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}<a name="wp80135"> </a>
</pre></div>
<a name="wp80136"> </a><h3 class="pHeading2">
Dropping a Player from a Team
</h3>
<a name="wp80137"> </a><h4 class="pHeading3">
1. RosterClient
</h4>
<a name="wp80138"> </a><p class="pBody">
To drop player <code class="cCode">P2</code> from team <code class="cCode">T1</code>, the client would call the <code class="cCode">dropPlayer</code> method of the <code class="cCode">RosterEJB</code> session bean:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
myRoster.dropPlayer(&quot;P2&quot;, &quot;T1&quot;);<a name="wp80139"> </a>
</pre></div>
<a name="wp80140"> </a><h4 class="pHeading3">
2. RosterEJB
</h4>
<a name="wp80141"> </a><p class="pBody">
The <code class="cCode">dropPlayer</code> method retrieves the <code class="cCode">PlayerEJB</code> and <code class="cCode">TeamEJB</code> instances by calling their <code class="cCode">findByPrimaryKey</code> methods. Next, it invokes the <code class="cCode">dropPlayer</code> business method of the <code class="cCode">TeamEJB</code> entity bean. The <code class="cCode">dropPlayer</code> method of the <code class="cCode">RosterEJB</code> session bean follows:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public void dropPlayer(String playerId, String teamId) {

&nbsp;&nbsp;try {
&nbsp;&nbsp;&nbsp;&nbsp;LocalPlayer player =
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;playerHome.findByPrimaryKey(playerId);
&nbsp;&nbsp;&nbsp;&nbsp;LocalTeam team = teamHome.findByPrimaryKey(teamId);
&nbsp;&nbsp;&nbsp;&nbsp;team.dropPlayer(player);
&nbsp;&nbsp;} catch (Exception ex) {
&nbsp;&nbsp;&nbsp;&nbsp;throw new EJBException(ex.getMessage());
&nbsp;&nbsp;}
}<a name="wp80142"> </a>
</pre></div>
<a name="wp80143"> </a><h4 class="pHeading3">
3. TeamEJB
</h4>
<a name="wp80144"> </a><p class="pBody">
The <code class="cCode">dropPlayer</code> method updates the <code class="cCode">TeamEJB-PlayerEJB</code> relationship. First, the method retrieves the <code class="cCode">Collection</code> of <code class="cCode">LocalPlayer</code> objects that correspond to the <code class="cCode">players</code> relationship field. Next, it drops the target <code class="cCode">player</code> by calling the <code class="cCode">remove</code> method of the <code class="cCode">Collection</code> interface. Here is the <code class="cCode">dropPlayer</code> method of the <code class="cCode">TeamEJB</code> entity bean:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public void dropPlayer(LocalPlayer player) {

&nbsp;&nbsp;try {
&nbsp;&nbsp;&nbsp;&nbsp;Collection players = getPlayers();
&nbsp;&nbsp;&nbsp;&nbsp;players.remove(player);
&nbsp;&nbsp;} catch (Exception ex) {
&nbsp;&nbsp;&nbsp;&nbsp;throw new EJBException(ex.getMessage());
&nbsp;&nbsp;}
}<a name="wp80145"> </a>
</pre></div>
<a name="wp80146"> </a><h3 class="pHeading2">
Getting the Players of a Team
</h3>
<a name="wp80147"> </a><h4 class="pHeading3">
1. RosterClient
</h4>
<a name="wp80148"> </a><p class="pBody">
The client can fetch a team's players by calling the <code class="cCode">getPlayersOfTeam</code> method of the <code class="cCode">RosterEJB</code> session bean. This method returns an <code class="cCode">ArrayList</code> of <code class="cCode">PlayerDetails</code> objects. A <code class="cCode">PlayerDetail</code> object contains four variables--<code class="cCode">playerId</code>, <code class="cCode">name</code>, <code class="cCode">position</code>, and <code class="cCode">salary</code>--which are copies of the <code class="cCode">PlayerEJB</code> persistent fields. The <code class="cCode">RosterClient</code> calls the <code class="cCode">getPlayersOfTeam</code> method as follows:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
playerList = myRoster.getPlayersOfTeam(&quot;T2&quot;);<a name="wp80149"> </a>
</pre></div>
<a name="wp80150"> </a><h4 class="pHeading3">
2. RosterEJB
</h4>
<a name="wp80151"> </a><p class="pBody">
The <code class="cCode">getPlayersOfTeam</code> method of the <code class="cCode">RosterEJB</code> session bean locates the <code class="cCode">LocalTeam</code> object of the target team by invoking the <code class="cCode">findByPrimaryKey</code> method. Next, the <code class="cCode">getPlayersOfTeam</code> method calls the <code class="cCode">getPlayers</code> method of the <code class="cCode">TeamEJB</code> entity bean. Here is the source code for the <code class="cCode">getPlayersOfTeam</code> method:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public ArrayList getPlayersOfTeam(String teamId) { 

