Question

我在Java代码下运行时遇到问题。我找不到DB.java班。

ResultSet rs = DB.getConnection().createStatement().executeQuery("select * from products");
while(rs.next()){
    System.out.print(rs.getString("pid"));
    System.out.print(rs.getString("name"));
    System.out.print(rs.getString("price"));
    System.out.print(rs.getString("ava_qty"));
}

我正在使用Glassfish服务器。有人可以帮我写DB.java班吗？

Answer 1

getConnection（）方法是DriverManager类的一部分。正确初始化您的drivermanager，如本文所述：

https://www.tutorialspoint.com/javaexamples/jdbc_dbconnection.htm

未来参考的示例代码：

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);
      }
   }
}

从数据库中读取表

1 个答案: