程序员网: 关于EJB返回值的解决方案

关于EJB返回值的解决方案

04:00

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。声明：此方法的至于彭璐大侠，彭大侠可能不常上网，这麽好的方法也不告诉我等之小虾米，只好代劳了，彭大侠的email不便公开，应该是金蝶的人吧。好了，不废话了，有两种方法： 1、用vector:


/** 
> * Finds all EJBeans with a balance greater than a given amount. 
> * Returns an Enumeration of found EJBean primary keys. 
> * 
> * @param balanceGreaterThan double Test Amount 
> * @return Enumeration EJBean Primary Keys 
> * @exception javax.ejb.EJBException 
> * if there is a communications or systems failure 
> */ 
> 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，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: 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()); 
       } 
   } 
}

例子很简单就不多讲了。 cheers. Robin Any question mailto:myvrml@263.net <淘宝热门商品：