如何将servlet的json输出发送到jsp?

问题描述：

我正在进行库存控制.我试图检查输入的商品数量是否少于库存数量.我正在获取servet json输出.但是我无法将其发送回jsp.

I'm making an inventory control. I was trying to check if the entered quantity of item is less than the stock quantity or not. I'm getting the servet json output. But I can't send it to jsp back.

Jsp JQuery代码.

Jsp JQuery code.

<script>
        $('document').ready(function() {
            $('#submit_btn').click((function() {
                var $name = $("select#item_name").val();
                var $qty = $("input#qty").val();

                $.post('BuyItem', {item_name: $name, item_qty: $qty}, function(data) {
                    if (data !== null) {
                        alert(text(data));
                        $("input#qty").val("");
                    } else {
                        alert("Invalid Item!");
                    }
                }
                );
            }));
        });
    </script>

这是servlet查询.

And this is servlet query.

   while (rs.next()) {

                if (rs.getInt("qty") > qty) {
                    int id = rs.getInt("item_id");
                    Gson gson = new Gson();
                    String json = gson.toJson(id);
                   // System.out.println("one" + json);
                    response.setContentType("application/json");
                    //            response.setCharacterEncoding("UTF-8");
                    response.getWriter().print(json);
                } else {
                    Gson gson = new Gson();
                    String json = gson.toJson("Stock doesn\'t have enough item quantity.");
                  //  System.out.println("two" + json);
                    response.setContentType("application/json");
                    //          response.setCharacterEncoding("UTF-8");
                    response.getWriter().print(json);
                }
            }

从这两个System.out.println()的输出总是正确的.但不发送回jsp.请帮我解决一下这个.

From both System.out.println() s output is always coming correctly. But not sending to jsp back. Please help me with this.

答

您必须做的也是一种最佳实践，它是使用需要传递给gson库的属性来创建DTO类.

what you have to do and also a best practice is to create a DTO class with the properties that you need to pass to gson library.

    public class ResponseDTO implements Serializable{
          private Integer id;
          //more properties ...

          public Integer getId() {
            return id;
          }
          public void setId(Integer id) {
              this.id= id;
          }  

           // other getters & setters
   }

在循环中，将值设置为dto对象，然后将其传递给gson.

and inside your loop, set the values to the dto object, then pass it to gson.

Gson gson = new Gson();
          ResponseDTO dto = null;
          String json = "";
          response.setContentType("application/json");
          ......
          if (rs.getInt("qty") > qty) {
                dto = new ResponseDTO();
                int id = rs.getInt("item_id");
                dto.setId(id); 
                ......

                json = gson.toJson(dto);            
            } else {
               ...... // similar
                json = gson.toJson("{data: 'Some message'}");
            }
        response.getWriter().print(json);

gson将为您提供客户端适当的json结构. 尝试看看！

gson will give you the proper json structure to the client side. try and see !

如何将servlet的json输出发送到jsp?

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