如何使用servlet在jsp中填充下拉列表？

问题描述

我是jsp和servlets的初学者。我想留在同一页面并填充下拉列表，但我不能这样做。我是用scriplet做的，它发生了但是很久以前就弃用了scriplets。我只是想了解更多关于web.xml中的servlet映射。我猜这个映射有问题。请尽快帮助。



我的尝试：



.jsp

< form> 
< select name =sourcestyle =width：180 px>< / select> 
 
< c：forEach items =$ {slist}var =ls> 
< option> < c：out value =$ {ls}/>< / option> 
 
< / c：forEach> 
< / form> 

在Servlet中

 protected void doGet（HttpServletRequest request，HttpServletResponse response）抛出ServletException，IOException {
 
 try {
 Class.forName（com.mysql.cj.jdbc.Driver）; 
 Connection con = DriverManager.getConnection（
jdbc：mysql：// localhost：3306 / dbname，root，password）; 
语句stmt = con.createStatement（）; 
 ResultSet rs = stmt.executeQuery（select * from City）; 
 while（rs.next（））
 {
 i = rs.getInt（1）; 
 val = rs.getString（2）; 
 ar.add（val）; 
 
} 
 request.setAttribute（slist，ar）; 
 
 
 request.getRequestDispatcher（/ WebContent / Home.jsp）。forward（request，response）; 
 //rd.forward(req,res）; 
 //System.out.println(rs.getInt(1)++ rs.getString（2）+）; 
 con.close（）; 
} catch（例外e）{System.out.println（e）;} 
最后
 {
 
} 
 
} 

解决方案

I am a beginner in jsp and servlets. I want to stay in the same page and populate the dropdownlist but iam not able to so. I did it using scriplets and it happened but scriplets are deprecated long back. I just want to know more about servlet mapping in web.xml. I guess something is wrong with the mapping. Please somebody help asap.

What I have tried:

Home.jsp

<form>
<select name="source" style="width:180 px"></select>

    <c:forEach items="${slist}" var="ls">
     <option> <c:out value="${ls}"/></option>

    </c:forEach>
</form>

In Servlet

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

	try{
			Class.forName("com.mysql.cj.jdbc.Driver");
			Connection con=DriverManager.getConnection(
		"jdbc:mysql://localhost:3306/dbname","root","password");
			Statement stmt=con.createStatement();
			ResultSet rs=stmt.executeQuery("select * from City");
			while(rs.next())
			{
			     i=rs.getInt(1);
			     val=rs.getString(2);
			     ar.add(val);

			}
			 request.setAttribute("slist",ar);


                 request.getRequestDispatcher("/WebContent/Home.jsp").forward(request, response);
		     //rd.forward(req,res);
		     //System.out.println(rs.getInt(1)+"  "+rs.getString(2)+"  ");
			con.close();
			}catch(Exception e){ System.out.println(e);}
		finally
		{

		}

	}

解决方案

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