ch09.htm

corba比较入门级的介绍详细间接了corba访问发布各种细节。

new <TT>requestUpdateService()</TT> method. Also, notice that the <TT>InvalidAccountException</TT>
comes into play again here, in case an <TT>Account</TT> is passed that does not belong
to the <TT>Bank</TT>.</P>
<P>The other changes are made to <TT>Customer.idl</TT>, which appears in Listing
9.2.
<H4><FONT COLOR="#000077">Listing 9.2. Modified Customer.idl.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // Customer.idl</TT>
<TT> 2: </TT>
<TT> 3: // Forward declaration of Customer interface.</TT>
<TT> 4: interface Customer;</TT>
<TT> 5: </TT>
<TT> 6: #ifndef Customer_idl</TT>
<TT> 7: #define Customer_idl</TT>
<TT> 8: </TT>
<TT> 9: // sequence of Customers</TT>
<TT>10: typedef sequence&lt;Customer&gt; CustomerList;</TT>
<TT>11: </TT>
<TT>12: #include &quot;Account.idl&quot;</TT>
<TT>13: </TT>
<TT>14: // A Customer can hold one or more Accounts. Presumably, the</TT>
<TT>15: // Customer is what drives the rest of this application.</TT>
<TT>16: interface Customer {</TT>
<TT>17: </TT>
<TT>18:     // This Customer's name.</TT>
<TT>19:     attribute string name;</TT>
<TT>20: </TT>
<TT>21:     // This Customer's Social Security number.</TT>
<TT>22:     readonly attribute string socialSecurityNumber;</TT>
<TT>23: </TT>
<TT>24:     // This Customer's address.</TT>
<TT>25:     attribute string address;</TT>
<TT>26: </TT>
<TT>27:     // This Customer's mother's maiden name.</TT>
<TT>28:     readonly attribute string mothersMaidenName;</TT>
<TT>29: </TT>
<TT>30:     // Return a list of Accounts held (or co-held) by this</TT>
<TT>31:     // Customer.</TT>
<TT>32:     AccountList getAccounts();</TT>
<TT>33: </TT>
<B><TT>34:     // Send an update message to this Customer regarding the given</TT></B>
<B><TT>35:     // Account and its new balance.</TT></B>
<B><TT>36:     oneway void updateAccountBalance(in Account account, in float</TT></B>
<B><TT>37:             balance);</TT></B>
<TT>38: };</TT>
<TT>39: 
40: #endif</TT> </FONT></PRE>
<P>Again, changes to <TT>Customer.idl</TT> are minimal, adding only the <TT>updateAccountBalance()</TT>
method. Note the use of the <TT>oneway</TT> modifier, indicating that when this method
is called, it will return to the caller immediately.</P>
<P>You're now ready to proceed with the changes to the implementation itself.
<H2><A NAME="Heading5"></A><FONT COLOR="#000077">Implementing the New Functionality</FONT></H2>
<P>Implementing the account update functionality is also a simple process. Given
that only two methods have been added to the entire system, there are only a couple
of steps involved:

<UL>
	<LI>Implement <TT>requestUpdateService()</TT> in the <TT>BankImpl</TT> class. The
	<TT>BankImpl</TT> must keep track of all <TT>Account</TT>s for which the service
	is activated; when it comes time to send update messages to the <TT>Account</TT>s'
	<TT>Customer</TT>s, the <TT>BankImpl</TT> can simply traverse this list of <TT>Account</TT>s.<BR>
	<BR>
	
	<LI>Implement <TT>updateAccountBalance()</TT> in the <TT>CustomerImpl</TT> class.
	This method can be as trivial as simply printing a message indicating the <TT>Account</TT>
	and its new balance.
</UL>