&nbsp;&nbsp;Collection players = null;

&nbsp;&nbsp;try {
&nbsp;&nbsp;&nbsp;&nbsp;LocalTeam team = teamHome.findByPrimaryKey(teamId);
&nbsp;&nbsp;&nbsp;&nbsp;players = team.getPlayers();
&nbsp;&nbsp;} catch (Exception ex) {
&nbsp;&nbsp;&nbsp;&nbsp;throw new EJBException(ex.getMessage());
&nbsp;&nbsp;}

&nbsp;&nbsp;return copyPlayersToDetails(players);
}<a name="wp80153"> </a>
</pre></div>
<a name="wp80154"> </a><p class="pBody">
The <code class="cCode">getPlayersOfTeam</code> method returns the <code class="cCode">ArrayList</code> of <code class="cCode">PlayerDetails</code> objects that is generated by the <code class="cCode">copyPlayersToDetails</code> method:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
private ArrayList copyPlayersToDetails(Collection players) {

&nbsp;&nbsp;ArrayList detailsList = new ArrayList();
&nbsp;&nbsp;Iterator i = players.iterator();

&nbsp;&nbsp;while (i.hasNext()) {
&nbsp;&nbsp;&nbsp;&nbsp;LocalPlayer player = (LocalPlayer) i.next();
&nbsp;&nbsp;&nbsp;&nbsp;PlayerDetails details = 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;new PlayerDetails(player.getPlayerId(),
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;player.getName(), player.getPosition(),
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;player.getSalary());
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;detailsList.add(details);
&nbsp;&nbsp;}

