任務四新聞發(fā)布系統(tǒng)－訪問數(shù)據(jù)庫實驗2封裝數(shù)據(jù)庫連接類實驗目的：1.掌握如何封閉數(shù)據(jù)庫連接類掌握數(shù)據(jù)庫相關(guān)數(shù)據(jù)的增刪改查的方法實驗步驟：新建一個類，命名為BaseDao.java定義數(shù)據(jù)庫連接所需屬性值或變量 privatestaticfinalStringDRIVER="com.mysql.jdbc.Driver";// privatestaticfinalStringURL="jdbc:mysql://localhost:3306/news_2023";// privatestaticfinalStringUNAME="root";// privatestaticfinalStringUPWD="123456";// protectedConnectioncon;// protectedPreparedStatementpstm;// protectedStatementstmt;// protectedResultSetrs;//3.創(chuàng)建數(shù)據(jù)庫連接的方法 protectedvoidgetConnection()throwsException{ Class.forName(DRIVER); con=DriverManager.getConnection(URL,UNAME,UPWD); }4.創(chuàng)建關(guān)閉連接對象的方法 protectedvoidcloseAll(){ if(rs!=null){ try{ rs.close(); }catch(SQLExceptione){ e.printStackTrace(); } } if(pstm!=null){ try{ pstm.close(); }catch(SQLExceptione){ e.printStackTrace(); } } if(stmt!=null){ try{ stmt.close(); }catch(SQLExceptione){ e.printStackTrace(); } } try{ if(con!=null&&con.isClosed()==false){ con.close(); } }catch(SQLExceptione){ e.printStackTrace(); } }新建Type類publicclassType{privateintt_id;privateStringt_name;privateStringt_memo;publicType(){}publicType(intt_id,Stringt_name,Stringt_memo){this.t_id=t_id;this.t_name=t_name;this.t_memo=t_memo;}publicintgetT_id(){returnt_id;}publicvoidsetT_id(intt_id){this.t_id=t_id;}publicStringgetT_name(){returnt_name;}publicvoidsetT_name(Stringt_name){this.t_name=t_name;}publicStringgetT_memo(){returnt_memo;}publicvoidsetT_memo(Stringt_memo){this.t_memo=t_memo;}}新建TypeDao類（用于對新聞類型數(shù)據(jù)表的查詢操作）publicclassTypeDaoextendsBaseDao{publicListsearch(){ Listlist=newArrayList(); Stringsql="select*fromnrc_type"; try{ super.getConnection(); pstm=con.prepareStatement(sql); rs=pstm.executeQuery(); while(rs.next()){ Typetype=newType(); type.setT_id(rs.getInt(1)); type.setT_name(rs.getString(2)); type.setT_demo(rs.getString(3)); list.add(type); } }catch(Exceptione){ //TODOAuto-generatedcatchblock e.printStackTrace(); }finally{ super.closeAll(); } returnlist; }7、使用測試類測試數(shù)據(jù)庫訪問與結(jié)果數(shù)據(jù)顯示publicclassTest03{publicstaticvoidmain(String[]args)throwsException{TypeDaotypeDao=newTypeDao();ListtypeList=newArrayList();typeList=(ArrayList)typeDao