struts2 与ajax 通过stream类型返回字符串

private InputStream hint;
public String modifyName() throws Exception{
Language lan=languageService.getById(model.getId());
lan.setName(model.getName());
languageService.merge(lan);
this.hint= new StringBufferInputStream(transcoding("成功"));
return "hint";
}
public InputStream getHint() {
return hint;
}
public void setHint(InputStream hint) {
this.hint = hint;
}
private String transcoding(String str) {
try {
return new String(str.getBytes("utf-8"), "iso-8859-1");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return str;
}

<result name="hint" type="stream">
<param name="contentType">text/html</param>
<param name="inputName">hint</param>
</result>

$.ajax({
async : false,
cache : false,
type : 'POST',
//dataType : "json",
url : 'categoryManage_modifyName.action',
data : {
id:treeNode.id,
name:treeNode.name
},
success : function(data) {
$.messager.alert('消息提示',  data);
return true;
},
error : function() {
$.messager.alert('消息提示','请求失败!','error');
return false;
}});