如何使用JDBC连接到数据库？假设数据库名称为TESTDB，它有表employee，并且表中有2条记录。

解决方法

下面的示例使用getConnection()，createStatement()和executeQuery()方法来连接到数据库和执行查询。

import java.sql.*;

public class jdbcConn {
   public static void main(String[] args) {
      try {
         Class.forName("org.apache.derby.jdbc.ClientDriver");
      }
      catch(ClassNotFoundException e) {
         System.out.println("Class not found "+ e);
      }
      System.out.println("JDBC Class found");
      int no_of_rows = 0;
      try {
         Connection con = DriverManager.getConnection
         ("jdbc:derby://localhost:1527/testDb","username",
         "password");  
         Statement stmt = con.createStatement();
         ResultSet rs = stmt.executeQuery
         ("SELECT * FROM employee");
         while (rs.next()) {
            no_of_rows++;
         }
         System.out.println("There are "+ no_of_rows 
         + " record in the table");
      }
      catch(SQLException e){
         System.out.println("SQL exception occured" + e);
      }
   }
}

结果

上面的代码示例将产生以下结果。该结果可能会不同。如果JDBC驱动程序未正确安装，将得到ClassNotFound异常。

JDBC Class found
There are 2 record in the table