05-c3p0连接池

1. 导入 jar 包

jar包下载地址：https://mvnrepository.com/

导入IDEA，位置：project\lib

2. 配置文件

位置：project\src\c3p0.properties

# MySQL c3p0 数据库配置
c3p0.driverClass=com.mysql.jdbc.Driver
c3p0.jdbcUrl=jdbc:mysql://localhost:3306/数据库名
c3p0.user=root
c3p0.password=123456

3. 连接池工具类

C3P0DbUtils.java

import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3P0DbUtils {
    private static ComboPooledDataSource dataSource;
    static {
        dataSource = new ComboPooledDataSource();
    }

    public static ComboPooledDataSource getDataSource() {
        return dataSource;
    }
}

4. 执行SQL语句

public class UserDaoImpl implements UserDao {
    private QueryRunner queryRunner = new QueryRunner(C3P0dbUtils.getDataSource());

    /**
     * 增删改操作
     * @param action 字符串insert/delete/update
     * @param user 操作的用户
     * @return 影响结果行
     */
    @Override
    public int update(String action, User user) throws SQLException {
        if (null == action) {
            return -1;
        }

        String sql = null;
        Object[] args = null;
        if ("insert".equals(action)) {
            sql = "insert into userinfo(username, password) value(?,?)";
            args = new Object[]{user.getUsername(), user.getPassword()};
        } else if ("delete".equals(action)) {
            sql = "delete from userinfo where id=?";
            args = new Object[]{user.getId()};
        } else if ("update".equals(action)) {
            sql = "update userinfo set username=?,password=? where id=?";
            args = new Object[]{user.getUsername(), user.getPassword(), user.getId()};
        } else {
            return -1;
        }
        System.out.println("sql=" + sql);
        System.out.println("args=" + args);
        return queryRunner.update(Objects.requireNonNull(sql), args);
    }

    /**
     * 查单个
     * @param id 编号
     * @return 用户对象
     */
    @Override
    public User select(Integer id) throws SQLException {
        return queryRunner.query(
                "select * from userinfo where id=?",
                new BeanHandler<>(User.class),
                id
        );
    }

    /**
     * 查所有
     * @return 对象表
     */
    @Override
    public List<User> selectALL() throws SQLException {
        return queryRunner.query(
                "select * from userinfo",
                new BeanListHandler<>(User.class)
        );
    }
}