&nbsp;&nbsp;return detailsList;
} <a name="wp80155"> </a>
</pre></div>
<a name="wp80156"> </a><h4 class="pHeading3">
3. TeamEJB
</h4>
<a name="wp80157"> </a><p class="pBody">
The <code class="cCode">getPlayers</code> method of the <code class="cCode">TeamEJB</code> entity bean is an access method of the <code class="cCode">players</code> relationship field:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public abstract Collection getPlayers();<a name="wp80158"> </a>
</pre></div>
<a name="wp80159"> </a><p class="pBody">
This method is exposed to local clients because it is defined in the local interface, <code class="cCode">LocalTeam</code>:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public Collection getPlayers();<a name="wp80160"> </a>
</pre></div>
<a name="wp80161"> </a><p class="pBody">
When invoked by a local client, a <code class="cCode">get</code> access method returns a reference to the relationship field. If the local client alters the object returned by a <code class="cCode">get</code> access method, it also alters the value of the relationship field inside the entity bean. For example, a local client of the <code class="cCode">TeamEJB</code> entity bean could drop a player from a team as follows:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
LocalTeam team = teamHome.findByPrimaryKey(teamId);
Collection players = team.getPlayers();
players.remove(player);<a name="wp80162"> </a>
</pre></div>
<a name="wp80164"> </a><p class="pBody">
If you want to prevent a local client from modifying a relationship field in this manner, you should take the approach described in the next section.
</p>
<a name="wp80165"> </a><h3 class="pHeading2">
Getting a Copy of a Team's Players
</h3>
<a name="wp80166"> </a><p class="pBody">
In contrast to the methods discussed in the preceding section, the methods in this section demonstrate the following techniques:
</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp80167"> </a><div class="pSmartList1"><li>Filtering the information passed back to the remote client</li></div>
<a name="wp80168"> </a><div class="pSmartList1"><li>Preventing the local client from directly modifying a relationship field</li></div>
</ul></div>
<a name="wp80169"> </a><h4 class="pHeading3">
1. RosterClient
</h4>
<a name="wp80170"> </a><p class="pBody">
If you wanted to hide the salary of a player from a remote client, you would require the client to call the <code class="cCode">getPlayersOfTeamCopy</code> method of the <code class="cCode">RosterEJB</code> session bean. Like the <code class="cCode">getPlayersOfTeam</code> method, the <code class="cCode">getPlayersOfTeamCopy</code> method returns an <code class="cCode">ArrayList</code> of <code class="cCode">PlayerDetails</code> objects. However, the objects returned by <code class="cCode">getPlayersOfTeamCopy</code> are different--their <code class="cCode">salary</code> variables have been set to zero. The <code class="cCode">RosterClient</code> calls the <code class="cCode">getPlayersOfTeamCopy</code> method as follows:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
playerList = myRoster.getPlayersOfTeamCopy(&quot;T5&quot;);<a name="wp80171"> </a>
</pre></div>
<a name="wp80172"> </a><h4 class="pHeading3">
2. RosterEJB
</h4>
<a name="wp80173"> </a><p class="pBody">
Unlike the <code class="cCode">getPlayersOfTeam</code> method, the <code class="cCode">getPlayersOfTeamCopy</code> method does not invoke the <code class="cCode">getPlayers</code> access method that is exposed in the <code class="cCode">LocalTeam</code> interface. Instead, the <code class="cCode">getPlayersOfTeamCopy</code> method retrieves a copy of the player information by invoking the <code class="cCode">getCopyOfPlayers</code> business method that is defined in the <code class="cCode">LocalTeam</code> interface. As a result, the <code class="cCode">getPlayersOfTeamCopy</code> method cannot modify the <code class="cCode">players</code> relationship field of <code class="cCode">TeamEJB</code>. Here is the source code for the <code class="cCode">getPlayersOfTeamCopy</code> method of <code class="cCode">RosterEJB</code>:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public ArrayList getPlayersOfTeamCopy(String teamId) { 

&nbsp;&nbsp;ArrayList playersList = null;

&nbsp;&nbsp;try {
&nbsp;&nbsp;&nbsp;&nbsp;LocalTeam team = teamHome.findByPrimaryKey(teamId);
&nbsp;&nbsp;&nbsp;&nbsp;playersList = team.getCopyOfPlayers();
&nbsp;&nbsp;} catch (Exception ex) {
&nbsp;&nbsp;&nbsp;&nbsp;throw new EJBException(ex.getMessage());
&nbsp;&nbsp;}

&nbsp;&nbsp;return playersList;
}<a name="wp80174"> </a>
</pre></div>
<a name="wp80175"> </a><h4 class="pHeading3">
3. TeamEJB
</h4>
<a name="wp80176"> </a><p class="pBody">
The <code class="cCode">getCopyOfPlayers</code> method of <code class="cCode">TeamEJB</code> returns an <code class="cCode">ArrayList</code> of <code class="cCode">PlayerDetails</code> objects. To create this <code class="cCode">ArrayList</code>, the method iterates through the <code class="cCode">Collection</code> of related <code class="cCode">LocalPlayer</code> objects and copies information to the variables of the <code class="cCode">PlayerDetails</code> objects. The method copies the values of <code class="cCode">PlayerEJB</code> persistent fields--except for the <code class="cCode">salary</code> field, which it sets to zero. As a result, a player's salary is hidden from a client that invokes the <code class="cCode">getPlayersOfTeamCopy</code> method. The source code for the <code class="cCode">getCopyOfPlayers</code> method of <code class="cCode">TeamEJB</code> follows.
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
public ArrayList getCopyOfPlayers() {

&nbsp;&nbsp;ArrayList playerList = new ArrayList();
&nbsp;&nbsp;Collection players = getPlayers();