关于EJB返回值的最好的解决方案
相信很多人都有如此之困惑，得此解决方法不敢独享，公之于众，以利后来人。
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，如果去查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:
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:\jdk1.4\jre\rowset.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非常相似，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()); } } } |
cheers.
Robin
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