Java增删改查功能实现代码

在Java中，数据库操作通常通过JDBC（Java Database Connectivity）连接和SQL查询来实现增删改查的功能。这里给出一个简单的例子，假设我们有一个名为"Student"的实体类，代表学生表，包含id、name和age属性：

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

public class CRUDOperations {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USER = "username";
    private static final String PASS = "password";

    // 创建一个新的学生
    public void insert(Student student) {
        String sql = "INSERT INTO students (name, age) VALUES (?, ?)";
        try (Connection connection = DriverManager.getConnection(DB_URL, USER, PASS);
             PreparedStatement statement = connection.prepareStatement(sql)) {

            statement.setString(1, student.getName());
            statement.setInt(2, student.getAge());
            statement.executeUpdate();
        } catch (Exception e) {
            System.out.println("Error inserting data: " + e.getMessage());
        }
    }

    // 更新学生信息
    public void update(Student student) {
        String sql = "UPDATE students SET name = ?, age = ? WHERE id = ?";
        try (Connection connection = DriverManager.getConnection(DB_URL, USER, PASS);
             PreparedStatement statement = connection.prepareStatement(sql)) {

            statement.setString(1, student.getName());
            statement.setInt(2, student.getAge());
            statement.setInt(3, student.getId());
            int rowsAffected = statement.executeUpdate();
            if (rowsAffected > 0) {
                System.out.println("Updated " + rowsAffected + " row(s)");
            }
        } catch (Exception e) {
            System.out.println("Error updating data: " + e.getMessage());
        }
    }

    // 删除学生
    public void delete(int id) {
        String sql = "DELETE FROM students WHERE id = ?";
        try (Connection connection = DriverManager.getConnection(DB_URL, USER, PASS);
             PreparedStatement statement = connection.prepareStatement(sql)) {

            statement.setInt(1, id);
            int rowsAffected = statement.executeUpdate();
            if (rowsAffected > 0) {
                System.out.println("Deleted " + rowsAffected + " row(s)");
            }
        } catch (Exception e) {
            System.out.println("Error deleting data: " + e.getMessage());
        }
    }

    // 查询所有学生
    public List<Student> getAll() {
        List<Student> students = new ArrayList<>();
        String sql = "SELECT * FROM students";
        try (Connection connection = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement statement = connection.createStatement()) {

            ResultSet resultSet = statement.executeQuery(sql);
            while (resultSet.next()) {
                Student student = new Student();
                student.setId(resultSet.getInt("id"));
                student.setName(resultSet.getString("name"));
                student.setAge(resultSet.getInt("age"));
                students.add(student);
            }
        } catch (Exception e) {
            System.out.println("Error fetching data: " + e.getMessage());
        }

        return students;
    }
}

这个类包含了四个静态方法分别对应增删改查操作，注意实际应用中需要处理异常并关闭资源。