IBM AS/400E manual Writing Server API programs, Overview of the Server API, Guidelines

Chapter 7. Writing Server API programs

Overview of the Server API

The Server API allows you to extend the server’s base functions. You can write extensions to do customized processing, such as:

vEnhance the basic authentication or replace it with a site-specific process.

vAdd error handling routines to track problems or alert for serious conditions.

vDetect and track information that comes in from the requesting client, such as server referrals and user agent code.

General procedure for writing Server API programs

Before you start writing your Server API programs, you need to understand how the IBM HTTP Server works. The server performs a sequence of steps for each client request that it processes. Your program can run and make function calls at any of these steps. You need to decide where in the basic server request process you want to add customized functions. For example, do you want the server to do something after it reads a client request but before it performs any other processing? Or, maybe you want the server to perform special routines during authentication and then after it sends the requested file.

You can instruct the server to call the application functions in your program at the appropriate processing step. You can do this by using the API directives in your server configuration file.

Guidelines

Use the following guidelines when creating Server API programs:

vIf compiling on AS/400 with Integrated Language Environment (ILE)/C, ensure that you include QHTTPSVR in the library list.

vGive each of your application functions a unique function name and call the server predefined functions as needed. Be sure to include HTAPI.h and to use the HTTPD_LINKAGE macro in your function definitions to avoid abending the server. This macro ensures that all functions use the same calling conventions.

vThe server runs in a multithreaded environment; therefore, your application functions must be threadsafe. If your application is re-entrant, performance will not decrease.

vKeep the actions in your applications to a thread scope. Do not perform any actions as a process scope, such as exit or change user ID.

vEliminate global variables or protect them with a mutual exclusion semaphore.

vDo not forget to set the Content-Type header if you are using HTTPD_write() to send data back to the client.

vYou also must take into consideration the Content-Encoding header when you use HTTPD_write() to send data back to the client.

vAlways check your return codes and provide conditional processing where necessary.

vCompile and then create your service program by using CRTSRVPGM. When using CRTSRVPGM, you must bind to QZHBIAPI *SRVPGM that is in the QHTTPSVR library.

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