JDBC示例程序

 import java.io.IOException;
 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.Properties;

 import org.apache.commons.dbcp.BasicDataSource;

 public class DBUtils {
     private static BasicDataSource dateSource;
     static {
         //创建属性对象
                 Properties prop = new Properties();
                 //得到文件的输入流
                 InputStream ips = DBUtils2.class.getClassLoader().getResourceAsStream("jdbc.properties");
                 //把文件加载到属性对象中
                 try {
                     prop.load(ips);
                     //读取数据
                     String driver = prop.getProperty("driver");
                     String url = prop.getProperty("url");
                     String username = prop.getProperty("username");
                     String password = prop.getProperty("password");
                     //创建数据源对象
                     dateSource = new BasicDataSource();
                     //设置数据库链接信息
                     dateSource.setDriverClassName(driver);
                     dateSource.setUrl(url);
                     dateSource.setUsername(username);
                     dateSource.setPassword(password);
                     //设置连接池参数
                     dateSource.setInitialSize(3);//初始连接数量
                     dateSource.setMaxActive(5);//最大连接数量

                 } catch (IOException e) {
                     e.printStackTrace();
                 }

     }
     //1、获取链接
     public static Connection getConn() throws Exception {

                 //获取连接池中的连接
                 Connection conn = dateSource.getConnection();
         return conn;
     }
     //2、关闭资源
     public static void close(ResultSet rs,Statement stat,Connection conn) {
         try {
             if (rs!=null) {
                 rs.close();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
         try {
             if (stat!=null) {
                 stat.close();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
         //关闭连接
         try {
             if (conn!=null) {
                 conn.close();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }
 }

DAO

 /**
      * 依据用户名查询对应的用户信息。 如果找不到，返回null。
      *
      * @throws SQLException
      */
     public User find(String uname) throws SQLException {
         User user = null;

         Connection conn = null;
         PreparedStatement ps = null;
         ResultSet rs = null;

         try {
             conn = DBUtils.getconn();
             String sql = "SELECT * FROM t_user " + "WHERE username=?";
             ps = conn.prepareStatement(sql);
             ps.setString(1, uname);
             rs = ps.executeQuery();

             if (rs.next()) {
                 int id = rs.getInt("id");
                 String pwd = rs.getString("password");
                 String email = rs.getString("email");

                 user = new User();
                 user.setId(id);
                 user.setUname(uname);
                 user.setPwd(pwd);
                 user.setEmail(email);

             }

         } catch (SQLException e) {
             e.printStackTrace();
             throw e;
         } finally {
             DBUtils.close(rs, ps, conn);
         }

         return user;
     }
     /**
      *     删除指定信息
      * @param id
      * @throws SQLException
      */
     public void delete(int id) throws SQLException {
         Connection conn = null;
         PreparedStatement ps = null;

         try {
             conn = DBUtils.getconn();
             String sql = "DELETE FROM t_user " + "WHERE id = ?";
             ps = conn.prepareStatement(sql);
             ps.setInt(1, id);
             ps.executeUpdate();

         } catch (SQLException e) {
             e.printStackTrace();
             throw e;
         } finally {
             DBUtils.close(null, ps, conn);
         }
     }

     /**
      * 将用户信息插入到t_user表。
      *
      * @throws SQLException
      *
      */
     public void save(User user) throws SQLException {
         Connection conn = null;
         PreparedStatement ps = null;

         try {
             conn = DBUtils.getconn();
             String sql = "INSERT INTO t_user " + "VALUES(null,?,?,?)";
             ps = conn.prepareStatement(sql);
             ps.setString(1, user.getUname());
             ps.setString(2, user.getPwd());
             ps.setString(3, user.getEmail());
             ps.executeUpdate();

         } catch (SQLException e) {
             e.printStackTrace();
             throw e;
         } finally {
             DBUtils.close(null, ps, conn);
         }
     }

     /**
      * 从t_user表中查询出所有用户的信息。 注： 一条记录对应一个User对象(即将记录中的数据 存放到User对象里面)。
      *
      * @throws SQLException
      */
     public List<User> findAll() throws SQLException {

         List<User> users = new ArrayList<User>();

         Connection conn = null;
         PreparedStatement ps = null;
         ResultSet rs = null;

         try {
             conn = DBUtils.getconn();
             String sql = "SELECT * FROM t_user";
             ps = conn.prepareStatement(sql);
             rs = ps.executeQuery();

             while (rs.next()) {

                 int id = rs.getInt("id");
                 String uname = rs.getString("username");
                 String pwd = rs.getString("password");
                 String email = rs.getString("email");

                 User user = new User();
                 user.setId(id);
                 user.setUname(uname);
                 user.setPwd(pwd);
                 user.setEmail(email);

                 users.add(user);

             }

         } catch (SQLException e) {
             e.printStackTrace();
             throw e;
         } finally {
             DBUtils.close(rs, ps, conn);
         }

         return users;

     }

Java中访问数据库的步骤

 //注册驱动
 Class.forName("com.mysql.jdbc.Driver");
                 //建立连接
         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "");
         System.out.println("创建完毕");
                 //创建Statement
         Statement stat = conn.createStatement();
         String sql = "delete from jdbc01 where id=1";
                 //执行sql语句(若SQL语句为查询语句需要处理结果集)
         stat.executeUpdate(sql);
         System.out.println("删除完毕");
                 //关闭连接
         stat.close();
         conn.close();

数据库的基本连接

 public static void main(String[] args) throws Exception {
         //创建数据源对象
         BasicDataSource dateSource = new BasicDataSource();
         //设置数据库连接信息
         dateSource.setDriverClassName("com.mysql.jdbc.Driver");
         dateSource.setUrl("jdbc:mysql://localhost:3306/db3");
         dateSource.setUsername("root");
         dateSource.setPassword("root");
         //设置连接池参数
         dateSource.setInitialSize(3);//初始连接数量
         dateSource.setMaxActive(5);//最大连接数量
         //获取连接池中的连接
         Connection conn = dateSource.getConnection();
         System.out.println(conn);
     }