数据库工具类（UserDao）

public interface InUserDao {
public boolean findUser(String name,String password);
public void addUser(User user);
public void del(int id);
public User getUserByid(int id);
public User getUserByid(String id);
public void upDataUser(User user);
public List<User> getAllUser();

}

public class userDao implements InUserDao{

@Override
public boolean findUser(String name, String password) {
JdbcHelper helo=JdbcHelper.getInstance();
boolean isexist=false;
Connection conn=helo.getConnection();
ResultSet reset=helo.executeQuery(conn,"select * from test_user where name=? and password=?", new String[]{name,password});
try {
isexist=reset.next();
} catch (SQLException e) {
e.printStackTrace();
}finally{
helo.closeResult(reset);
helo.closeConn(conn);
}
return isexist;
}
@Override
public void addUser(User user) {
JdbcHelper helo=JdbcHelper.getInstance();
helo.executeDml("insert into  test_user values(test_user_seq.nextval,?,?)", new String[]{user.getUsername(),user.getPassword()});
}

@Override
public void del(int id) {
JdbcHelper helo=JdbcHelper.getInstance();
helo.executeDml("delete  test_user  where id=?", new String[]{String.valueOf(id)});
}

封装好的数据库及user类方法以供外界查询：
@Override
public User getUserByid(String id) {
User user=new User();
JdbcHelper helo=JdbcHelper.getInstance();
Connection conn=helo.getConnection();
ResultSet reset=helo.executeQuery(conn,"select * from test_user where id=?", new String[]{id});
try {
while(reset.next()){
user.setId(reset.getInt(1));
user.setUsername(reset.getString(2));
user.setPassword(reset.getString(3));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
helo.closeResult(reset);
helo.closeConn(conn);
}
return user;
}

@Override
public void upDataUser(User user) {
JdbcHelper helo=JdbcHelper.getInstance();
helo.executeDml("update test_user set name=?,password=? where id=?", new String[]{user.getUsername(), user.getPassword(),String.valueOf(user.getId())});
}

public List<User> getAllUser(){

List<User> users=new ArrayList<User>();

JdbcHelper helo=JdbcHelper.getInstance();
Connection conn=helo.getConnection();
ResultSet reset=helo.executeQuery(conn,"select * from test_user", null);
try {
while(reset.next()){
User user=new User();
user.setId(reset.getInt(1));
user.setUsername(reset.getString(2));
user.setPassword(reset.getString(3));
users.add(user);
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
helo.closeResult(reset);
helo.closeConn(conn);
}
return users;
}

@Override
public User getUserByid(int id) {
return getUserByid(String.valueOf(id));
}

}