JDBC Dao的实现与测试

- 日理万妓 2022-08-09 00:52 128阅读 0赞

在三层架构中，jdbc属于数据访问层。通过Domain等进行数据传递。  
![三层架构][20151001112157508]  
各个层之间最好能相互独立。  
建立一个UserDao，通过他来传递对象（Dao：Data Access Object数据访问对象）

//User.java
    //存储数据的model
    package cn.itcast.domain;
    
    import java.util.Date;
    
    public class User { 
        private int id;
        private String name;
        private Date birthday;
        private float money;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public Date getBirthday() {
            return birthday;
        }
        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }
        public float getMoney() {
            return money;
        }
        public void setMoney(float money) {
            this.money = money;
        }
    }

//UserDao.java
    //Dao interface访问数据库
    package cn.itcast.jdbc.dao;
    
    import cn.itcast.domain.User;
    
    public interface UserDao { 
        public void addUser(User user);
        public User getUser(int userId);
        public User findUser(String loginNames,String password);
        public void update(User user);
        public void delete(User user);
    }

//UserDaoJdbcImpl.java
    //UserDao的实现
    package cn.itcast.dao.Impl;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    import cn.itcast.domain.User;
    import cn.itcast.jdbc.JdbcUtils;
    import cn.itcast.jdbc.dao.UserDao;
    
    public class UserDaoJdbcImpl implements UserDao { 
    
        //增
        @Override
        public void addUser(User user) {
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
    
            try {
                conn = JdbcUtils.getConnection();
                String sql = "insert into user(name,birthday,money)values(?,?,?)";
                ps = conn.prepareStatement(sql);
                ps.setString(1, user.getName());
                ps.setDate(2, new java.sql.Date(user.getBirthday().getTime()));
                ps.setFloat(3, user.getMoney());
                ps.executeUpdate();
            } catch (SQLException e) {
                throw new DaoException(e.getMessage(), e);
            } finally {
                JdbcUtils.free(rs, ps, conn);
            }
        }
    
        //根据userId查找user
        @Override
        public User getUser(int userId) {
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
            User user = null;
    
            try {
                conn = JdbcUtils.getConnection();
                String sql = "select id,name,birthday,money from user where id=?";
                ps = conn.prepareStatement(sql);
                ps.setInt(1, userId);
                rs = ps.executeQuery();
                while (rs.next()) {
                    user = mappingUser(rs);
                }
            } catch (SQLException e) {
                throw new DaoException(e.getMessage(), e);
            } finally {
                JdbcUtils.free(rs, ps, conn);
            }
            return user;
        }
    
        // 改
        @Override
        public void update(User user) {
            Connection conn = null;
            PreparedStatement ps = null;
            ResultSet rs = null;
    
            try {
                conn = JdbcUtils.getConnection();
                String sql = "update user set name=?,birthday=?,money=? where id=?";
                ps = conn.prepareStatement(sql);
                ps.setString(1, user.getName());
                ps.setDate(2, new java.sql.Date(user.getBirthday().getTime()));
                ps.setFloat(3, user.getMoney());
                ps.setInt(4, user.getId());
                ps.executeUpdate();
            } catch (SQLException e) {
                throw new DaoException(e.getMessage(), e);
            } finally {
                JdbcUtils.free(rs, ps, conn);
            }
        }
    
        //删
        @Override
        public void delete(User user) {
            Connection conn = null;
            Statement st = null;
            ResultSet rs = null;
    
            try {
                conn = JdbcUtils.getConnection();
                st = conn.createStatement();
                String sql = "delete from user where id=" + user.getId();
                st.executeUpdate(sql);
            } catch (SQLException e) {
                throw new DaoException(e.getMessage(), e);
            } finally {
                JdbcUtils.free(rs, st, conn);
            }
        }
    
        //映射 将结果集映射为User
        private User mappingUser(ResultSet rs) throws SQLException {
            User user;
            user = new User();
            user.setId(rs.getInt("id"));
            user.setName(rs.getString("name"));
            user.setMoney(rs.getFloat("money"));
            user.setBirthday(rs.getDate("birthday"));
            return user;
        }
    }

[上面用到的DaoException][DaoException]

以上Dao及其实现已经是比较规范的代码了，可以在较小的程序中使用。

[20151001112157508]: /images/20220731/9ace3def3f5b4719b8c532dea737345e.png
[DaoException]: http://blog.csdn.net/taoxiuxia/article/details/48845525