java无法使用servlet和jsp更新表中的特定记录
嘿，伙计们，我已经为用户创建了一个jsp页面，在这里他们可以更新他们现有的详细信息，并在提交时更新数据库中的记录
一,&燃气轮机帐户详细信息。java
//Java Servlet program responsible for obtaining the user data and updating into database
package roseindia.net;
import java.io.*;
import java.sql.*;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class Accountdetails
*/
@WebServlet("/Accountdetails")
public class Accountdetails extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Accountdetails() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("Servlet is in the doGet method of account details");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("Servlet is in the doPost method of account details");
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
pw.println("<html>");
pw.println("<body>");
pw.println("<h1>Hello Servlet Post</h1>");
pw.println("</body>");
pw.println("</html>");
Connection conn=null;
String url="jdbc:mysql://localhost:3306/";
String dbName="userlogindb";
String driver="com.mysql.jdbc.Driver";
try{
String Fname = request.getParameter("fname");
String Mname = request.getParameter("mname");
String Lname = request.getParameter("lname");
String Uname = request.getParameter("username");
String Emailid = request.getParameter("emailid");
String Mobno = request.getParameter("mobno");
String Address = request.getParameter("address");
String Password1 = request.getParameter("password1");
String Password2 = request.getParameter("password2");
String ID = request.getParameter("id");
Class.forName(driver);
conn = DriverManager.getConnection(url+dbName,"root", "root");
String update="update registerutable set fname='"+Fname+"', mname='"+Mname+"', lname='"+Lname+"', username='"+Uname+"', emailid='"+Emailid+"', mobno='"+Mobno+"', address='"+Address+"', password1='"+Password1+"', password2='"+Password2+"' where id='"+ID+"' ";
System.out.println("The sql is " +update);
PreparedStatement pst = (PreparedStatement) conn.prepareStatement(update);
pst.setString(1,Fname);
pst.setString(2,Mname);
pst.setString(3,Lname);
pst.setString(4,Uname);
pst.setString(5,Emailid);
pst.setString(6,Mobno);
pst.setString(7,Address);
pst.setString(8,Password1);
pst.setString(9,Password2);
pst.setString(11,ID);
int i = pst.executeUpdate();
String msg=" ";
if(i!=0){
msg="User Updated";
pw.print(i);
pw.print("<font size='6' color=blue>" + msg + "</font>");
pw.print(" '"+Fname+"'");
}
else{
msg="failed to update the data";
pw.print("<font size='6' color=blue>" + msg + "</font>");
}
pw.close();
pst.close();
conn.close();
}
catch (Exception e){
e.printStackTrace();
}
}
}
二,&燃气轮机成功。jsp
//JSP page which shows existing value and new value to be entered by user.
<form name="myaccountform" action="Accountdetails" method="post">
<table border="1">
<tr>
<td>First name:</td>
<%Object value11 = request.getAttribute("fname");%>
<td><%=value11%></td>
</tr>
<tr>
<td>Enter the new first name:</td>
<td><input type="text" name="fname" value=""></td>
</tr>
<tr>
<td>Middle name:</td>
<%Object value12 = request.getAttribute("mname");%>
<td><%=value12%></td>
</tr>
<tr>
<td>Enter the new middle name:</td>
<td><input type="text" name="mname" value=""></td>
</tr>
<tr>
<td>Last name:</td>
<%Object value13 = request.getAttribute("lname");%>
<td><%=value13%></td>
</tr>
<tr>
<td>Enter the new last name:</td>
<td><input type="text" name="lname" value=""></td>
</tr>
<tr>
<td>Username:</td>
<%Object value14 = request.getAttribute("uname");%>
<td><%=value14%></td>
</tr>
<tr>
<td>Enter new username:</td>
<td><input type="text" name="username" value=""></td>
</tr>
<tr>
<td>Email id:</td>
<%Object value15 = request.getAttribute("emailid");%>
<td><%=value15%></td>
</tr>
<tr>
<td>Enter new email id:</td>
<td><input type="text" name="emailid" value=""></td>
</tr>
<tr>
<td>Mobile number:</td>
<%Object value16 = request.getAttribute("mobno");%>
<td><%=value16%></td>
</tr>
<tr>
<td>Enter new mobile number:</td>
<td><input type="text" name="mobno" value=""></td>
</tr>
<tr>
<td>Address:</td>
<%Object value17 = request.getAttribute("address");%>
<td><%=value17%></td>
</tr>
<tr>
<td>Enter new address:</td>
<td><textarea rows="5" cols="15" name="address"></textarea></td>
</tr>
<tr>
<td>Old password:</td>
<%Object value18 = request.getAttribute("password1");%>
<td><%=value18%></td>
</tr>
<tr>
<td>Enter the new password:</td>
<td><input type="password" name="password1" value=""></td>
</tr>
<tr>
<td>Reenter the new password:</td>
<td><input type="password" name="password2" value=""></td>
</tr>
</table>
<input type="submit">
</form>
三,&燃气轮机web。xml
//mapping between servlet and jsp
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web- app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>LoginExample</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<description>Login Servlet</description>
<display-name>Login</display-name>
<servlet-name>Login</servlet-name>
<servlet-class>roseindia.net.Login</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Login</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
<servlet>
<description>Servlet Example</description>
<display-name>ServletExample</display-name>
<servlet-name>ServletExample</servlet-name>
<servlet-class>servletexample.com.ServletExample</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ServletExample</servlet-name>
<url-pattern>/register</url-pattern>
</servlet-mapping>
<servlet>
<description>Account Details</description>
<display-name>Accountdetails</display-name>
<servlet-name>Accountdetails</servlet-name>
<servlet-class>roseindia.net.Accountdetails</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Accountdetails</servlet-name>
<url-pattern>/Accountdetails</url-pattern>
</servlet-mapping>
</web-app>
这里的问题是，当填写所有字段并单击“提交”时，它无法更新
它进入else部分，显示更新数据失败
当我sysout时，它显示sql是
update registerutable set
fname='admin11', mname='admin11', lname='admin11', username='admin11',
emailid='admin', mobno='1111', address='admin', password1='admin',
password2='admin'
where id='null'
我也试过了
String ID = request.getParameter("id");
到
int ID = Integer.parseInt(request.getParameter("id"));
但仍然无法更新它
请帮我改正，因为我不知道我现在哪里出了问题
# 1 楼答案
因为列ID的mysql Database中的数据类型是
int所以改变
pst.setString(11,ID);到pst.setInt(11,ID);但是ID是一个字符串，所以需要使用
Integer.parseInt();将其转换为int# 2 楼答案
您的代码中有几个错误：
您的servlet似乎没有收到查询参数
id此语句必须导致variabl
ID持有null在
JSP中，您没有为id设置表单变量，因此AccountDetailsservlet没有接收到它因此，相同的
null被传递给update查询语句，该语句不更新数据库表中的任何记录条件
where id='null'与任何记录都不匹配，因此未成功准备语句的sql字符串格式错误。您应该有
PreparedStatement的占位符来绑定值更改：
致：
# 3 楼答案
您可以尝试通过将变量名替换为问号来修改对引用更新字符串的赋值，因为您使用的是准备好的语句来执行表更新
# 4 楼答案
您的代码：
你犯了一些错误：
您应该看下面这一行：
此字段名，如：（错误页）
现在你明白你的错误了，你应该改变它并编译它