关于EJB返回值的解决方案

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

> return v.elements();

> } catch (SQLException sqe) {

> log("SQLException: " + sqe);

> throw new EJBException (sqe);

> } finally {

> cleanup(con, ps);

> }

> }

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/

下面：

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：

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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

}

// 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