Ajax dropdown list add data

This time I bring you AjaxDrop-down listAdd data, what are the precautions for adding data to Ajax drop-down list, the following is a practical case, let's take a look.

1. In the front-end jsp, create a new drop-down control

2. In the js part, create a function method, use ajax, point to the servlet part of 'getAllTypes.action', and obtain the incoming drop-down The data in the list is dynamically filled

 function loadType(){ 
   $.get( 
       'getAllTypes.action', 
     function(data){ 
      var $sel = $("#seldvd"); 
      // console.log(data); 
      for(var i = 0;i        $item = $(""); //添加option 
        $item.val(data[i].id); //添加option的value ，数据库中用id和type保存的数据 
        $item.html(data[i].type); //添加option数据 
        $sel.append($item); //将option添加进select 
        } 
       },'json' 
      ); 
 }

3. Create a new servlet page to return data to Ajax

public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    request.setCharacterEncoding("utf-8"); 
    ArrayList typeList = new ArrayList(); 
    typeDao td = new typeDao(); 
    typeList = td.getAllTypes(); 
    JSONArray arr = new JSONArray(typeList);//这里导入需要转json数据包 
    String jsString = arr.toString(); 
    //响应到客户端     
    request.setCharacterEncoding("utf-8"); 
    response.setContentType("text/plain;charset=utf-8"); 
    response.getWriter().print(jsString); //返回下拉列表需要的json格式数据 
  }

4. So the question is, where is the source of this data? Of course in the database (MySQL). So first we need to write a method to read the data in the database

typeInfo.java

import java.io.Serializable; 
public class typeInfo implements Serializable { 
  private int id; 
  private String type; 
  public int getId() { 
    return id; 
  } 
  public void setId(int id) { 
    this.id = id; 
  } 
  public String getType() { 
    return type; 
  } 
  public void setType(String type) { 
    this.type = type; 
  } 
  public typeInfo(){ 
  } 
  public typeInfo(int id, String type) { 
    this.id = id; 
    this.type = type; 
  } 
}

TypeDao.java (need to import the JDBC package)

import java.sql.Connection; 
import java.sql.PreparedStatement; 
import java.sql.ResultSet; 
import java.util.ArrayList; 
import model.typeInfo; 
public class typeDao extends baseDao { 
  public ArrayList getAllTypes(){ 
    ArrayList typeList = new ArrayList(); 
    Connection con = null; 
    PreparedStatement psm = null; 
    ResultSet rs = null; 
    try { 
      con = super.getConnection(); 
      psm = con.prepareStatement("select * from types"); 
      rs = psm.executeQuery(); 
      while(rs.next()){ 
        typeInfo types = new typeInfo(); 
        types.setId(rs.getInt(1)); 
        types.setType(rs.getString(2)); 
        typeList.add(types); 
      } 
    } catch (Exception e) { 
      System.out.println("显示所有类型报错："+e.getMessage()); 
    }finally{ 
      super.closeAll(rs, psm, con); 
    } 
    return typeList; 
  //  
  } 
}

I believe you have mastered the method after reading the case in this article, please come for more exciting information Pay attention to other related articles on php Chinese website!

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