我正在尝试将 servlet
与 mysql
数据库连接...但是在 servlet 代码中...
声明:
Class.forName(driver)
在工具提示上显示带有红色下划线的错误-
Syntax error on token-"driver",VariableDeclaratorId expected after this token.
我只是不明白为什么会这样..
这是servlet代码:
package Servlets;
import java.io.IOException;
import java.sql.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
public LoginServlet()
{
super();
}
Connection con = null;
String url = "jdbc:mysql://localhost:3306/";
String db = "abc";
String driver = "com.mysql.jdbc.Driver";
Class.forName(driver);
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
String username= request.getParameter("username");
String password= request.getParameter("password");
con = DriverManager.getConnection("url+db","root","root");
Statement st = con.createStatement();
int val = st.executeUpdate("INSERT login values("+username+","+password+")");
System.out.println("1 row affected");
response.sendRedirect("login.jsp");
}
}
最佳答案
我会把
Class.forName("com.mysql.jdbc.Driver").newInstance();
线就在上面
con = DriverManager.getConnection("url+db","root","root");
请记住,servlet 需要是多线程的,这样您的
Connection con = null;
当两个用户尝试同时登录时可能会给您带来问题。
另外,你需要正确关闭连接
try {
if(con != null)
con.close();
} catch(SQLException e) {}
最后,您需要处理数据库访问可能导致的任何异常,因此将其包装在 try catch block 中。
package Servlets;
import java.io.IOException;
import java.sql.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
public LoginServlet()
{
super();
}
String url = "jdbc:mysql://localhost:3306/";
String db = "abc";
String driver = "com.mysql.jdbc.Driver";
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
try{
Connection con = null;
String username= request.getParameter("username");
String password= request.getParameter("password");
Class.forName(driver).newInstance();
con = DriverManager.getConnection("url+db","root","root");
Statement st = con.createStatement();
int val = st.executeUpdate("INSERT login values("+username+","+password+")");
System.out.println("1 row affected");
response.sendRedirect("login.jsp");
}catch(SQLException e){}
finally{
try {
if(con != null)
con.close();con=null;
} catch(SQLException e) {}
}
}
}
或者类似的东西。
最后要注意的是,使用“连接池”要好得多。
关于mysql - Servlet-数据库连接问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9191567/