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下面是簡單的數(shù)據(jù)庫操作Javabean的代碼:
| DbWrapper.java |
import java.sql.*;import java.util.*;publicclass DbWrapper
{// 定義連接池對(duì)象為靜態(tài)變量，將一直存在，直到工作目錄關(guān)閉。privatestatic DataSource ds =null;
// 1.用連接池的方式獲得連接// 如果不是做多數(shù)據(jù)庫程序，推薦使用此方法// 相關(guān)內(nèi)容：在tomcat管理界面配置連接池publicstatic Connection openConnection()throws Exception
{// 只需要初始化1次if( ds ==null){
Context initContext =newInitialContext();
Context envContext =(Context) initContext.lookup("java:/comp/env");
DataSource ds =(DataSource) envContext.lookup("jdbc/MyDataSource");}return ds.getConnection();}// 2.用jdbc驅(qū)動(dòng)獲得連接// 相關(guān)內(nèi)容：JSP數(shù)據(jù)庫連接大全publicstatic Connection openConnection(
String driver,
String url,
String username,
String password)throws Exception
{
Class.forName(driver).newInstance();return DriverManager.getConnection(url, username, password);}publicstaticvoidcloseConnection(Connection conn)throws Exception
{if( conn !=null){
conn.close();}}
publicstaticintexecuteUpdate(String sql)throws Exception
{int count =0;
Connection conn =null;
Statement stmt =null;try{
conn =openConnection();
stmt = conn.createStatement();
count = stmt.executeUpdate(sql);}catch( Exception e ){throw e;}finally{closeConnection(conn);}return count;}publicstatic List executeQuery(String sql)throws Exception
{
List list =newArrayList();
Connection conn =null;
Statement stmt =null;
ResultSet rs =null;try{
conn =openConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql);
ResultSetMetaData rsmd = rs.getMetaData();while( rs.next()){
Map map =newHashMap();for(int i =1; i <= rsmd.getColumnCount(); i++){
map.put(rsmd.getColumnName(i), rs.getObject(i));}
list.add(map);}
}catch( Exception e ){
e.printStackTrace();}finally{if( rs !=null) rs.close();closeConnection(conn);}return list;
}}
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// 1.對(duì)于insert, update, delete語句
int count = DbWrapper.executeUpdate(sql);
// 2.對(duì)于selete語句
java.util.List list = DbWrapper.executeQuery(sql);
// 方法一:按名字取值，注意大小寫是嚴(yán)格區(qū)分的for(int i =0; i < list.size(); i++){
java.util.Map map =(java.util.Map)list.get(i);
out.println(mag.get("column_name").toString());}
// 方法二：遍歷取值for(int i =0; i < list.size(); i++){
java.util.Map map =(java.util.Map)list.get(i);
for(java.util.Iterator it = map.keySet().iterator(); it.hasNext();){
String column_name = it.next().toString());
// 取值時(shí)注意null判斷
out.println(column_name +" = "+ map.get(column_name) ==null?"": map.get(column_name).toString());}}
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