时间:2021-07-01 10:21:17 帮助过:28人阅读
public class DBUtils {
private static ComboPooledDataSource comboPooledDataSource = null;
static {
//它会自动寻找配置文件,节点为mysql的数据库【如果没有指定,就使用默认的!】
comboPooledDataSource = new ComboPooledDataSource("mysql");
}
public static DataSource getDataSource() {
return comboPooledDataSource ;
}
public static Connection getConnection() {
try {
return comboPooledDataSource.getConnection();
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("数据库初始化失败了!");
}
}
}
非常简单,根据实体表来设计就好了!
CREATE TABLE user (
id VARCHAR(20) PRIMARY KEY,
username VARCHAR(20) UNIQUE NOT NULL,
password VARCHAR(20) NOT NULL,
email VARCHAR(20),
birthday DATE
);
public class UserImplDataBase implements UserDao {
@Override
public User find(String username, String password) {
return null;
}
@Override
public void register(User user) {
}
}
下面我们就直接使用DBUtils框架了
@Override
public User find(String username, String password) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "SELECT * FROM user WHERE username=? AND password=?";
try {
User user = (User) queryRunner.query(sql, new BeanHandler(User.class), new Object[]{username, password});
return user == null ? null : user;
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("登陆失败了!");
}
}
@Override
public void register(User user) {
QueryRunner queryRunner = new QueryRunner(Utils2DB.getDataSource());
String sql = "INSERT INTO user (id, username, password, email,birthday) VALUES (?,?,?,?,?);";
String id = user.getId();
String username = user.getUsername();
String password = user.getPassword();
String email = user.getEmail();
Date date = user.getBirthday();
try {
queryRunner.update(sql, new Object[]{id, username, password, email,date});
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException("注册失败了");
}
}
}
我们的Dao实现已经有了XML版和JDBC版的,BusinessService调用Dao层方法的时候还是要new出具体的Dao实现,也就是以下的代码:
UserDao userDao = new UserImplXML();
//或者
UserDao userDao= new UserImplDataBase();
这样做有点不够灵活,也就有点不够专业!下面我们来说一下为什么需要DaoFactory?
参考博文:http://blog.sina.com.cn/s/blog_4ca34d0501008tpc.html
摘抄重点:
优点:
缺点:
首先,我们把DaoFactory设计成单例的【工厂有一个就够了!】
public class DaoFactory {
private DaoFactory() {
}
private static final DaoFactory DAO_FACTORY = new DaoFactory();
//暴露公开方法获取工厂对象
public static DaoFactory newInstance() {
return DAO_FACTORY;
}
}
目前我们操作的是User,所以工厂造UserDao对象,而UserDao对象是JDBC版呢,还是XML版呢,我们通过配置文件来定(这样就更灵活了)!
#class需要的是完整的对象名称(包括包)
#userClass=zhongfucheng.dao.impl.UserImplDataBase
userClass=zhongfucheng.dao.impl.UserImplXML
private static UserDao userDao = null;
private DaoFactory() {
try {
//读取配置文件的信息
InputStream inputStream = DaoFactory.class.getClassLoader().getResourceAsStream("UserDao.properties");
Properties properties = new Properties();
properties.load(inputStream);
String userClass = properties.getProperty("userClass");
//利用反射机制创建相对应的对象
userDao = (UserDao) Class.forName(userClass).newInstance();
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException("读取文件失败了!");
} catch (IllegalAccessException e) {
e.printStackTrace();
throw new RuntimeException("反射失败了!");
} catch (InstantiationException e) {
e.printStackTrace();
throw new RuntimeException("反射失败了!");
} catch (ClassNotFoundException e) {
e.printStackTrace();
throw new RuntimeException("反射失败了!");
}
}
public static UserDao createUserDao() {
return userDao;
}
UserDao userDao = DaoFactory.newInstance().createUserDao();
如果我们的mysql驱动版本太低,就出现以下的异常!我们只需要下载新的mysql的jar包,导入项目即可!
java.sql.SQLException: Feature not implemented Query:insert into guestbook (id,name,email,url,title,content,time) value(?,?,?,?,?,?,?) Parameters: [1, qwq,wqwq,qwqw,qw,qw, 2010-09-13]
JDBC版的成功的效果如下:
XML版的成功效果如下:
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用户登陆注册【JDBC版】
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