JDBC增、删、改、查操作

public class JdbcUserDaoImpl implements UserDao {
//添加用户操作
public void addUser(User form) {
Connection con = null;
PreparedStatement pstmt = null;
try {
// 一、得到连接
con = JdbcUtils.getConnection();
// 二、准备sql模板，得到pstmt
String sql = "INSERT INTO t_user VALUES(?,?,?,?)";
pstmt = con.prepareStatement(sql);
// 三、为pstmt中的问号赋值
pstmt.setString(1, form.getUsername());
pstmt.setString(2, form.getPassword());
pstmt.setInt(3, form.getAge());
pstmt.setString(4, form.getGender());
// 四、执行之
pstmt.executeUpdate();
} catch(Exception e) {
throw new RuntimeException(e);
} finally {
try {
if(pstmt != null) pstmt.close();
if(con != null) con.close();
} catch(SQLException e) {}
}
}

//查询操作
public User findByUsername(String username) {
Connection con = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
try {
// 一、得到连接
con = JdbcUtils.getConnection();
// 二、准备sql模板，得到pstmt
String sql = "SELECT * FROM t_user WHERE username=?";
pstmt = con.prepareStatement(sql);
// 三、为pstmt中的问号赋值
pstmt.setString(1, username);
// 四、执行之
rs = pstmt.executeQuery();
// 五、把rs转换成User类型，返回！
if(rs == null) {
return null;
}
if(rs.next()) {
//转换成User对象，并返回
// ORM --> 对象关系映射！ hibernate!
User user = new User();
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setAge(rs.getInt("age"));
user.setGender(rs.getString("gender"));
return user;
} else {
return null;
}
} catch(Exception e) {
throw new RuntimeException(e);
} finally {
try {
if(pstmt != null) pstmt.close();
if(con != null) con.close();
} catch(SQLException e) {}
}
}
}