解决Ajax返回数据包含整个jsp页面的问题

<%
    ResultSet rs = conn.executeQuery("select name from tb_book order by id desc");
    String str = "";
    str = "{ "info":"";
    if(rs.next()){
        do{
            str += ""+rs.getString(1)+"";
        }while(rs.next());
    }else{
        str += "暂无图书信息";
    }
    str += "" }";
    out.clear();  // 清除前面的html标签
    out.print(str);
    out.close(); // 清除后面的html标签
%>

发起请求页：

<script>
window.onload=function(){
    new AjaxRequest({
        url:"getInfo.jsp?nocache="+new Date().getTime(),type:"GET",dataType:‘json‘,success:function(data){
            document.getElementById("showInfo").innerHTML = data.info;
        },error:function(err){
            document.getElementById("showInfo").innerHTML = err.status + ":" + err.statusText;
        }
    });
}
</script>
<div id="showInfo"></div>

自定义封闭ajax脚本函数：

var AjaxRequest = function(obj){
    this.req = new XMLHttpRequest();
    this.req.open(obj.type,obj.url,true);
    if(obj.type=="POST"){
        this.req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    }
    this.req.send();
    this.req.onreadystatechange = function(){
        if(this.req.readyState==4){
            if(this.req.status==200){
                if(obj.dataType==‘json‘){
                    obj.success(JSON.parse(this.req.responseText));
                }else{
                    obj.success(this.req.responseText);
                }
            }else{
                obj.error({status:this.req.status,statusText:this.req.statusText});
            }
        }
    }.bind(this);
}