<H3><A NAME="Heading6"></A><FONT COLOR="#000077">Enhancing the BankImpl</FONT></H3>
<P>First, you'll modify <TT>BankImpl</TT> to provide the <TT>requestUpdateService()</TT>
functionality. As already mentioned, the <TT>BankImpl</TT> must maintain a list of
<TT>Account</TT>s for which the automatic update service is activated. You'll see
how this is done in Listing 9.3, <TT>BankImpl.h</TT>, with changes highlighted in<B>
bold.</B>
<H4><FONT COLOR="#000077">Listing 9.3. BankImpl.h.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT> 1: // BankImpl.h</TT>
<TT> 2: </TT>
<TT> 3: #ifndef BankImpl_h</TT>
<TT> 4: #define BankImpl_h</TT>
<TT> 5: </TT>
<TT> 6: #include &lt;vector&gt;</TT>
<TT> 7: </TT>
<TT> 8: #include &quot;../Bank_s.h&quot;</TT>
<TT> 9: </TT>
<TT>10: class BankImpl : public _sk_Bank {</TT>
<TT>11: </TT>
<TT>12: public:</TT>
<TT>13: </TT>
<TT>14:     // Constructor.</TT>
<TT>15:     //</TT>
<TT>16:     // name - This Bank's name.</TT>
<TT>17:     BankImpl(const char* name);</TT>
<TT>18: </TT>
<TT>19:     // Destructor.</TT>
<TT>20:     ~BankImpl();</TT>
<TT>21: </TT>
<TT>22:     // These methods are described in Bank.idl.</TT>
<TT>23:     virtual char* name();</TT>
<TT>24:     virtual void name(const char* val);</TT>
<TT>25:     virtual char* address();</TT>
<TT>26:     virtual void address(const char* val);</TT>
<TT>27:     virtual Account_ptr createAccount(Customer_ptr customer,</TT>
<TT>28:             const char* accountType, CORBA::Float openingBalance);</TT>
<TT>29:     virtual void deleteAccount(Account_ptr account) throw</TT>
<TT>30:             (InvalidAccountException);</TT>
<TT>31:     virtual AccountList* getAccounts();</TT>
<TT>32:     virtual ATMCard_ptr issueATMCard(CORBA::Short pin, Account_ptr</TT>
<TT>33:             account) throw (InvalidAccountException);</TT>
<B><TT>34:     virtual void requestUpdateService(Account_ptr account) throw</TT></B>
<B><TT>35:             (InvalidAccountException);</TT></B>
<TT>36: </TT>
<TT>37: protected:</TT>
<TT>38: </TT>
<TT>39:     // Return the next available account number. The result is</TT>
<TT>40:     // returned in a static buffer.</TT>
<TT>41:     char* getNextAccountNumber();</TT>
<TT>42: </TT>
<TT>43:     // Return the current date in the form &quot;Mmm DD YYYY&quot;. The result</TT>
<TT>44:     // is returned in a static buffer.</TT>
<TT>45:     char* getCurrentDate();</TT>
<TT>46: </TT>
<TT>47: private:</TT>
<TT>48: </TT>
<TT>49:     // Default constructor.</TT>
<TT>50:     BankImpl();</TT>
<TT>51: </TT>
<TT>52:     // This Bank's name.</TT>
<TT>53:     char* myName;</TT>
<TT>54: </TT>
<TT>55:     // This Bank's address.</TT>
<TT>56:     char* myAddress;</TT>
<TT>57: </TT>
<TT>58:     // This Bank's Accounts.</TT>
<TT>59:     std::vector&lt;Account_ptr&gt; myAccounts;</TT>
<TT>60: </TT>
<B><TT>61:     // The Accounts which are subscribed to the automatic update</TT></B>
<B><TT>62:     // service.</TT></B>
<B><TT>63:     std::vector&lt;Account_ptr&gt; mySubscribedAccounts;</TT></B>
<TT>64: </TT>
<TT>65:     // The next available account number.</TT>
<TT>66:     unsigned int myNextAccountNumber;</TT>
<TT>67: };</TT>
<TT>68: 
69: #endif</TT> </FONT></PRE>
<P>In <TT>BankImpl.h</TT>, note the addition of the <TT>requestUpdateService()</TT>
method and the <TT>mySubscribedAccounts</TT> data member. <TT>mySubscribedAccounts</TT>
is a C++ Standard Template Library <TT>vector</TT>, just like the <TT>myAccounts</TT>
member, which contains all the <TT>Account</TT>s held by a particular <TT>Bank</TT>.
In Listing 9.4,<TT> BankImpl.cpp</TT>, you'll observe how the elements of <TT>mySubscribedAccounts</TT>
are managed.
<H4><FONT COLOR="#000077">Listing 9.4. BankImpl.cpp.</FONT></H4>
<PRE><FONT COLOR="#0066FF"><TT>  1: // BankImpl.cpp</TT>
<TT>  2: </TT>
<TT>  3: #include &quot;BankImpl.h&quot;</TT>
<TT>  4: </TT>
<B><TT>  5: #include &lt;process.h&gt;</TT></B>
<TT>  6: </TT>
<TT>  7: #include &lt;time.h&gt;</TT>
<TT>  8: #include &lt;string.h&gt;</TT>
<TT>  9: #include &lt;iostream.h&gt;</TT>
<TT> 10: #include &lt;algorithm&gt;</TT>
<TT> 11: #include &lt;functional&gt;</TT>
<TT> 12: </TT>
<TT> 13: #include &quot;SavingsAccountImpl.h&quot;</TT>
<TT> 14: #include &quot;CheckingAccountImpl.h&quot;</TT>
<TT> 15: #include &quot;ATMCardImpl.h&quot;</TT>
