HTTP_SERVLET_XML(3)

NAME
http_servlet_xml - HTTP servlet for XML requests

LIBRARY
PDEL Library (libpdel, -lpdel)

SYNOPSIS
#include <sys/types.h>
#include <stdio.h>
#include <netinet/in.h>
#include <openssl/ssl.h>
#include <pdel/http/http_defs.h>
#include <pdel/http/http_server.h>
#include <pdel/http/servlet/xml.h>
struct http_servlet *
http_servlet_xml_create(const struct http_servlet_xml_info *info, void *arg, void (*destroy)(void *));

DESCRIPTION
http_servlet_xml_create() creates a servlet that receives HTTP requests optionally containing XML and sends back XML responses. The request and response data are automatically converted to and from native binary format using the structs(3) library.

This servlet is basically acts as glue between the http_servlet(3) API and the structs_xml_input(3) and structs_xml_output(3) library routines. The net result is the ability to send and receive arbitrary data structures between two machines using XML over HTTP.

The incoming HTTP request is expected to either be a “GET” or “POST”, in the latter case with a request body containing XML. The incoming content type is ignored. The response has content type “text/xml” and contains XML.

The arg is an opaque user cookie. When the servlet is destroyed, if destroy is not NULL, it will be invoked with arg as its parameter.

info is a pointer to a struct http_servlet_xml_info:

    typedef void *http_servlet_xml_handler_t(void *arg,
                    struct http_request *req, const void *payload,
                    const char *pattrs, char **rattrsp, const char *mtype);
    struct http_servlet_xml_info {
        http_servlet_xml_handler_t  *handler;       /* user handler */
        const char                  *ptag;          /* payload doc elem */
        const struct structs_type   *ptype;         /* payload type */
        const char                  *rtag;          /* reply doc elem */
        const struct structs_type   *rtype;         /* reply type */
        u_char                      allow_post;     /* allow POST */
        u_char                      allow_get;      /* allow GET */
        http_logger_t               *logger;        /* loggging function */
        int                         flags;          /* output flags */
    };

The handler is the user routine invoked for each HTTP request (see below). ptag is the XML document tag for incoming requests. ptype is the structs(3) type for the payload data. Incoming requests that don't match ptag and ptype are rejected.

Similarly, rtag is the XML document tag for responses and rtype is the structs(3) type for the data returned by handler().

The allow_post and allow_get flags select which of “GET” and/or “POST” queries are allowed. If allow_post is zero, then ptag and ptype are ignored.

The logger is a logging function whose type is defined in http_server(3).

flags controls how XML responses are generated; this value is passed unaltered to structs_xml_output(3).

When handler() is invoked, arg is the opqaue cookie supplied to http_servlet_xml_create(), and req is the http_request(3) object. payload and pattrs will be NULL for a “GET” request, otherwise payload will point to the received data in native binary format. handler() should not free this data.

pattrs, if not NULL, points to the top level XML attributes in the request. The attributes are stored as a single sequence of concatenated pairs: name, '\0', value, '\0', name, '\0', value, etc., terminated with a final (extra) '\0'.

If top level XML attributes are desired in the response, *rattrsp should be set to a similarly concatenated list of name, value pairs allocated with typed_mem(3) type mtype.

handler() should return a pointer to the reply data in native binary format, in a region of memory allocated with typed_mem(3) type mtype. If there was an error, handler() should return NULL and set errno appropriately.

Since it's running as a servlet, the thread executing handler() may be canceled at any cancellation point. handler() should be written so as to not leak resources if this happens.

RETURN VALUES
On failure, http_servlet_xml_create() returns NULL and sets errno to an appropriate value.

SEE ALSO
http_request(3), http_response(3), http_server(3), http_servlet(3), http_servlet_xmlrpc(3), http_xml(3), libpdel(3), structs(3), typed_mem(3)

HISTORY
The PDEL library was developed at Packet Design, LLC. http://www.packetdesign.com/

AUTHORS
Archie Cobbs <archie@freebsd.org>

BUGS
http_servlet_xml_create() copies all information in info except the structs(3) types pointed to by ptype and rtype, so these must remain valid for the lifetime of the servlet. Typically structs(3) types are stored in static variables, so this is not usually a problem.