JDBC

The JDBC API is a Java API that can access any kind of tabular data, especially data stored in a Relational Database.

JDBC helps you to write Java applications that manage these three programming activities:

• Connect to a data source, like a database
• Send queries and update statements to the database。
• Retrieve and process the results received from the database in answer to your query

package jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class jdbc_exp {

    public static void main(String[] args) {
        Connection con = null;// 创建一个数据库连接
        PreparedStatement pre = null;// 创建预编译语句对象，一般都是用这个而不用Statement
        ResultSet result = null;// 创建一个结果集对象
        try
        {
            Class.forName("oracle.jdbc.driver.OracleDriver");// 加载Oracle驱动程序
            System.out.println("开始尝试连接数据库！");
            String url = "jdbc:oracle:" + "thin:@10.224.188.188:1521:tonytest";// 127.0.0.1是本机地址，XE是精简版Oracle的默认数据库名
            String user = "hr";// 用户名,系统默认的账户名
            String password = "CCM%lab123";// 你安装时选设置的密码
            con = DriverManager.getConnection(url, user, password);// 获取连接
            System.out.println("连接成功！");
            String sql = "select * from dept order by 1";// 预编译语句，“？”代表参数
            pre = con.prepareStatement(sql);// 实例化预编译语句
            result = pre.executeQuery();// 执行查询，注意括号中不需要再加参数
            while (result.next())
                // 当结果集不为空时
                System.out.println("deptno: " + result.getInt("deptno") + " dname: "
                        + result.getString("dname") + " loc: " + result.getString("loc")
                        + " create_date: " + result.getString("create_date"));
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        finally
        {
            try
            {
                // 逐一将上面的几个对象关闭，因为不关闭的话会影响性能、并且占用资源
                // 注意关闭的顺序，最后使用的最先关闭
                if (result != null)
                    result.close();
                if (pre != null)
                    pre.close();
                if (con != null)
                    con.close();
                System.out.println("数据库连接已关闭！");
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
        }

    }

}