使用JSP和MySQL执行查询时会自动插入空值 [英] Null values automatically inserted when executing a query using JSP and MySQL
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问题描述
当我执行下面的代码时，在每次插入之前，自动用空值填充一行，然后插入实际值.
When I execute the code below, before every insert, automatically a row is getting filled with Null values and then the actual values are being inserted.
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link rel="stylesheet" href="style.css" type="text/css">
<title>Connecting to a Data base</title>
</head>
<body>
<%
String connectionURL="jdbc:mysql://localhost:3306/jsp_test";
Connection connection = null;
Class.forName("com.mysql.jdbc.Driver").newInstance();
connection = DriverManager.getConnection(connectionURL, "root", "exeterblr");
if(!connection.isClosed()) {
out.println("Successfully connected to " + "MySQL server using TCP/IP...");
}
else
{
out.println("Cannot connect to DB");
}
String name=request.getParameter("name");
String email=request.getParameter("email");
String phone=request.getParameter("phone");
PreparedStatement pstatement=null;
int updateTable=0;
String queryString = "INSERT INTO sample_info(name,email,phone) VALUES (?, ?, ?)";
pstatement=connection.prepareStatement(queryString);
pstatement.setString(1, name);
pstatement.setString(2, email);
pstatement.setString(3, phone);
updateTable=pstatement.executeUpdate();
%>
<form method="post" action="index.jsp">
<table>
<tr>
<td>Name</td><td><input type="text" name="name"></td>
</tr>
<tr>
<td>Email</td><td><input type="text" name="email"></td>
</tr>
<tr>
<td>Phone</td><td> <input type="text" name="phone"></td>
</tr>
</table>
<input type="submit" value="Submit">
</form>
</body>
当我插入一个值时，数据库包含以下内容:
When I insert a value, the database contains the following:
Name Email Phone <br />
NULL NULL NULL <br />
ActualValue ActualValue Actual Value
推荐答案
您每次访问网页时都会插入(NULL，NULL，NULL)，而不仅是在提交时.
You insert (NULL,NULL,NULL) each time you visit your webpage and not only on submit.
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