<TT> 16: </TT>
<TT> 17: extern CORBA::BOA_var boa;</TT>
<TT> 18: </TT>
<TT> 19: // STL-derived unary function which returns TRUE if Accounts are</TT>
<TT> 20: // equal.</TT>
<TT> 21: class IsAccountEqual : public std::unary_function&lt;Account_ptr,</TT>
<TT> 22:         bool&gt; {</TT>
<TT> 23: public:</TT>
<TT> 24:     IsAccountEqual(argument_type account) { myAccount = account; }</TT>
<TT> 25:     result_type operator()(argument_type account) { return account-&gt;</TT>
<TT> 26:             _is_equivalent(myAccount) != 0; }</TT>
<TT> 27: private:</TT>
<TT> 28:     argument_type myAccount;</TT>
<TT> 29: };</TT>
<TT> 30: </TT>
<B><TT> 31: void updateAccountThreadFunction(LPVOID pParam) {</TT></B>
<B><TT> 32: </TT></B>
<B><TT> 33:     std::vector&lt;Account_ptr&gt;* accounts = (std::</TT></B>
<B><TT> 34:             vector&lt;Account_ptr&gt;*)pParam;</TT></B>
<B><TT> 35: </TT></B>
<B><TT> 36:     while (1) {</TT></B>
<B><TT> 37:         Sleep(60000);</TT></B>
<B><TT> 38:         cout &lt;&lt; &quot;BankImpl: Updating Accounts.&quot; &lt;&lt; endl;</TT></B>
<B><TT> 39: </TT></B>
<B><TT> 40:         // Iterate through the list of Accounts.</TT></B>
<B><TT> 41:         for (int i = 0; i &lt; accounts-&gt;size(); i++) {</TT></B>
<B><TT> 42: </TT></B>
<B><TT> 43:             // For each Account, get the list of Customers and send</TT></B>
<B><TT> 44:             // an update message to each.</TT></B>
<B><TT> 45:             CustomerList* customers = (*accounts)[i]-&gt;</TT></B>
<B><TT> 46:                     getCustomers();</TT></B>
<B><TT> 47:             for (CORBA::Long j = 0; j &lt; customers-&gt;length(); j++) {</TT></B>
<B><TT> 48:                 try {</TT></B>
<B><TT> 49:                     (*customers)[i]-&gt;</TT></B>
<B><TT> 50:                             updateAccountBalance((*accounts)[i],</TT></B>
<B><TT> 51:                             (*accounts)[i]-&gt;balance());</TT></B>
<B><TT> 52:                 } catch (const CORBA::Exception&amp;) {</TT></B>
<B><TT> 53: </TT></B>
<B><TT> 54:                     // Ignore the exception; we don't care if</TT></B>
<B><TT> 55:                     // there's a problem with the update.</TT></B>
<B><TT> 56:                 }</TT></B>
<B><TT> 57:             }</TT></B>
<B><TT> 58:         }</TT></B>
<B><TT> 59:     }</TT></B>
<B><TT> 60: }</TT></B>
<TT> 61: </TT>
<TT> 62: // Constructor.</TT>
<TT> 63: //</TT>
<TT> 64: // name - This Bank's name.</TT>
<TT> 65: BankImpl::BankImpl(const char* name) : _sk_Bank(name), myAccounts(),</TT>
<TT> 66:         <B>mySubscribedAccounts(),</B> myName(strdup(name)),</TT>
<TT> 67:         myAddress(strdup(&quot;123 Elm Street, Anywhere USA 12345&quot;)),</TT>
<TT> 68:         myNextAccountNumber(0) {</TT>
<TT> 69: </TT>
<B><TT> 70:     _beginthread(&amp;updateAccountThreadFunction, 0,</TT></B>
<B><TT> 71:             &amp;mySubscribedAccounts);</TT></B>
<TT> 72: }</TT>
<TT> 73: </TT>
<TT> 74: // Default constructor.</TT>
<TT> 75: BankImpl::BankImpl() : myAccounts(), <B>mySubscribedAccounts(),</B></TT>
<TT> 76:         myName(NULL), myAddress(NULL), myNextAccountNumber(0) {</TT>
<TT> 77: </TT>
<TT> 78: }</TT>
<TT> 79: </TT>
<TT> 80: // Destructor.</TT>
<TT> 81: BankImpl::~BankImpl() {</TT>
<TT> 82: </TT>
<TT> 83:     cout &lt;&lt; &quot;Bank \&quot;&quot; &lt;&lt; name() &lt;&lt; &quot;\&quot; being destroyed.&quot; &lt;&lt; endl;</TT>
<TT> 84:     free(myName);</TT>
<TT> 85:     free(myAddress);</TT>
<TT> 86: }</TT>
<TT> 87: </TT>
<TT> 88: char* BankImpl::name() {</TT>
<TT> 89: </TT>
<TT> 90:     return CORBA::strdup(myName);</TT>
<TT> 91: }</TT>
<TT> 92: </TT>
<TT> 93: void BankImpl::name(const char* val) {</TT>
<TT> 94: </TT>
<TT> 95:     free(myName);</TT>
<TT> 96:     myName = strdup(val);</TT>
<TT> 97: }</TT>
<TT> 98: </TT>
<TT> 99: char* BankImpl::address() {</TT>
<TT>100: </TT>
<TT>101:     return CORBA::strdup(myAddress);</TT>
<TT>102: }</TT>
<TT>103: </TT>
<TT>104: void BankImpl::address(const char* val) {</TT>
<TT>105: </TT>
<TT>106:     free(myAddress);</TT>
<TT>107:     myAddress = strdup(val);</TT>
<TT>108: }</TT>
<TT>109: </TT>
<TT>110: Account_ptr BankImpl::createAccount(Customer_ptr customer,</TT>
<TT>111:         const char* accountType, CORBA::Float openingBalance) {</TT>
<TT>112: </TT>