|
|
|
|
|
|
Comprehensive Example
Transaction integrity, message communication, and resource access are the major requirements of an Online-Transaction-Processing (OLTP) application.
This section provides a code sample that illustrates the ATMI transaction, buffer management, and communication routines operating together with SQL statements that access a resource manager. The example is borrowed from the ACCT server that is part of the BEA Tuxedo banking application (bankapp) and illustrates the CLOSE_ACCT service.
The example shows how the set transaction statement (line 49) is used to set the consistency level and access mode of the transaction before the first SQL statement that accesses the database. (When read/write access is specified, the consistency level defaults to high consistency.) The SQL query determines the amount to be withdrawn in order to close the account based on the value of the ACCOUNT_ID (lines 50-58).
tpalloc() allocates a buffer for the request message to the WITHDRAWAL service, and the ACCOUNT_ID and the amount to be withdrawn are placed in the buffer (lines 62-74). Next, a request is sent to the WITHDRAWAL service via a tpcall() call (line 79). An SQL delete statement then updates the database by removing the account in question (line 86).
If all is successful, the buffer allocated in the service is freed (line 98) and the TPSVCINFO data buffer that was sent to the service is updated to indicate the successful completion of the transaction (line 99). Then, if the service was the initiator, the transaction is automatically committed. tpreturn() returns TPSUCCESS, along with the updated buffer, to the client process that requested the closing of the account. Finally, the successful completion of the requested service is reported on the status line of the form.
After each function call, success or failure is determined. If a failure occurs, the buffer allocated in the service is freed, any transaction begun in the service is aborted, and the TPSVCINFO buffer is updated to show the cause of failure (lines 80-83). Finally, tpreturn() returns TPFAIL and the message in the updated buffer is reported on the status line of the form.
Note: When specifying the consistency level of a global transaction in a service routine, take care to define the level in the same way for all service routines that may participate in the same transaction.
ACCT Server
001 #include <stdio.h> /* UNIX */
002 #include <string.h> /* UNIX */
003 #include <fml.h> /* BEA Tuxedo System */
004 #include <atmi.h> /* BEA Tuxedo System */
005 #include <Usysflds.h> /* BEA Tuxedo System */
006 #include <sqlcode.h> /* BEA Tuxedo System */
007 #include <userlog.h> /* BEA Tuxedo System */
008 #include "bank.h" /* BANKING #defines */
009 #include "bank.flds.h" /* bankdb fields */
010 #include "event.flds.h" /* event fields */
011
012
013 EXEC SQL begin declare section;
014 static long account_id; /* account id */
015 static long branch_id; /* branch id */
016 static float bal, tlr_bal; /* BALANCE */
017 static char acct_type; /* account type*/
018 static char last_name[20], first_name[20]; /* last name, first name */
019 static char mid_init; /* middle initial */
020 static char address[60]; /* address */
021 static char phone[14]; /* telephone */
022 static long last_acct; /* last account branch gave */
023 EXEC SQL end declare section;
024 static FBFR *reqfb; /* fielded buffer for request message */
025 static long reqlen; /* length of request buffer */
026 static char amts[BALSTR]; /* string representation of float */
027 code for OPEN_ACCT service
028 /*
029 * Service to close an account
030 */
031 void
032 #ifdef __STDC__
033 LOSE_ACCT(TPSVCINFO *transb)
034 #else
035 CLOSE_ACCT(transb)
036 TPSVCINFO *transb;
037 #endif
038 {
039 FBFR *transf; /* fielded buffer of decoded message */
040 /* set pointer to TPSVCINFO data buffer */
041 transf = (FBFR *)transb->data;
042 /* must have valid account number */
043 if (((account_id = Fvall(transf, ACCOUNT_ID, 0)) < MINACCT) ||
044 (account_id > MAXACCT)) {
045 (void)Fchg(transf, STATLIN, 0, "Invalid account number", (FLDLEN)0);
046 tpreturn(TPFAIL, 0, transb->data, 0L, 0);
047 }
048 /* Set transaction level */
049 EXEC SQL set transaction read write;
050 /* Retrieve AMOUNT to be deleted */
051 EXEC SQL declare ccur cursor for
052 select BALANCE from ACCOUNT where ACCOUNT_ID = :account_id;
053 EXEC SQL open ccur;
054 EXEC SQL fetch ccur into :bal;
055 if (SQLCODE != SQL_OK) { /* nothing found */
056 (void)Fchg(transf, STATLIN, 0, getstr("account",SQLCODE), (FLDLEN)0);
057 EXEC SQL close ccur;
058 tpreturn(TPFAIL, 0, transb->data, 0L, 0);
059 }
060 /* Do final withdrawal */
061 /* make withdraw request buffer */
062 if ((reqfb = (FBFR *)tpalloc("FML",NULL,transb->len)) == (FBFR *)NULL) {
063 (void)userlog("tpalloc failed in close_acct\n");
064 (void)Fchg(transf, STATLIN, 0,
065 "Unable to allocate request buffer", (FLDLEN)0);
066 tpreturn(TPFAIL, 0, transb->data, 0L, 0);
067 }
068 reqlen = Fsizeof(reqfb);
069 (void)Finit(reqfb,reqlen);
070 /* put ID in request buffer */
071 (void)Fchg(reqfb,ACCOUNT_ID,0,(char *)&account_id, (FLDLEN)0);
072 /* put amount into request buffer */
073 (void)sprintf(amts,"%.2f",bal);
074 (void)Fchg(reqfb,SAMOUNT,0,amts, (FLDLEN)0);
075 /* increase the priority of this withdraw */
076 if (tps
Copyright © 2001 BEA Systems, Inc. All rights reserved.
Required browser: Netscape 4.0 or higher, or Microsoft Internet Explorer 4.0 or higher.