分层结构DAO层

DAO（Date Access Object）模型就是写一个类，把访问数据库的代码封装起来，DAO在数据库与业务逻辑（Service）之间。

1、实体域，即操作的对象，例如我们操作的表示user表，那么就需要先写一个User类；
2、DAO模型需要先提供一个DAO接口；
3、然后再提供一个DAO接口的实现类；
4、再编写一个DAO工厂，Service通过工厂来获取DAO

一. BaseDAO类主要连接数据库和数据库之间进行交互

public class BaseDAO {
   private static final String driver="com.mysql.jdbc.Driver";
   private static final String url="jdbc:mysql:///newss2230";
   private static final String username="root";
   private static final String password="123";

   Connection con;
   PreparedStatement ps;
   ResultSet rs;


   public Connection getConnection() throws Exception{
    Class.forName(driver);
    if(con==null||con.isClosed()){
     con=DriverManager.getConnection(url, username, password);
    }
    /*Context context=new InitialContext();
    DataSource ds=(DataSource)context.lookup("java:comp/env/news");
    con=ds.getConnection();*/
    return con;
   }
   public int executeUpdate(String sql,Object...paras) throws Exception{
    getConnection();
     ps= con.prepareStatement(sql);
     for (int i = 0; i < paras.length; i++) {
   ps.setObject(i+1, paras[i]);
  }
     int count = ps.executeUpdate();
     return count;
   }

   public ResultSet executeQuery(String sql,Object...paras) throws Exception{
    getConnection();
     ps= con.prepareStatement(sql);
     for (int i = 0; i < paras.length; i++) {
   ps.setObject(i+1, paras[i]);
  }
     return ps.executeQuery();
   }
   public void closeResource(){
    try {
     if(rs!=null){
      rs.close();
     }
     if(ps!=null){
      ps.close();
     }
     if(con!=null){
      con.close();
     }
} catch (Exception e) {
}

   }

}

二.IUserInfoDAO接口（登陆接口）

public interface IUserInfoDAO {
//01.写一个登录系统的方法
public UserInfo isLogin(UserInfo info) throws Exception;
//02.写一个查询所有用户信息的方法
public List<UserInfo> findAll() throws Exception;
public boolean delete(Integer uid) throws Exception;
public boolean addUser(UserInfo info)throws Exception;
public UserInfo updateshow(Integer uid)throws Exception;
public boolean updateUser(UserInfo userinfo)throws Exception;
}

三.UserInfoDAOImpl实现类

public class UserInfoDAOImpl extends BaseDAO implements IUserInfoDAO {
@Test
public void testLogin() throws Exception{
  UserInfo info=new UserInfo();
  info.setUname("admin");
  info.setUpwd("admin");
  UserInfo result=isLogin(info);
  if (result!=null) {
   System.out.println("success");
  }else{
   System.out.println("failed");
  }

}

@Override
public UserInfo isLogin(UserInfo info) throws Exception {
     String sql="select * from userinfo where uname=? and upwd=?";
     Object[] paras={info.getUname(),info.getUpwd()};
     ResultSet rs = executeQuery(sql, paras);

     UserInfo userinfo=null;
     if(rs!=null){
     if(rs.next()){
       //如果有Data ，取出该行，每个列的值，赋值给单个UserInfo实例的对应属性
       userinfo=new UserInfo();
       userinfo.setUid(rs.getInt("uid"));
       userinfo.setUname(rs.getString("uname"));
       userinfo.setUpwd(rs.getString("upwd"));
     }
     closeResource();
     }
  return userinfo;
}

@Override
public List<UserInfo> findAll() throws Exception {
  List<UserInfo> list=new ArrayList<UserInfo>();
  String sql="select * from userinfo";
  ResultSet rs = executeQuery(sql);
  UserInfo userinfo=null;
     if(rs!=null){
     while(rs.next()){
       //如果有Data ，取出该行，每个列的值，赋值给单个UserInfo实例的对应属性
       userinfo=new UserInfo();
       userinfo.setUid(rs.getInt("uid"));
       userinfo.setUname(rs.getString("uname"));
       userinfo.setUpwd(rs.getString("upwd"));
       list.add(userinfo);
     }
     closeResource();
     }
  return list;
}

@Override
public boolean delete(Integer uid) throws Exception {
  boolean flag=false;
  String sql="delete from userinfo where uid=?";
  int count = executeUpdate(sql, uid);
  if (count>0) {
   flag=true;
  }
  return flag;
}

@Override
public boolean addUser(UserInfo info) throws Exception {
  boolean flag=false;//添加失败
  String sql="insert into userinfo(uname,upwd) values(?,?)";
  Object[] paras={info.getUname(),info.getUpwd()};
  int count = executeUpdate(sql, paras);
  if (count>0) {
   flag=true;
  }
  return flag;
}

@Override
/**
* 根据主键获取单个对象
*/
public UserInfo updateshow(Integer uid) throws Exception {
  UserInfo userinfo = new UserInfo();
  String sql="select * from userinfo where uid = ?";
  ResultSet rs = this.executeQuery(sql, uid);
  if(rs!=null){
   if(rs.next()){
    userinfo.setUid(rs.getInt("uid"));
    userinfo.setUname(rs.getString("uname"));
    userinfo.setUpwd(rs.getString("upwd"));
   }
   closeResource();
  }
  return userinfo;
}

@Override
public boolean updateUser(UserInfo userinfo) throws Exception {
  boolean flag=false;
  String sql="update userinfo set uname=?,upwd=? where uid=?";
  Object[] paras={userinfo.getUname(),userinfo.getUpwd(),userinfo.getUid()};
  int count = executeUpdate(sql, paras);
  if (count>0) {
   flag=true;
  }
  return flag;
}

}