表单中有一个文本框,比如代表学号,我输入学号,然后点添加,如果数据库没有这个学号,则添加成功,如果有则提示不能添加。<form method="post" action="1.jsp">
<label>学生学号</label>
<input name="id" id="id" type="text" maxlength="15" />
<input type="submit" value="插入">
</form>
该怎么办呢》?
<label>学生学号</label>
<input name="id" id="id" type="text" maxlength="15" />
<input type="submit" value="插入">
</form>
该怎么办呢》?
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select * from student where stuid = id;如果有就提示不能添加.
若存在,则:request.setAttribute("msg","已经存在");
然后使用转发到页面:request.getRequestDispatch("xxx.jsp").forword(request,response);
页面使用:
${msg }//EL表达式方式得到提示
或者直接使用代码实现
<%
String msg = getAttribute("msg");
%><%=msg%>
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.zshome_admin.hbm.News;
import com.zshome_admin.hbm.NewsDAO;
import com.zshome_admin.hbm.NewsTypeDAO;
import com.zshome_admin.hbm.PersonenlistDAO;public class CheckNtype extends HttpServlet { /**
* Constructor of the object.
*/
public CheckNtype() {
super();
} /**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("text/html");
PrintWriter out = response.getWriter();
response.setCharacterEncoding("utf-8");
String uname = request.getParameter("uname");
String title=request.getParameter("title");
String position=request.getParameter("position");
if(uname!=null){
NewsTypeDAO dao=new NewsTypeDAO();
boolean flg=dao.findSelByTitle(uname);
if(flg)
{
out.println(1);
}else
out.println(0);
}else if(title!=null)
{
NewsDAO ndao=new NewsDAO();
boolean flg=ndao.IsExceTitle(title);
if(flg)
{
out.print(1);
}else
out.print(0);
}else if(position!=null)
{
PersonenlistDAO perdao=new PersonenlistDAO();
boolean flg=perdao.IsExcePosition(position);
if(flg)
{
out.print(1);
}else
out.print(0);
}
out.flush();
out.close();
} /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
} /**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}}首先页面文本框, <tr>
<td align="center" bgcolor="#F6F6F6">新闻标题:</td>
<td height="25" colspan="2" align="left" bgcolor="#F6F6F6" style="width: 367px">
<input type="text" name="title" id="title" onblur="startRequestUsingPOST();" type="text"/>
<label id="message" style="color: red">该标题已存在</label>
<label id="lbltitle" style="color: red">标题不能为空</label> </td>
<td bgcolor="#F6F6F6"> 不能为空</td>
</tr>
然后JS..
function startRequestUsingPOST() {
if(checktitle()==false)
{
return;
}
var title = document.getElementById("title").value;
createXMLHttpRequest();
xmlHttp.open("POST","CheckNtype",true);
xmlHttp.onreadystatechange = processResponse;
xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttp.send("title=" + title);
}
function processResponse() {
if(xmlHttp.readyState == 4) {
if(xmlHttp.status == 200) {
var result = xmlHttp.responseText;
if(result==1){
document.getElementById("message").style.display="inline";
document.getElementById("btnadd").disabled="disabled";
}else
{
document.getElementById("message").style.display="none";
document.getElementById("btnadd").disabled="";
}
}
}
}
function checktitle()
{
var title=document.getElementById("title").value;
if(title=="")
{
document.getElementById("lbltitle").style.display="inline";
return false;
}else
{
document.getElementById("lbltitle").style.display="none";
return true;
}
}然后WEB.XML加上一段配置.
<servlet>
<servlet-name>CheckNtype</servlet-name>
<servlet-class>com.zshome_admin.struts.action.news.CheckNtype</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckNtype</servlet-name>
<url-pattern>/CheckNtype</url-pattern>
</servlet-mapping>自己在理清思路,慢慢改..我现在做的项目就是用这种. 不过还有更简单的.就不说了..