package myclass;import java.sql.*;public class Jdbc{
public Connection getConnection()
{
String driver="com.mysql.jdbc.Driver";
String url="jdbc:mysql://localhost:3306/stu";
Connection con=null;
Statement st;
ResultSet rs;
try {
Class.forName(driver);
con=DriverManager.getConnection(url,"root","welcome");
}
catch(ClassNotFoundException ex){
System.out.println("DriverError");
ex.printStackTrace();
}
catch(SQLException ex){
System.out.println("Connection error");
ex.printStackTrace();
} return con ; }
}
package myclass;import java.sql.*;public class Jdbctest{
Jdbc con=new Jdbc();
void dispaly(){
try{
Connection cn = con.getConnection();
String sql="Select * from studo";
Statement s = cn.createStatement();
ResultSet rs = s.executeQuery(sql);
while(rs.next()){
System.out.print(rs.getString(1));
System.out.print(rs.getString(2));
}
}
catch(SQLException ce){
System.out.print(ce);
System.out.println("NULL");
}
}
public static void main(String [] args){
Jdbctest jt = new Jdbctest();
jt.dispaly();
}
}
ClassNotFoundException
用H做的时候非常简单的就出来了 现在手写怎么总是找不这找不到那啊。唉
public Connection getConnection()
{
String driver="com.mysql.jdbc.Driver";
String url="jdbc:mysql://localhost:3306/stu";
Connection con=null;
Statement st;
ResultSet rs;
try {
Class.forName(driver);
con=DriverManager.getConnection(url,"root","welcome");
}
catch(ClassNotFoundException ex){
System.out.println("DriverError");
ex.printStackTrace();
}
catch(SQLException ex){
System.out.println("Connection error");
ex.printStackTrace();
} return con ; }
}
package myclass;import java.sql.*;public class Jdbctest{
Jdbc con=new Jdbc();
void dispaly(){
try{
Connection cn = con.getConnection();
String sql="Select * from studo";
Statement s = cn.createStatement();
ResultSet rs = s.executeQuery(sql);
while(rs.next()){
System.out.print(rs.getString(1));
System.out.print(rs.getString(2));
}
}
catch(SQLException ce){
System.out.print(ce);
System.out.println("NULL");
}
}
public static void main(String [] args){
Jdbctest jt = new Jdbctest();
jt.dispaly();
}
}
ClassNotFoundException
用H做的时候非常简单的就出来了 现在手写怎么总是找不这找不到那啊。唉
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at myclass.Jdbc.getConnection(Jdbc.java:13)
at myclass.Jdbctest.dispaly(Jdbctest.java:8)
at myclass.Jdbctest.main(Jdbctest.java:25)
Exception in thread "main" java.lang.NullPointerException
at myclass.Jdbctest.dispaly(Jdbctest.java:10)
at myclass.Jdbctest.main(Jdbctest.java:25)
C:\Program Files\Java\jdk1.X.0\jre\lib\ext