我正在尝试使用$ .ajax()方法动态填充多个selectbox .... 这是我的HTML代码......
<select id="imageSize" name="ImageSizeId"></select>
<select id="circulation" name="circulationId"></select>
这是我的servlet代码.....
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/json;charset=utf-8");
response.setHeader("Cache-Control", "no-cache");
PrintWriter out = response.getWriter();
JSONObject usesfactors = new JSONObject();
JSONArray jArraysize = new JSONArray();
JSONArray jArraycirculation = new JSONArray();
Statement stmtsize,stmtcirculation;
ResultSet rssize,rscirculation;
int category_id = Integer.parseInt(request.getParameter("CategoryId"));
int format_id = Integer.parseInt(request.getParameter("FormatId"));
String size,display,des;
int sizeid;
try {
if(category_id == 2 && format_id == 201){
// Get image size factors
String sql1="SELECT SizeId,Size FROM Size WHERE Category_id = "+category_id+" AND Format_id = "+format_id+" ";
PreparedStatement ps1 = conn.prepareStatement(sql1);
rssize = ps1.executeQuery() ;
if( rssize!=null){
System.out.println("Not Null");// its printing even if resultset rssize has no records.......why?
while(rssize.next())
{
System.out.println("inside resultset");
JSONObject jobj = new JSONObject();
sizeid = rssize.getInt("SizeId");
size=rssize.getString("Size");
System.out.println(size);
jobj.put("SizeId", sizeid);
jobj.put("Size", size);
jArraysize.add(jobj);
}
usesfactors.put("Size", jArraysize);
rssize.close();
}
else{
System.out.println("Does not have Size factors");
}
// Get image circulation factors
String sql2="SELECT circulationId,circulation FROM Circulation WHERE Category_id = "+category_id+" AND Format_id = "+format_id+" ";
PreparedStatement ps2 = conn.prepareStatement(sql2);
rscirculation = ps2.executeQuery() ;
if(rscirculation!=null){
while(rscirculation.next())
{
JSONObject jobj = new JSONObject();
display = rscirculation.getString("DisplayName");
des=rscirculation.getString("Description");
jobj.put("DisplayName", display);
jobj.put("Description", des);
jArraycirculation.add(jobj);
}
usesfactors.put("Circulation", jArraycirculation);
rscirculation.close();
}
else{
System.out.println("Does not have Circulation factors");
}
out.println(usesfactors);
}
我得到空的json结果....?错了? { “大小”:[], “循环”:[]} 我不想执行这个stmt“usesfactors.put(”Size“,jArraysize);”如果resultset rssize为null但是这个stmt正在执行,即使结果集rssize没有记录.... 总之,我想将json数组(jArraysize)放在json对象(usesfactors)中,当且仅当结果集rssize有记录时。
答案 0 :(得分:0)
The problem in your code might be your sql queries which are not returning any values.because i have done in my IDE in the same way you have done,only difference is that instead of getting values from database i have kept manually by iterating for loop.below is the code...
JSONObject usesfactors = new JSONObject();
JSONArray jArraysize = new JSONArray();
JSONArray jArraycirculation = new JSONArray();
for(int i=0;i<3;i++)
{
JSONObject jobj = new JSONObject();
jobj.put("SizeId", "1");
jobj.put("Size", "2");
jArraysize.put(jobj);
}
usesfactors.put("Size", jArraysize);
for(int i=0;i<3;i++)
{
JSONObject jobj = new JSONObject();
jobj.put("DisplayName", "3");
jobj.put("Description", "4");
jArraycirculation.put(jobj);
}
usesfactors.put("Circulation", jArraycirculation);
System.out.println(usesfactors);
答案 1 :(得分:0)
在回答代码中有关其进入rssize!=null
块的原因的问题时,请参阅javadoc on executeQuery。它明确声明它永远不会返回null,因此null检查总是通过。这意味着空结果集将跳过该部分中的循环,但仍然按
usesfactors.put("Size", jArraysize);
这应该被重写以实际避免在空返回集上插入。应该进行类似的更改以纠正循环部分,这也会进行无效的无效检查。
while(rssize.next())
{
System.out.println("inside resultset");
JSONObject jobj = new JSONObject();
sizeid = rssize.getInt("SizeId");
size=rssize.getString("Size");
System.out.println(size);
jobj.put("SizeId", sizeid);
jobj.put("Size", size);
jArraysize.add(jobj);
}
if (jArraysize.length > 0)
{
usesfactors.put("Size", jArraysize);
}
else
{
System.out.println("Does not have Size factors");
}
rssize.close();