ch08.htm

corba比较入门级的介绍详细间接了corba访问发布各种细节。

application class diagram.</I>
<H3><A NAME="Heading5"></A><FONT COLOR="#000077">Two New Exceptions: AuthorizationException
and InvalidATMException</FONT></H3>
<P>The operations in the <TT>ATM</TT> class suggest the need for a new exception.
To meet this need, define a new exception (call it <TT>AuthorizationException</TT>)
that can be thrown by any of the <TT>ATM</TT> methods. Later, you'll implement these
methods to raise an <TT>AuthorizationException</TT> if there is a problem authenticating
the customer (for example, the customer-supplied PIN doesn't match the <TT>pin</TT>
stored in the <TT>ATMCard</TT>) or authorizing the customer (for example, if the
<TT>Account</TT> passed to a method in <TT>ATM</TT> is not authorized on the given
<TT>ATMCard</TT>).</P>
<P>Also, recall the new methods added to the <TT>BankServer</TT> interface. Because
they essentially duplicate the <TT>Bank</TT>-related operations, which raise <TT>InvalidBankException</TT>s,
it follows that there ought to be an analogous exception for the <TT>ATM</TT>-related
operations. Therefore, you'll want to define the <TT>InvalidATMException</TT>, which
is used just as you might expect.
<H2><A NAME="Heading6"></A><FONT COLOR="#000077">Modifying the IDL Specification</FONT></H2>
<P>The modification of the IDL specifications is straightforward. Start with the
modified <TT>Bank</TT> interface, which appears in Listing 8.1 with changes highlighted
in<B> bold.</B>
<H4><FONT COLOR="#000077">Listing 8.1. Modified Bank.idl.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // Bank.idl</TT>
<TT> 2: </TT>
<TT> 3: // Forward declaration of Bank interface.</TT>
<TT> 4: interface Bank;</TT>
<TT> 5: </TT>
<TT> 6: #ifndef Bank_idl</TT>
<TT> 7: #define Bank_idl</TT>
<TT> 8: </TT>
<TT> 9: // sequence of Banks</TT>
<TT>10: typedef sequence&lt;Bank&gt; BankList;</TT>
<TT>11: </TT>
<TT>12: #include &quot;Customer.idl&quot;</TT>
<TT>13: #include &quot;Account.idl&quot;</TT>
<B><TT>14: #include &quot;ATMCard.idl&quot;</TT></B>
<TT>15: #include &quot;Exceptions.idl&quot;</TT>
<TT>16: </TT>
<TT>17: // A Bank provides access to Accounts. It can create an Account</TT>
<TT>18: // on behalf of a Customer, delete an Account, or list the current</TT>
<TT>19: // Accounts with the Bank.</TT>
<TT>20: interface Bank {</TT>
<TT>21: </TT>
<TT>22:     // This Bank's name.</TT>
<TT>23:     attribute string name;</TT>
<TT>24: </TT>
<TT>25:     // This Bank's address.</TT>
<TT>26:     attribute string address;</TT>
<TT>27: </TT>
<TT>28:     // Create an Account on behalf of the given Customer, with the</TT>
<TT>29:     // given account type (&quot;savings&quot; or &quot;checking&quot;, where case is</TT>
<TT>30:     // significant), and the given opening balance.</TT>
<TT>31:     Account createAccount(in Customer customer, in string</TT>
<TT>32:             accountType, in float openingBalance);</TT>
<TT>33: </TT>
<TT>34:     // Delete the given Account. If the Account is not with this</TT>
<TT>35:     // Bank, this operation does nothing.</TT>
<TT>36:     void deleteAccount(in Account account)</TT>
<TT>37:             raises (InvalidAccountException);</TT>
<TT>38: </TT>
<TT>39:     // List all Accounts with this Bank.</TT>
<TT>40:     AccountList getAccounts();</TT>
<TT>41: </TT>
<B><TT>42:</TT></B><TT>     <B>// Issue an ATMCard with the initial PIN and initially</B></TT>
<B><TT>43:</TT></B><TT>     <B>// authorized on the given Account. If the Account is not with</B></TT>
<B><TT>44:</TT></B><TT>     <B>// this Bank, this operation does nothing.</B></TT>
<B><TT>45:</TT></B><TT>     <B>ATMCard issueATMCard(in short pin, in Account account)</B></TT>
<B><TT>46:</TT></B><TT>             <B>raises (InvalidAccountException);</B></TT>
<B><TT>47:</TT></B><TT> <B>};</B></TT>
<TT>48: 
49: #endif</TT> </FONT></PRE>
<P>Turn your attention to the modified <TT>Exceptions.idl</TT>, which now contains
the newly created <TT>AuthorizationException</TT> and <TT>InvalidATMException</TT>.
The modified file appears in Listing 8.2.
<H4><FONT COLOR="#000077">Listing 8.2. Modified Exceptions.idl.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // Exceptions.idl</TT>
<TT> 2: </TT>
<TT> 3: #ifndef Exceptions_idl</TT>
<TT> 4: #define Exceptions_idl</TT>
<TT> 5: </TT>
<B><TT> 6: // This exception is thrown when an authorization fails; for</TT></B>
<B><TT> 7: // instance, if a Customer-entered PIN does not match the PIN for</TT></B>
<B><TT> 8: // the supplied ATMCard.</TT></B>
<B><TT> 9: exception AuthorizationException {</TT></B>
<B><TT>10:</TT></B><TT> </TT>
<B><TT>11: };</TT></B>
<TT>12: </TT>
<TT>13: // This exception is thrown when an invalid amount is passed to a</TT>
<TT>14: // method; for instance, if an account is asked to deposit a</TT>
<TT>15: // negative amount of funds.</TT>
<TT>16: exception InvalidAmountException {</TT>
<TT>17: </TT>
<TT>18: };</TT>
<TT>19: </TT>
<TT>20: // This exception is thrown when an invalid Account is passed to a</TT>
<TT>21: // method expecting an Account object.</TT>
<TT>22: exception InvalidAccountException {</TT>
<TT>23: </TT>
<TT>24: };</TT>
<TT>25: </TT>
<TT>26: // This exception is thrown when an invalid Bank is passed to a</TT>
<TT>27: // method expecting a Bank object.</TT>
<TT>28: exception InvalidBankException {</TT>
<TT>29: </TT>
<TT>30: };</TT>
<TT>31: </TT>
<B><TT>32: // This exception is thrown when an invalid ATM is passed to a</TT></B>
<B><TT>33: // method expecting an ATM object.</TT></B>
<B><TT>34: exception InvalidATMException {</TT></B>
<B><TT>35:</TT></B><TT> </TT>
<B><TT>36: };</TT></B>
<TT>37: </TT>
<TT>38: // This exception is thrown when there are insufficient funds to</TT>
<TT>39: // cover a transaction; for instance, if a withdrawal attempts to</TT>
<TT>40: // remove more funds than are available in an account.</TT>
<TT>41: exception InsufficientFundsException {</TT>
<TT>42: </TT>
<TT>43: };</TT>
<TT>44: 
45: #endif</TT></FONT> </PRE>
<P>Now consider the IDL mappings for the newly created classes <TT>ATM</TT> and <TT>ATMCard</TT>,
which appear in Listings 8.3 and 8.4. There are no surprises in the IDL interface
definitions; all member data and methods map to IDL as you might expect.
<H4><FONT COLOR="#000077">Listing 8.3. ATM.idl.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // ATM.idl</TT>
<TT> 2: </TT>
<TT> 3: // Forward declaration of ATM interface.</TT>
<TT> 4: interface ATM;</TT>
<TT> 5: </TT>
<TT> 6: #ifndef ATM_idl</TT>
<TT> 7: #define ATM_idl</TT>
<TT> 8: </TT>
<TT> 9: // sequence of ATMs</TT>
<TT>10: typedef sequence&lt;ATM&gt; ATMList;</TT>
<TT>11: </TT>
<TT>12: #include &quot;Account.idl&quot;</TT>
<TT>13: #include &quot;ATMCard.idl&quot;</TT>
<TT>14: #include &quot;Exceptions.idl&quot;</TT>
<TT>15: </TT>
<TT>16: // An ATM is used to (indirectly) access Accounts. Each operation</TT>
<TT>17: // through the ATM is verified through the ATMCard given; for</TT>
<TT>18: // example, an Account being operated on must be authorized by the</TT>
<TT>19: // given ATMCard.</TT>
<TT>20: interface ATM {</TT>
<TT>21: </TT>
<TT>22:     // This ATM's name.</TT>
<TT>23:     attribute string name;</TT>
<TT>24: </TT>
<TT>25:     // Withdraw the given amount from the given Account. Returns</TT>
<TT>26:     // the new account balance. If the given ATMCard is not</TT>
