java增删改查经典案例

Java中的经典增删改查案例包括以下几种：

1. 基于JDBC的增删改查

使用JDBC连接数据库，执行SQL语句进行增删改查操作。示例代码如下：

import java.sql.*;

public class JdbcDemo {

    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            // 1. 加载驱动
            Class.forName("com.mysql.jdbc.Driver");

            // 2. 获取连接
            String url = "jdbc:mysql://localhost:3306/test";
            String username = "root";
            String password = "123456";
            conn = DriverManager.getConnection(url, username, password);

            // 3. 执行SQL语句
            // 插入数据
            String sql = "insert into user(name, age) values(?, ?)";
            ps = conn.prepareStatement(sql);
            ps.setString(1, "张三");
            ps.setInt(2, 20);
            ps.executeUpdate();

            // 查询数据
            sql = "select * from user";
            ps = conn.prepareStatement(sql);
            rs = ps.executeQuery();
            while (rs.next()) {
                System.out.println(rs.getInt("id") + "\t" + rs.getString("name") + "\t" + rs.getInt("age"));
            }

            // 更新数据
            sql = "update user set age=? where name=?";
            ps = conn.prepareStatement(sql);
            ps.setInt(1, 25);
            ps.setString(2, "张三");
            ps.executeUpdate();

            // 删除数据
            sql = "delete from user where name=?";
            ps = conn.prepareStatement(sql);
            ps.setString(1, "张三");
            ps.executeUpdate();

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 4. 释放资源
            try {
                if (rs != null) {
                    rs.close();
                }
                if (ps != null) {
                    ps.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

2. 基于MyBatis的增删改查

使用MyBatis ORM框架进行数据库操作。示例代码如下：

import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MybatisDemo {

    public static void main(String[] args) {
        // 1. 加载配置文件
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builder.build(MybatisDemo.class.getClassLoader().getResourceAsStream("mybatis-config.xml"));

        // 2. 获取SqlSession
        SqlSession session = factory.openSession();

        try {
            // 3. 执行SQL语句
            // 插入数据
            User user = new User();
            user.setName("张三");
            user.setAge(20);
            session.insert("UserMapper.insert", user);

            // 查询数据
            List<User> users = session.selectList("UserMapper.selectAll");
            for (User u : users) {
                System.out.println(u.getId() + "\t" + u.getName() + "\t" + u.getAge());
            }

            // 更新数据
            User updateUser = new User();
            updateUser.setName("张三");
            updateUser.setAge(25);
            session.update("UserMapper.update", updateUser);

            // 删除数据
            session.delete("UserMapper.delete", "张三");

            // 提交事务
            session.commit();
        } catch (Exception e) {
            // 回滚事务
            session.rollback();
            e.printStackTrace();
        } finally {
            // 4. 释放资源
            session.close();
        }
    }
}

3. 基于Spring JDBC的增删改查

使用Spring JDBC模块进行数据库操作。示例代码如下：

import java.util.List;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

public class SpringJdbcDemo {

    public static void main(String[] args) {
        // 1. 创建数据源
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/test");
        dataSource.setUsername("root");
        dataSource.setPassword("123456");

        // 2. 创建JdbcTemplate对象
        JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);

        try {
            // 3. 执行SQL语句
            // 插入数据
            String sql = "insert into user(name, age) values(?, ?)";
            jdbcTemplate.update(sql, "张三", 20);

            // 查询数据
            sql = "select * from user";
            List<User> users = jdbcTemplate.query(sql, new UserRowMapper());
            for (User u : users) {
                System.out.println(u.getId() + "\t" + u.getName() + "\t" + u.getAge());
            }

            // 更新数据
            sql = "update user set age=? where name=?";
            jdbcTemplate.update(sql, 25, "张三");

            // 删除数据
            sql = "delete from user where name=?";
            jdbcTemplate.update(sql, "张三");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static class UserRowMapper implements RowMapper<User> {

        @Override
        public User mapRow(ResultSet rs, int rowNum) throws SQLException {
            User user = new User();
            user.setId(rs.getInt("id"));
            user.setName(rs.getString("name"));
            user.setAge(rs.getInt("age"));
            return user;
        }
    }
}