JavaWeb開發之JDBC的增刪改查

項目搭建的包命名和類命名：

 

首先導入數據庫的驅動架包，並添加依賴

 

 

1.Dao層是專門負責和數據庫交互，數據處理的代碼層

2.Dao是接口，DaoImpl是Dao接口的實現類

3.Java代碼連接數據庫的步驟：“賈璉欲執事”口訣

　　（1）賈：加載數據庫注冊驅動,將數據庫驅動注冊到DriverManager中去。

　　　　Class.forName("com.mysql.jdbc.Driver");

 

　　（2）璉：創建連接數據庫的對象，通過DriverManager獲取

　　Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "123456");

 

　　（3）欲：創建預編譯或非預編譯 SQL語句對象

　　String sql="update t_student set name = ?,age = ? where id = ?";

　　PrepardStatment ps =conn.preparedStatment(sql);

　　ps.setString(1，"小明");

　　ps.setInt(2，20)；

　　ps.setInt(3，2)；

 

　　（4）執：執行SQL語句

　　int row =ps.executeUpdate();

 

　　（5）事：釋放資源（先創后放）

　　conn.close();

　　ps.close();

　

具體代碼：

	@Override
	public int insert(Student stu) {

		String sql = "insert into t_student(name,age)values(?,?)";
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			// 1.加載注冊驅動
			Class.forName("com.mysql.jdbc.Driver");

			// 2.獲取數據庫連接對象
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "root");
			// 3.創建預編譯語句對象
			ps = conn.prepareStatement(sql);

			// 3.1設置預編譯語句對象占位符對應的參數值
			ps.setString(1, stu.getName());
			ps.setInt(2, stu.getAge());
			// 4.執行SQL語句 (注意：方法不能帶sql參數)
			int row = ps.executeUpdate();
			return row;

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (ps != null) {
					ps.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if (conn != null) {
						conn.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
		return 0;
	}

	@Override
	public int delete(Integer id) {
		String sql = "delete from t_student where id = ?";
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			// 1.加載注冊驅動
			Class.forName("com.mysql.jdbc.Driver");

			// 2.獲取數據庫連接對象
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "root");
			// 3.創建預編譯語句對象
			ps = conn.prepareStatement(sql);

			// 3.1設置預編譯語句對象占位符對應的參數值
			ps.setInt(1, id);
			// 4.執行SQL語句 (注意：方法不能帶sql參數)
			int row = ps.executeUpdate();
			return row;

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (ps != null) {
					ps.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if (conn != null) {
						conn.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
		return 0;
	}

	@Override
	public int update(Student stu) {
		String sql = "update t_student set name = ?,age = ? where id = ?";
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			// 1.加載注冊驅動
			Class.forName("com.mysql.jdbc.Driver");

			// 2.獲取數據庫連接對象
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "root");
			// 3.創建預編譯語句對象
			ps = conn.prepareStatement(sql);

			// 3.1設置預編譯語句對象占位符對應的參數值
			ps.setString(1, stu.getName());
			ps.setInt(2, stu.getAge());
			ps.setInt(3, stu.getId());
			// 4.執行SQL語句 (注意：方法不能帶sql參數)
			int row = ps.executeUpdate();
			return row;

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (ps != null) {
					ps.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if (conn != null) {
						conn.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}
		}
		return 0;
	}

	@Override
	public Student selectByPrimaryKey(Integer id) {

		String sql = "select * from t_student where id = ?";

		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			// 1.加載注冊驅動
			Class.forName("com.mysql.jdbc.Driver");
			// 2.獲取數據庫連接對象
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "root");
			// 3.創建預編譯語句對象
			ps = conn.prepareStatement(sql);
			ps.setInt(1, id);
			// 4.執行sql語句
			rs = ps.executeQuery();

			while (rs.next()) {
				String name = rs.getString("name");
				int age = rs.getInt("age");

				// 封裝Student對象
				Student stu = new Student(id, name, age);
				//返回Student對象
				return stu;
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (rs != null) {
					rs.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if (ps != null) {
						ps.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					try {
						if (conn != null) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}
			}
		}
		return null;
	}

	@Override
	public List<Student> selectList() {

		List<Student> students = new ArrayList<>();

		String sql = "select * from t_student";

		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			// 1.加載注冊驅動
			Class.forName("com.mysql.jdbc.Driver");
			// 2.獲取數據庫連接對象
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbcdemo", "root", "root");
			// 3.創建預編譯語句對象
			ps = conn.prepareStatement(sql);

			// 4.執行sql語句
			rs = ps.executeQuery();

			while (rs.next()) {
				int id = rs.getInt("id");
				String name = rs.getString("name");
				int age = rs.getInt("age");

				// 封裝Student對象
				Student stu = new Student(id, name, age);

				// 學生對象添加到集合中
				students.add(stu);
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (rs != null) {
					rs.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			} finally {
				try {
					if (ps != null) {
						ps.close();
					}
				} catch (SQLException e) {
					e.printStackTrace();
				} finally {
					try {
						if (conn != null) {
							conn.close();
						}
					} catch (SQLException e) {
						e.printStackTrace();
					}
				}
			}
		}

		return students;
	}