Question

在这段代码中，我将MySQL数据库的值放入数据库中表的String array(list[count])和count=number行。当我使用for-loop在javascript的下拉列表中打印这些值时，使用j变量，编译器无法识别j。我无法理解为什么。请帮帮我。

<%@page import="java.sql.DriverManager"%>
<%@page import="com.mysql.jdbc.Driver"%>
<%@page import="java.sql.Connection"%>
<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.ResultSet"%>
<html>
<body>
<br/>
<br/>
<div align="center"><h1>Task Assignment</h1></div>
<form name="taskassignment"><div align="center"><table>
<tr><td><font size="5">Person(s)</font></td><td><select id="person"></select></td></tr>
<tr><td><font size="5">Task(s)</font></td><td><select name="task"></select></td></tr>
<tr><td></td><td><input type="submit" value="Assign" name="assigntask"/></td></tr></div></table></form>
<%
DriverManager.registerDriver(new Driver());
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/BI","root","mayur");
String query = "select name from records";
PreparedStatement stmt = conn.prepareStatement(query);
ResultSet rs = stmt.executeQuery();
int count =0;
while(rs.next())
{
count++;    
}

String[] list = new String[count];
int i=0;
rs.beforeFirst();
while(rs.next())
{

list[i] = rs.getString(1);
out.println(list[i]);
i++;

}

%>

<script>
function myFunction()
{
for(var j=1;j<=<%=list.length%>;j++)
{
    var x = document.getElementById("person");
    var opt =  document.createElement("option");
    opt.text = '<%=list[j]%>';
    opt.value = '<%=list[j]%>'; 
    x.add(opt);

}
}
window.onload = myFunction;
</script>
</body>
</html>

Answer 1

考虑这个jsp scriplet来填充你的选择。我用评论突出了注意事项。一旦你完成了这项工作，请务必阅读JSTL - Scriplets非常古老。

<select id="person">
<%
//no longer needed for 99% of jdbc drivers
DriverManager.registerDriver(new Driver());

//Dont EVER post realusernames/passwords!
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/BI","root","mayur");
String query = "select name from records";
PreparedStatement stmt = conn.prepareStatement(query);
ResultSet rs = stmt.executeQuery();

while(rs.next()) {
   String item = rs.getString(1);
   //now produce html select
%><option value='<%= item %>'><%= item %></option><%
}
rs.close ();
stmt.close ();
conn.close ();
%>
</select>

更多说明：

想到使用连接池。建立连接很昂贵
try-with-resource可以帮助最小化捕获/关闭代码开销
检查jstl

Answer 2

嗨，Mayur我按照我的表格和一点点代码更改了查询。请根据要求进行修改。我在我的本地＆amp;它正在添加所有的字段。它会工作，但正如Jan建议的那样也引用JSTL，因为scriptlet很难维护

    <%@page import="java.sql.DriverManager"%>
    <%@page import="com.mysql.jdbc.Driver"%>
    <%@page import="java.sql.Connection"%>
    <%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.ResultSet"%>
<%@page import="java.util.*"%>
<html>
<body>
<br/>
<br/>
<div align="center"><h1>Task Assignment</h1></div>
<%

String hiddenResult = "";
DriverManager.registerDriver(new Driver());
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/wiprodb","root","1234");
String query = "select state from state_tb";
PreparedStatement stmt = conn.prepareStatement(query);
ResultSet rs = stmt.executeQuery();
int count =0;
while(rs.next())
{

    hiddenResult = hiddenResult+ (rs.getString(1))+",";   
}

hiddenResult = hiddenResult.substring(0, hiddenResult.length()-1);

%>

<form name="taskassignment">

<input type="hidden" id="hiddenDDResult" name="hiddenDDResult" value="<%=hiddenResult%>" />
<div align="center">
<table>
<tr>
    <td><font size="5">Person(s)</font></td>
    <td><select id="person"></select></td>
</tr>
<tr>
    <td><font size="5">Task(s)</font></td>
    <td><select name="task"></select></td>
</tr>
<tr>
    <td></td>
    <td><input type="submit" value="Assign" name="assigntask"/></td>
</tr>

</table>
</div>
</form>

<script>
function myFunction()
{

    var ddResult = document.getElementById("hiddenDDResult").value;
    var ddElement = document.getElementById("person");

    var tempValue = ddResult.split(",");
    //alert('ddResult'+ddResult);
for(var i=0;i<tempValue.length;i++)
{
    var opt =  document.createElement("option");
    opt.text = tempValue[i];
    opt.value = tempValue[i];  
    ddElement.add(opt);

}
}
myFunction();
</script>
</body>
</html>

Answer 3

未经测试，但下面的内容应该可以使用

<%@page import="java.sql.DriverManager"%>
<%@page import="com.mysql.jdbc.Driver"%>
<%@page import="java.sql.Connection"%>
<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.ResultSet"%>
<html>
<body>
<br/>
<br/>
<div align="center"><h1>Task Assignment</h1></div>
<form name="taskassignment"><div align="center"><table>
<tr><td><font size="5">Person(s)</font></td><td>

<select id="person">


<%
DriverManager.registerDriver(new Driver());
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/BI","root","mayur");
String query = "select name from records";
PreparedStatement stmt = conn.prepareStatement(query);
ResultSet rs = stmt.executeQuery();
int count =0;
while(rs.next())
{
count++;    
}

String[] list = new String[count];
int i=0;
rs.beforeFirst();
while(rs.next())
{

list[i] = rs.getString(1);
out.println(list[i]);
%>
<option value='<%=list[i]%>'><%=list[i]%></option>
<% 
i++;
}
%>

</select>

</td></tr>
<tr><td><font size="5">Task(s)</font></td><td><select name="task"></select></td></tr>
<tr><td></td><td><input type="submit" value="Assign" name="assigntask"/></td></tr></div></table></form>
</body>
</html>

局部变量无法解决？

3 个答案: