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| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
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| <div class="breadcrumb"><a class="nav" href="s7.html" rel="section">§7 Role Encapsulation</a></div> |
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| <h2 class="sect">§7.1 Opaque roles<a class="img" href="s7.1.html" |
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| <p>The purpose of the two <code>IConfined</code> interfaces (see <a href="s6.2.a.html" |
| title="§6.2.(a) Interfaces for role encapsulation" |
| class="sect">§6.2.(a)</a>) is to define |
| <strong>opaque roles</strong>: Any role implementing <code>IConfined</code> |
| can be externalized using this type, such that external clients |
| cannot access any features of the role. The type <code>IConfined</code> |
| exposes no features and references of this type cannot be widened |
| to any type not even to <code>java.lang.Object</code>. |
| <br /> |
| If the actual role type is furthermore invisible outside the team |
| (by not declaring it <code>public</code>), it is perfectly safe to externalize |
| such roles using type <code>IConfined</code> (which is a public interface) |
| and pass them back to the owning team. The encapsulation |
| of the team is in no way breached by externalizing opaque roles, |
| which can only be used as a handle into internal state of the team. |
| |
| </p> |
| <p>The difference between the two mentioned interfaces is that |
| <code>ITeam.IConfined</code> requires to use this type or any subtype |
| as externalized role. Such a reference contains the information of |
| the enclosing team. Even stricter control can be imposed using the |
| regular interface <code>IConfined</code>. Here not even team membership |
| is visible to clients using a reference of this type. |
| |
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| width="88" /></a><address>© Stephan Herrmann, Christine Hundt, Marco Mosconi</address> |
| OT/J version 1.3 — last modified: 2010-05-18 |
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