UC知道请问大家,为什么我用tomcat 连接mysql的时候什么异常都没有,但是返回的connection就偏偏是null?
来源：百度知道 编辑：UC知道 时间：2024/05/27 11:37:14
import java.sql.*;
public class DBConnection {
private static Connection con;
public static Connection getMySQLConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost/ray", "root", "root");
}
catch(ClassNotFoundException e) {
System.out.println("Sorry, you get a ClassNotFoundException");
}
catch(SQLException e) {
System.out.println("Sorry, you get a SQLException");
}
if (con == null) {
System.out.println("con is null");
}
return con;
}
}
程序没有抛出任何异常,可就是输出con is null 我实在不知是哪里出毛病了.
public class DBConnection {
private static Connection con;
public static Connection getMySQLConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost/ray", "root", "root");
}
catch(ClassNotFoundException e) {
System.out.println("Sorry, you get a ClassNotFoundException");
}
catch(SQLException e) {
System.out.println("Sorry, you get a SQLException");
}
if (con == null) {
System.out.println("con is null");
}
return con;
}
}
程序没有抛出任何异常,可就是输出con is null 我实在不知是哪里出毛病了.
private static Connection con; 这里定义了一个con
public static Connection getMySQLConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
这里又定义了一个con,它在try的范围内有效，出了try就没效了。
Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost/ray", "root", "root");
localhost:3306/ray
没有端口号
private static Connection con;
Connection con = 。。。
重新声明了。
里面的 con = ..