java之JDBC

一.什么是JDBC

Java 数据库连接，（Java Database Connectivity，简称JDBC）是Java语言中用来规范客户端程序如何来访问数据库的应用程序接口，提供了诸如查询和更新数据库中数据的方法。JDBC也是Sun Microsystems的商标。JDBC是面向关系型数据库的。

首先要获取连接：

 private static Connection getConn() {

     String driver = "com.mysql.jdbc.Driver";

     String url = "jdbc:mysql://localhost:3306/samp_db";

     String username = "root";

     String password = "";

     Connection conn = null;

     try {

         Class.forName(driver); //classLoader,加载对应驱动

         conn = (Connection) DriverManager.getConnection(url, username, password);

     } catch (ClassNotFoundException e) {

         e.printStackTrace();

     } catch (SQLException e) {

         e.printStackTrace();

     }

     return conn;

 }

进行添加的代码例子：

 private static int insert(Student student) {

     Connection conn = getConn();

     int i = 0;

     String sql = "insert into students (Name,Sex,Age) values(?,?,?)";

     PreparedStatement pstmt;

     try {

         pstmt = (PreparedStatement) conn.prepareStatement(sql);

         pstmt.setString(1, student.getName());

         pstmt.setString(2, student.getSex());

         pstmt.setString(3, student.getAge());

         i = pstmt.executeUpdate();

         pstmt.close();

         conn.close();

     } catch (SQLException e) {

         e.printStackTrace();

     }

     return i;

 }

进行更新的代码例子：

 private static int update(Student student) {

     Connection conn = getConn();

     int i = 0;

     String sql = "update students set Age='" + student.getAge() + "' where Name='" + student.getName() + "'";

     PreparedStatement pstmt;

     try {

         pstmt = (PreparedStatement) conn.prepareStatement(sql);

         i = pstmt.executeUpdate();

         System.out.println("resutl: " + i);

         pstmt.close();

         conn.close();

     } catch (SQLException e) {

         e.printStackTrace();

     }

     return i;

 }

进行查询的代码例子：

 private static Integer getAll() {

     Connection conn = getConn();

     String sql = "select * from students";

     PreparedStatement pstmt;

     try {

         pstmt = (PreparedStatement)conn.prepareStatement(sql);

         ResultSet rs = pstmt.executeQuery();

         int col = rs.getMetaData().getColumnCount();

         System.out.println("============================");

         while (rs.next()) {

             for (int i = 1; i <= col; i++) {

                 System.out.print(rs.getString(i) + "\t");

                 if ((i == 2) && (rs.getString(i).length() < 8)) {

                     System.out.print("\t");

                 }

              }

             System.out.println("");

         }

             System.out.println("============================");

     } catch (SQLException e) {

         e.printStackTrace();

     }

     return null;

 }

进行删除的代码例子：

 private static int delete(String name) {

     Connection conn = getConn();

     int i = 0;

     String sql = "delete from students where Name='" + name + "'";

     PreparedStatement pstmt;

     try {

         pstmt = (PreparedStatement) conn.prepareStatement(sql);

         i = pstmt.executeUpdate();

         System.out.println("resutl: " + i);

         pstmt.close();

         conn.close();

     } catch (SQLException e) {

         e.printStackTrace();

     }

     return i;

 }

jdbc在执行增删改查的时候的通用流程：

(1)创建Connection对象、SQL查询命令字符串；

　　(2)对Connection对象传入SQL查询命令，获得PreparedStatement对象；

　　(3)对PreparedStatement对象执行executeUpdate()或executeQurey()获得结果；

　　(4)先后关闭PreparedStatement对象和Connection对象。

　　可见，使用JDBC时，最常打交道的是Connection、PreparedStatement这两个类，以及select中的ResultSet类。

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java之JDBC

一.什么是JDBC

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