JDBC从入门到熟练(二)

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import java.sql.*;import java.util.List;//Dao工厂类public class DaoFactory {private static String driver="com.microsoft.sqlserver.jdbc.SQLServerDriver";private static String url="jdbc:sqlserver://localhost:1433;DatabaseName=News";private static String sql="insert userInfo values('admin','admin',getdate())";private static String user="sa";private static String pwd="sa";//1.公共方法是获得数据库链接对象public static Connection getConnection(){Connection con=null;try {Class.forName(driver);//加,连con=DriverManager.getConnection(url,user,pwd);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}return con;//非void都需要return}//2.关闭所有方法;有3个参数!,省代码了!!!public static void closeAll(ResultSet rs,Statement stmt,Connection con){try {if(rs!=null){rs.close();}if(stmt!=null){stmt.close();}if(con!=null){con.close();}} catch (SQLException e) {e.printStackTrace();}}//3.setParams,用来设置预编译语句对象的?占位符的值;public void setParams(PreparedStatement pstmt,Object[]params){if(params==null){return; }//return:直接返回，啥也不做;try {for(int i=0;i<params.length;i++){pstmt.setObject(i+1,params[i]);}} catch (SQLException e) {//有异常,加上去e.printStackTrace();}}//4.做公共的更新方法，可以更新所有的基本sql语句;public int executeUpdate(String sql,Object[]params){//1.声明对象;是将来工作当中省内存;Connection con=null;PreparedStatement pstmt=null;int count=0; //增删改受影响的行数;try {con=this.getConnection();//调用本类的方法；pstmt=con.prepareStatement(sql);//建对象:预编译对象,?setParams(pstmt,params);//调用设置?的方法，已经写过了!!!count=pstmt.executeUpdate();//3.执行;} catch (SQLException e) {e.printStackTrace();}finally{this.closeAll(null, pstmt, con);}return count;}//5.执行查询方法;public static List executeQuery(String sql, Object[] params) {Connection con = null;PreparedStatement pstmt = null;ResultSet rs = null;int colCount = 0;ArrayList tableList=new ArrayList();//表集合try {con = getConnection();pstmt = con.prepareStatement(sql);setParams(pstmt, params);rs = pstmt.executeQuery();// 执行查询，结果给rsResultSetMetaData rd = rs.getMetaData();// 获得元数据colCount = rd.getColumnCount();while (rs.next()) {ArrayList rowList = new ArrayList();//行集合for (int i = 1; i <= colCount; i++) {rowList.add(rs.getString(i));}tableList.add(rowList);}} catch (SQLException e) {e.printStackTrace();}finally{closeAll(rs,pstmt,con);}return tableList;}}

DAO接口

import java.util.List;//针对UserInfo的增删改查接口;public interface UserInfoDAO {public int insertUserInfo(UserInfo user); //saveXXXpublic int updateUserInfo(UserInfo user);public int deleteUserInfo(UserInfo user);public List<UserInfo>queryUserInfo();//查询学生方法}

//实现类

import java.util.List;public class UserInfoDAOImpl extends DaoFactory implements UserInfoDAO {@Overridepublic int deleteUserInfo(UserInfo user) {return 0;}/* (non-Javadoc) * @see 插入方法，重写 */@Overridepublic int insertUserInfo(UserInfo user) {int result=0;String sql="";Object[]params=;result=super.executeUpdate(sql, params);return result;}@Overridepublic List<UserInfo> queryUserInfo() {String sql="select * from userinfo";List list=DaoFactory.executeQuery(sql, null);return list;}@Overridepublic int updateUserInfo(UserInfo user) {return 0;}}

测试类

package nan;import java.util.List;public class Test {public static void main(String[] args) {UserInfoDAO udd=new UserInfoDAOImpl();List tableList=udd.queryUserInfo();for(int i=0;i<tableList.size();i++){List rowList=(List)tableList.get(i);//cann't from Object to List,必须强转for(int j=0;j<rowList.size();j++){System.out.print(rowList.get(j)+"\t");}System.out.println();//每行完毕后换行}}}

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