我可以用jqGrid实现延迟加载吗？ [英] Can I implement lazy loading with jqGrid?

问题描述

我有一个包含超过5000条数据记录的网格。这些数据每天都在增长。当我使用网格加载页面时，在网格显示数据之前需要差不多一分钟，我必须一次显示10行。

I have a grid with over 5000 data records. This data keeps growing on a daily basis. When I load the page with the grid, it takes almost a minute before the grid shows the data which I have to display 10 rows at a time.

是否可能用这个jqGrid实现延迟加载？

Is it possible then to implement lazy loading with this jqGrid?

这是我生成JSon字符串的动作：

This is my action to generate the JSon String:

@RequestMapping(value = "studentjsondata", method = RequestMethod.GET)
public @ResponseBody String studentjsondata(HttpServletRequest httpServletRequest) {
    Format formatter = new SimpleDateFormat("MMMM dd, yyyy");
    String column = "id";
    if(httpServletRequest.getParameter("sidx") != null){
        column = httpServletRequest.getParameter("sidx");
    }
    String orderType = "DESC";
    if(httpServletRequest.getParameter("sord") != null){
        orderType = httpServletRequest.getParameter("sord").toUpperCase();
    }
    int page = 1;
    if(Integer.parseInt(httpServletRequest.getParameter("page")) >= 1){
        page = Integer.parseInt(httpServletRequest.getParameter("page"));
    }
    int limitAmount = 10;
    int limitStart = limitAmount*page - limitAmount;
    List<Student> students = Student.findAllStudentsOrderByColumn(column,orderType,limitStart,limitAmount).getResultList();  
    List<Student> countStudents = Student.findAllStudents();
    double tally = Math.ceil(countStudents.size()/10.0d);
    int totalPages = (int)tally;
    int records = countStudents.size();


    StringBuilder sb = new StringBuilder();
    sb.append("{\"page\":\"").append(page).append("\", \"records\":\"").append(records).append("\", \"total\":\"").append(totalPages).append("\", \"rows\":[");
    boolean first = true;
    for (Student s: students) {
        sb.append(first ? "" : ",");
        if (first) {
            first = false;
        }
        sb.append(String.format("{\"id\":\"%s\", \"cell\":[\"%s\", \"%s\", \"%s\", \"%s\", \"%s\", \"%s\"]}",s.getId(), s.getId(), s.getFirstName(), s.getLastName(),  formatter.format(s.getDateOfBirth().getTime()), s.getGender(), s.getMaritalStatus()));
    }
    sb.append("]}");
    return sb.toString();
}

这是带有jqGrid的页面：

And this is page with the jqGrid:

$("#studentGrid").jqGrid({
            url: '/starburst/programmes/studentjsondata',
            datatype: 'json',
            height: 'auto',
            colNames:['id','First Name', 'Last Name', 'Date Of Birth', 'Gender', 'Marital Status'], 
            colModel:[ 
                {name:'id',index:'id', width:15}, 
                {name:'firstName',index:'firstName', width:30, formoptions:{elmprefix:'(*) '}, editable:true, edittype: 'text', editrules:{required:true}},
                {name:'lastName',index:'lastName', width:30, formoptions:{elmprefix:'(*) '}, editable:true, edittype: 'text',editrules:{required:true}},
                {name:'dateOfBirth',index:'dateOfBirth', width:30, formoptions:{elmprefix:'(*) '},editrules:{required:true}, editable:true, edittype: 'text',               
                    editoptions: {
                        dataInit: function(element) {
                            $(element).datepicker({dateFormat: 'MM dd, yy'})
                        }
                    } 
                },                    
                {name:'gender',index:'gender', width:30, formoptions:{elmprefix:'(*) '}, editable:true, editrules:{required:true}, edittype: 'select',
                    editoptions:{value:{}}
                },
                {name:'maritalStatus',index:'maritalStatus', width:30, formoptions:{elmprefix:'(*) '}, editable:true, editrules:{required:true}, edittype: 'select',
                    editoptions:{value:{}}
                }                    
            ],
            rowNum:10,
            autowidth: true,
            pager: '#pager', 
            sortname: 'id', 
            viewrecords: true, 
            sortorder: "desc",
            caption:"Students",
            emptyrecords: "Empty Records",
            subGrid: true,
            /* <![CDATA[ */ 
            onSelectRow: function(id){ 
                if((lastsel != 0)&&(id!==lastsel)){ 
                    $("#studentGrid").jqGrid('collapseSubGridRow', lastsel);                
                } 
                lastsel=id; 
            }/* ]]> */ 
        });
        $("#studentGrid").jqGrid('navGrid', "#pager", {edit:false,add:false,del:false,search:true},{ },{ },{ },
        { 
            sopt:['eq', 'ne', 'lt', 'gt', 'cn', 'bw', 'ew'],
            closeOnEscape: true, 
            multipleSearch: true, 

请参阅下面的查询：

public static TypedQuery<tt.edu.sbcs.model.Student> findAllStudentsOrderByColumn(String column, String orderType, int limitStart, int limitAmount) {
    EntityManager em = Programme.entityManager();
    TypedQuery<Student> q = em.createQuery("SELECT o FROM Student AS o ORDER BY"+" "+column+" "+orderType, Student.class);
    q.setFirstResult(limitStart);//used to skip the first "N"  elements form the result set, it indexes results form zero 
    q.setMaxResults(limitAmount);
    return q;
}

我在行动abov中设定的限额e。这个值是10.

The limit amount i set in the action above. this value is 10.

推荐答案

好的，所以这里是基于JPA的部分答案（但我想它应该是使它适应Hibernate几乎是微不足道的）。你应该能够做这样的事情来获取必要的对象：

OK, so here is a partial answer based on JPA (but I guess that it should be almost trivial to adapt it to Hibernate). You should be able to do something like this to fetch only the necessary objects :

Query query = em.createQuery("select o from " + "Student"+ " as o order by o.id");
query.setFirstResult(start);
query.setMaxResults(end - start);
return query.getResultList();

对于计数，这样的事情应该这样做：

For a count, something like this should do it:

Number count = (Number) em.createQuery("select count(id) from " + "Student").getSingleResult();
if (count == null) {
    count = Integer.valueOf(0);
}
return count.intValue();

当我有更多信息时会进行编辑。

Will edit when I have more info.

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