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120 lines
3.5 KiB
Markdown
120 lines
3.5 KiB
Markdown
| [Home](/trick) → [Documentation Home](../Documentation-Home) → [Web Server](Webserver) → [APIs](WebServerAPIs) → Extending the HTTP API |
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## Extending the HTTP-API
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The HTTP-API is implemented as a collection of ```httpMethodHandlers```. An ```httpMethodHandler``` is a pointer to a function that is expected to respond to an HTTP GET request, using the **CivetWeb** framework. An ```httpMethodHandler``` is defined (in ```trick/CivetWeb.hh```) as follows:
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```c
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typedef void (*httpMethodHandler)(struct mg_connection *, void* cbdata);
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```
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Documentation for the **CivetWeb Networking Library** can be found at:
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[https://cesanta.com/docs/overview/intro.html](http://civetweb.github.io/civetweb/)
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## Example HTTP-API Extension
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Suppose you want your web server to send you a JSON message:
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```json
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{ "greeting" : "Hello Trick Sim Developer!" }
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```
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when you invoke the URL: ```http://localhost:8888/api/http/hello```.
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### Creating an ```httpMethodHandler```.
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The following two files will be our implementation of an ```httpMethodHandler```. We'll put these in some models directory ```httpMethods/```.
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**```handle_HTTP_GET_hello.h```**
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```c
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#ifndef HANDLE_HTTP_GET_HELLO
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#define HANDLE_HTTP_GET_HELLO
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#ifndef SWIG
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void handle_HTTP_GET_hello(struct mg_connection *nc, void *hm);
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#endif
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#endif
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```
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**```handle_HTTP_GET_hello.c```**
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```c
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#include "CivetServer.h"
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#include "civetweb.h"
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#include <string.h>
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void handle_HTTP_GET_hello(struct mg_connection *nc, void *hm) {
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mg_printf(nc, "%s", "HTTP/1.1 200 OK\r\nTransfer-Encoding: chunked\r\n\r\n");
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const char* json_text =
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"{ \"greeting\" : \"Hello Trick Sim Developer!\" }";
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mg_send_chunk(nc, json_text, strlen(json_text));
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mg_send_chunk(nc, "", 0);
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}
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```
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### Installing our ```httpMethodHandler```.
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We'll do this from our **S_define** file:
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* Add ```(httpMethods/handle_HTTP_GET_hello.c)``` to the ```LIBRARY DEPENDENCIES```.
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* Include our header file:
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```##include "httpMethods/handle_HTTP_GET_hello.h"```
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* In ```create_connections()``` add :
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```c
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web.server.installHTTPGEThandler( "hello", &handle_HTTP_GET_hello );
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```
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### A Complete S_define
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```c++
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/***********************TRICK HEADER*************************
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PURPOSE:
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(Cannon Numeric)
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LIBRARY DEPENDENCIES:
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(
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(cannon/gravity/src/cannon_init.c)
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(cannon/gravity/src/cannon_numeric.c)
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(httpMethods/handle_HTTP_GET_hello.c)
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)
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*************************************************************/
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#include "sim_objects/default_trick_sys.sm"
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#include "sim_objects/CivetServer.sm"
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##include "cannon/gravity/include/cannon_numeric.h"
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##include "httpMethods/handle_HTTP_GET_hello.h"
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class CannonSimObject : public Trick::SimObject {
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public:
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CANNON cannon ;
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int foo;
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CannonSimObject() {
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("default_data") cannon_default_data( &cannon ) ;
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("initialization") cannon_init( &cannon ) ;
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("derivative") cannon_deriv( &cannon ) ;
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("integration") trick_ret = cannon_integ( &cannon ) ;
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("dynamic_event") cannon_impact( &cannon) ;
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}
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} ;
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CannonSimObject dyn ;
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IntegLoop dyn_integloop (0.01) dyn;
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void create_connections() {
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dyn_integloop.getIntegrator(Runge_Kutta_4, 5);
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web.server.installHTTPGEThandler( "hello", &handle_HTTP_GET_hello );
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}
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```
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Continue to [Extending the WS API](Extend-ws-api) |