以下代码不会向相应的表中插入一行。 我已经测试了数据库连接并在数据库中运行了查询，这两项都通过了，但是当我通过 .jsp 表单添加输入时，值仍然没有插入。
public class UserDao {
public String registerUser(User user){
String username = user.getUsername();
String email = user.getEmail();
String password = user.getPassword();
Connection con;
con = DBConnection.createConnection();
PreparedStatement preparedStatement;
try{
con.setAutoCommit(false);
String query = ("INSERT INTO user (username, email, password, user_id) VALUES(?, ?, ?, ?)");
preparedStatement = con.prepareStatement(query);
preparedStatement.setString(1, username);
preparedStatement.setString(2, email);
preparedStatement.setString(3, password);
preparedStatement.setString(4,null);
int i = preparedStatement.executeUpdate();
con.commit();
preparedStatement.close();
con.close();
if(i !=0 ){
return "SUCCESS";
}
}catch(SQLException e){
throw new RuntimeException(e);
}
return "Something is wrong!";
}
作为引用，我的 servlet 类和 .jsp 文件也如下所示:
public class UserRegistrationServlet extends HttpServlet {
public UserRegistrationServlet(){}
/**
* Handles the HTTP <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String userName = request.getParameter("username");
String email = request.getParameter("email");
String password = request.getParameter("password");
User user = new User();
user.setUsername(userName);
user.setEmail(email);
user.setPassword(password);
UserDao userDao = new UserDao();
String userRegistered = userDao.registerUser(user);
if(userRegistered.equals("SUCCESS")){
request.getRequestDispatcher("test.jsp").forward(request, response);
}else{
request.setAttribute("error", userRegistered);
request.getRequestDispatcher("/UserRegistration.jsp").forward(request, response);
}
}
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Register</title>
<script>
function validate()
{
var username = document.form.username.value;
var email = document.form.email.value;
var password = document.form.password.value;
var conpassword= document.form.conpassword.value;
if (username==null || username=="")
{
alert("Full Name can't be blank");
return false;
}
else if (email==null || email=="")
{
alert("Email can't be blank");
return false;
}
else if(password.length<6)
{
alert("Password must be at least 6 characters long.");
return false;
}
else if (password!=conpassword)
{
alert("Confirm Password should match with the Password");
return false;
}
}
</script>
</head>
<body>
<center><h2>Java Registration application using MVC and MySQL </h2></center>
<form name="form" action="UserRegistrationServlet" method="post" onsubmit="return validate()">
<table align="center">
<tr>
<td>Username</td>
<td><input type="text" name="username" /></td>
</tr>
<tr>
<td>Email</td>
<td><input type="text" name="email" /></td>
</tr>
<tr>
<td>Password</td>
<td><input type="password" name="password" /></td>
</tr>
<tr>
<td>Confirm Password</td>
<td><input type="password" name="conpassword" /></td>
</tr>
<tr>
<td><%=(request.getAttribute("errMessage") == null) ? ""
: request.getAttribute("errMessage")%></td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="Register"></input><input
type="reset" value="Reset"></input></td>
</tr>
</table>
</form>
</body>
</html>
不确定我的代码哪里出错了，所以任何建议都会很有帮助。谢谢
更新:
[![抛出运行时异常后][2]][2]
最佳答案
您将 user_id 设置为 null 并且数据库提示该列不能为 null。我假设您没有将 null 传递给直接针对数据库测试的语句，因此您设置的是空字符串(或者表是设置默认值或自动生成的值，以防万一它丢失了)。
如果有默认值或自动生成的值，您只需在插入语句中保留 user_id 即可，它应该可以工作。
关于java - JDBC插入查询不更新mysql数据库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/55110664/