<TT>27:     // authorized on the given Account, or the given PIN does not</TT>
<TT>28:     // match the ATMCard's PIN, this operation does nothing.</TT>
<TT>29:     float withdraw(in ATMCard card, in Account account, in short</TT>
<TT>30:             pin, in float amount) raises (AuthorizationException,</TT>
<TT>31:             InvalidAmountException, InsufficientFundsException);</TT>
<TT>32: </TT>
<TT>33:     // Deposit the given amount into the given Account. Returns the</TT>
<TT>34:     // new account balance. If the given ATMCard is not authorized</TT>
<TT>35:     // on the given Account, or the given PIN does not match the</TT>
<TT>36:     // ATMCard's PIN, this operation does nothing.</TT>
<TT>37:     float deposit(in ATMCard card, in Account account, in short</TT>
<TT>38:             pin, in float amount) raises (AuthorizationException,</TT>
<TT>39:             InvalidAmountException);</TT>
<TT>40: </TT>
<TT>41:     // Return the current balance of the given Account. If the</TT>
<TT>42:     // given ATMCard is not authorized on the given Account, or the</TT>
<TT>43:     // given PIN does not match the ATMCard's PIN, this operation</TT>
<TT>44:     // does nothing.</TT>
<TT>45:     float getBalance(in ATMCard card, in Account account, in short</TT>
<TT>46:             pin) raises (AuthorizationException);</TT>
<TT>47: };</TT>
<TT>48: 
49: #endif</TT></FONT></PRE>
<H4><FONT COLOR="#000077">Listing 8.4. ATMCard.idl.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // ATMCard.idl</TT>
<TT> 2: </TT>
<TT> 3: // Forward declaration of ATMCard interface.</TT>
<TT> 4: interface ATMCard;</TT>
<TT> 5: </TT>
<TT> 6: #ifndef ATMCard_idl</TT>
<TT> 7: #define ATMCard_idl</TT>
<TT> 8: </TT>
<TT> 9: // sequence of ATMCards</TT>
<TT>10: typedef sequence&lt;ATMCard&gt; ATMCardList;</TT>
<TT>11: </TT>
<TT>12: #include &quot;Account.idl&quot;</TT>
<TT>13: #include &quot;Exceptions.idl&quot;</TT>
<TT>14: </TT>
<TT>15: // An ATMCard is used to access an ATM. It maintains a list of</TT>
<TT>16: // Accounts which it is authorized to access, as well as a PIN</TT>
<TT>17: // which must be provided when the ATMCard is used.</TT>
<TT>18: interface ATMCard {</TT>
<TT>19: </TT>
<TT>20:     // This ATMCard's PIN.</TT>
<TT>21:     attribute short pin;</TT>
<TT>22: </TT>
<TT>23:     // List all Accounts which this ATMCard is authorized to use.</TT>
<TT>24:     AccountList getAccounts();</TT>
<TT>25: </TT>
<TT>26:     // Add the given Account to the list of Accounts which this</TT>
<TT>27:     // ATMCard is authorized to use.</TT>
<TT>28:     void addAccount(in Account account)</TT>
<TT>29:             raises (InvalidAccountException);</TT>
<TT>30: </TT>
<TT>31:     // Remove the given Account from the list of Accounts which</TT>
<TT>32:     // this ATMCard is authorized to use.</TT>
<TT>33:     void removeAccount(in Account account)</TT>
<TT>34:             raises (InvalidAccountException);</TT>
<TT>35: </TT>
<TT>36:     // Return true if the given Account is authorized on this</TT>
<TT>37:     // ATMCard.</TT>
<TT>38:     boolean isAuthorized(in Account account);</TT>
<TT>39: };</TT>
<TT>40: 
41: #endif</TT> </FONT></PRE>
<P>This concludes the analysis and design portion of the ATM functionality enhancements;
you're now ready to begin implementing the changes in the code itself.
<H2><A NAME="Heading7"></A><FONT COLOR="#000077">Implementing the New Functionality</FONT></H2>
<P>To implement the <TT>ATM</TT>-related enhancements, you must modify the implementation
files to provide the new functionality. As a quick overview, the changes you need
to make are as follows:

