JDBC Dao的实现与测试

在三层架构中，jdbc属于数据访问层。通过Domain等进行数据传递。



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

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。