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有两种方式: 1、用vector: public Enumeration ejbFindBigAccounts(double balanceGreaterThan) { log("ejbFindBigAccounts (balance " + balanceGreaterThan + ")"); Connection con = null; PreparedStatement ps = null; try { con = getConnection(); ps = con.prepareStatement("select id from ejbAccounts where bal ?"); ps.setDouble(1, balanceGreaterThan); ps.executeQuery(); ResultSet rs = ps.getResultSet(); Vector v = new Vector(); String pk; while (rs.next()) { pk = rs.getString(1); v.addElement(pk); } return v.elements(); } catch (SQLException sqe) { log("SQLException: " + sqe); throw new EJBException (sqe); } finally { cleanup(con, ps); } } 结论:不爽,不方便。 2、RowSet RowSet tutorial chapter : http://developer.java.sun.com/developer/Books/JDBCTutorial/chapter5.html rowset是个interface,需要有东西去实现它,sun的规范中给了三个class:cachedrowset,jdbcrowset,webrowset, 假如去查jdk1.4 doc和j2skee1.2,有rowset,却没有那三个class,一般的开发工具(至少我的wsad)中也是这样, 所以需要下jdbc2.0 opt-pack: http://developer.java.sun.com/developer/earlyAccess/crs/ 下下来了再怎么办呢? 装呗! 怎么装呢? setup呀! 没有呀? 啊,没setup呀,sun干什么吃的,连setup都不做个,也太懒了吧。 ///////////////////////////////// 哎,我们确实是都被ms惯坏了,看到只有jar,没setup就没辙了,大家好好想想,java最大的特性是什么,就是它的类库 可以自由扩充呀,现在明白该怎么做了吧: 1、解包,得到rowset.jar,放在哪随您的意,别丢了就行。 2、在您的开发工具中增加一个路径,如:ROWSET_PATH对应:d:jdk1.4jre owset.jar(和1的路径对应就行)。 3、右键您的工程文件,出现:property(大多数工具应该都有吧),加上rowset_path。 4、在您的源文件中:import sun.jdbc.rowset.*; OK,搞定!下面就看您的了。(当然也可以把rowset压到jre里去) 应该说rowset(其实主要是CachedRowSet)真的是个好东西,和ms ado的resultset和borland的tclientset异常相似, 最大的好处是Cache功能! 好了,看例子吧: /////////////server端///////////// package example4; import java.sql.*; import javax.sql.*; import sun.jdbc.rowset.*; import javax.naming.*; import javax.ejb.*; public class CoffeesBean implements SessionBean { private SessionContext sc = null; private Context ctx = null; private DataSource ds = null; public CoffeesBean () {} public void ejbCreate() throws CreateException { try { ctx = new InitialContext(); ds = (DataSource)ctx.lookup("jdbc/CoffeesDB"); } catch (Exception e) { System.out.println(e.getMessage()); throw new CreateException(); } } public RowSet getCoffees() throws SQLException { Connection con = null; ResultSet rs; CachedRowSet crs; try { con = ds.getConnection("webCustomer", "webPassword"); Statement stmt = con.createStatement(); rs = stmt.executeQuery("select * from coffees"); crs = new CachedRowSet(); crs.populate(rs); // the writer needs this because JDBC drivers // don´t provide this meta-data. crs.setTableName("coffees"); rs.close(); stmt.close(); } finally { if (con != null) con.close(); } return rset; } public updateCoffees(RowSet rs) throws SQLException { Connection con = null; try { CachedRowSet crs = (CachedRowSet)rs; con = ds.getConnection("webCustomer", "webPassword"); moves the changes back to the database crs.acceptChanges(con); } finally { if (con != null) con.close(); } } // // Methods inherited from SessionBean // public void setSessionContext(SessionContext sc) { this.sc = sc; } public void ejbRemove() {} public void ejbPassivate() {} public void ejbActivate() {} } //////////////////client端////////////// package example4; import java.sql.*; import javax.sql.*; import sun.jdbc.rowset.*; import javax.naming.*; import javax.ejb.*; import javax.rmi.*; class CoffeesClient { public static void main(String[] args) { try { // init the bean Context ctx = new InitialContext(); Object obj = ctx.lookup("ejb/Coffees"); CoffeesHome coffeesHome = (CoffeesHome) PortableRemoteObject.narrow(obj, CoffeesHome.class); Coffees coffees = coffeesHome.create(); // get the rowset from the bean CachedRowSet rset = (CachedRowSet)coffees.getCoffees(); // find the Columbian coffee while (rset.next()) { String coffeeName = rset.getString("COF_NAME"); if (coffeeName.equalsIgnoreCase(new String("Columbian"))) { // columbian coffee has gone up 10% rset.updateFloat("PRICE", (float)(rset.getFloat("PRICE") * 1.10)); rset.updateRow(); } } // finally send the updated back to the bean... System.out.println("Calling update method"); coffees.updateCoffees((RowSet)rset); } catch (Exception e) { System.out.println(e.getMessage()); } } } 例子很简朴就不多讲了。 返回类别: 教程 上一教程: 利用UDP SOCKETS技术实现IP多点传送 下一教程: JSP源码实例 您可以阅读与"分布式数据库客户端数据集的选用"相关的教程: · 如何调出cloudscape数据库的图形治理界面及相关问题 · JSP页面连接MYSQL数据库 · 漫谈JAVA数据库存取技术 · JSP中TOMCAT的SQL SERVER2000数据库连接池的配置 · 从oracle 数据库读取日期时间,并在网页上打印万年历 |
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