<UL>
	<LI><I>Enhance the </I><TT>BankServer</TT><I>.</I> Essentially, everything that the
	<TT>BankServer</TT> currently does for <TT>Bank</TT>s, you will extend it to do for
	<TT>ATM</TT>s as well.<BR>
	<BR>
	
	<LI><I>Enhance the </I><TT>Bank</TT><I>.</I> In addition to requiring the capability
	to issue <TT>ATMCards</TT>, the <TT>Bank</TT> also provides the implementation for
	the <TT>ATMCard</TT> as well.<BR>
	<BR>
	
	<LI><I>Implement the </I><TT>ATM</TT><I> server.</I> Essentially, the <TT>ATM</TT>
	accepts transaction requests from <TT>Customer</TT>s, validates the <TT>Customer</TT>'s
	authorization against an <TT>ATMCard</TT>, and, if authorized, forwards the requests
	to the appropriate <TT>Account</TT>s.<BR>
	<BR>
	
	<LI><I>Implement the </I><TT>ATM</TT><I> client.</I> This application is an extension
	of the previous <TT>Bank</TT> client, modified to create an <TT>Account</TT> and
	subsequently access that <TT>Account</TT> through an <TT>ATM</TT> rather than directly.
</UL>

<H3><A NAME="Heading8"></A><FONT COLOR="#000077">Enhancing the BankServer</FONT></H3>
<P>The first step in the implementation of ATM functionality is to enhance the <TT>BankServer</TT>
to support <TT>ATM</TT>s as well as <TT>Bank</TT>s. Because the support is exactly
the same for each type of object (for example, <TT>ATM</TT>s and <TT>Bank</TT>s can
both register and unregister with the <TT>BankServer</TT>), the <TT>ATM</TT>-related
methods can be copied almost directly from their <TT>Bank</TT>-related counterparts.
The necessary modifications to the <TT>BankServer</TT> implementation files appear
in Listings 8.5-8.7, with changes from the previous version highlighted in <B>bold.</B>
<H4><FONT COLOR="#000077">Listing 8.5. BankServerImpl.h.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // BankServerImpl.h</TT>
<TT> 2: </TT>
<TT> 3: #ifndef BankServerImpl_h</TT>
<TT> 4: #define BankServerImpl_h</TT>
<TT> 5: </TT>
<TT> 6: #include &lt;vector&gt;</TT>
<TT> 7: </TT>
<TT> 8: #include &quot;../BankServer_s.h&quot;</TT>
<TT> 9: </TT>
<TT>10: class BankServerImpl : public _sk_BankServer {</TT>
<TT>11: </TT>
<TT>12: public:</TT>
<TT>13: </TT>
<TT>14:     // Constructor.</TT>
<TT>15:     BankServerImpl(const char* name);</TT>
<TT>16: </TT>
<TT>17:     // Destructor.</TT>
<TT>18:     ~BankServerImpl();</TT>
<TT>19: </TT>
<TT>20:     // These methods are described in BankServer.idl.</TT>
<TT>21:     virtual void registerBank(Bank_ptr bank) throw</TT>
<TT>22:             (InvalidBankException);</TT>
<TT>23:     virtual void unregisterBank(Bank_ptr bank) throw</TT>
<TT>24:             (InvalidBankException);</TT>
<TT>25:     virtual BankList* getBanks();</TT>
<B><TT>26:     virtual void registerATM(ATM_ptr atm) throw</TT></B>
<B><TT>27:             (InvalidATMException);</TT></B>
<B><TT>28:     virtual void unregisterATM(ATM_ptr atm) throw</TT></B>
<B><TT>29:             (InvalidATMException);</TT></B>
<B><TT>30:     virtual ATMList* getATMs();</TT></B>
<TT>31: </TT>
<TT>32: private:</TT>
<TT>33: </TT>
<TT>34:     // Default constructor.</TT>