JDBC之CRUD

JDBC定义

　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。它JDBC是面向关系型数据库的。

准备工作

创建mysql数据库表信息（student表）导入相应的jar 编写javabean类

导入jar包：

import com.mysql.jdbc.Connection; import com.mysql.jdbc.PreparedStatement; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException;

创建javabean类 　

public class Student { private String Id; private String Name; private String Sex; private String Age; Student(String Name, String Sex, String Age) { this.Id = null; //default this.Name = Name; this.Sex = Sex; this.Age = Age; } public String getId() { return Id; } public void setId(String Id) { this.Id = Id; } public String getName() { return Name; } public void setName(String Name) { this.Name = Name; } public String getSex() { return Sex; } public void setSex(String Sex) { this.Sex = Sex; } public String getAge() { return Age; } public void setage(String Age) { this.Age = Age; } }

JDBC获取连接

private static Connection getConn() { String driver = "com.mysql.jdbc.Driver"; String url = "jdbc:mysql://localhost:3306/student"; String username = "root"; String password = "123456"; 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; }

CRUD 操作（database：student table：students）

//增 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; } ---------- //删 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; } ---------- //改 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; } ---------- //查 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(""); } } catch (SQLException e) { e.printStackTrace(); } return null; }

测试

打开mysql服务 windows命令： net start mysql测试代码： public static void main(String args[]) { JDBCOperation.getAll(); JDBCOperation.insert(new Student("Toom", "Male", "14")); JDBCOperation.getAll(); JDBCOperation.update(new Student("Bean", "Female", "7")); JDBCOperation.delete("Toom"); JDBCOperation.getAll(); }

JDBC总结

• 第一步:注册驱动 方式一：DriverManager.registerDriver(new Driver()); //通过查看源码,底层还会再次创建Driver,不推荐。 注意： 这里的new Driver()指的是—>实现类”com.mysql.jdbc.Driver()”-实现了接口 ”java.sql.Driver” 方式二： Class.forName(“驱动路径”); // com.mysql.jdbc.Driver ,开发中推荐

• 第二步:获取连接对象Connection 作用:连接数据库的对象,获取执行SQL语句的Statement对象 Connection conn = DriverManager.getConnection();

• 第三步:获取执行SQL语句的Statement

Statement stmt = conn.createStatement(); // 获取Statement对象, 存在SQL注入问题,不推荐 PreparedStatement ps = conn.prepareStatement(); //预编译对象

• 第四步:执行SQL语句

// 执行增删改查都通用 boolean b = ps.execute(); //如果第一个结果是 ResultSet 对象，则返回 true；如果第一个结果是更新计数或者没有结果，则返回 false //增删改的操作 int num = ps.executeUpdate(); //查询操作 ResultSet rs = ps.executeQuery(); //遍历结果集 while(rs.next()) { //获取记录 getInt(列的值); //int i = rs.getInt(1); getInt(列的名称); // rs.getInt("userid") getString(列的值); // String username = rs.getString(2); getString(列的名称); //String username= rs.getString("username");

• 第五步: 释放资源