria-selected'];
 }
 ......
}

S2.define('select2/data/minimumInputLength',[
], function () {
 function MinimumInputLength (decorated, $e, options) {
 this.minimumInputLength = options.get('minimumInputLength');
 // inputMessage
 this.inputMessage = options.get('inputMessage');
 decorated.call(this, $e, options);
 }
 MinimumInputLength.prototype.query = function (decorated, params, callback) {
 params.term = params.term || '';
 if (params.term.length < this.minimumInputLength) {
  this.trigger('results:message', {
  message: 'inputTooShort',
  args: {
   minimum: this.minimumInputLength,
   input: params.term,
   inputMessage : this.inputMessage, // inputMessage，传递给i18n
   params: params
  }
  });
  return;
 }
 decorated.call(this, params, callback);
 };
 return MinimumInputLength;
});

 this.defaults = {
 ...
  minimumInputLength: 0,
  inputMessage: '',
  maximumInputLength: 0,
  ...
 };

inputTooShort : function(e) {
 if (e.inputMessage) {
  return e.inputMessage;// 增加inputMessage
 } else {
  var t = e.minimum - e.input.length, n = "请再输入至少" + t + "个字符";
  return n
 }
},