Lets write out first CppCMS based application: |
Lets write our first CppCMS based application: |
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First we create a file called hello.cpp and store in |
it the following content. |
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_Includes:_ |
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We should import some definitions for our 1st application: |
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- `cppcms/application.h` - the class `application` that every CppCMS application is derived from. |
- `cppcms/applications_pool.h` - class `applications_pool` - the class that manages user applications - creates new per HTTP request and caches them for future use. |
- `cppcms/service.h` - the service - central event loop of the network service. |
- `cppcms/http_response.h` the class we write our response to the client with. |
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So let's include them all. |
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#include <cppcms/application.h> |
#include <cppcms/applications_pool.h> |
#include <cppcms/service.h> |
#include <cppcms/http_response.h> |
#include <iostream> |
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Now we define our first application class, that is |
derived from `cppcms::application`. It should receive |
in its constructor a reference to the central CppCMS service |
that runs our application. |
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class hello : public cppcms::application { |
public: |
hello(cppcms::service &srv) : |
cppcms::application(srv) |
{ |
} |
virtual void main(std::string url); |
}; |
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At this point, in order to respond on user request we |
just override `cppcms::application::main` member |
function that is always called per each request. |
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In this function we will simply write HTML to the output stream. The output stream can be accessed using the `response` member function of the `application` class that gives us access to the output stream `out()`. |
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void hello::main(std::string /*url*/) |
{ |
response().out() << |
"<html>\n" |
"<body>\n" |
" <h1>Hello World</h1>\n" |
"</body>\n" |
"</html>\n"; |
} |
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Now lets setup our main function. First we create the |
service class that parses command line parameters and searches for configuration options |
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int main(int argc,char ** argv) |
{ |
try { |
cppcms::service srv(argc,argv); |
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Then we tell the `applications_pool` class to use our application - `hello` - by providing it a predefined |
object factory `cppcms::applications_factory<hello>()`. We then so call mount our application to the pool so it will |
be used for request handling. |
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srv.applications_pool().mount( |
cppcms::applications_factory<hello>() |
); |
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And now we run our event loop. The `run()` function |
exits when the process receives `SIGINT`, `SIGTERM` or `SIGUSR1` signal. |
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srv.run(); |
} |
catch(std::exception const &e) { |
std::cerr << e.what() << std::endl; |
} |
} |
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That's it, our application is ready, now we can compile it as simply as: |
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c++ hello.cpp -lcppcms -o hello |
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Now we need to prepare the configuration file `config.js` that uses JSON file format for passing all options: |
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{ |
"service" : { |
"api" : "http", |
"port" : 8080 |
}, |
"http" : { |
"script_names" : [ "/hello" ] |
} |
} |
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We setup our service to listen on port 8080 using HTTP |
protocol (it is very useful for debugging our applications). |
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We also provide the `script_names` parameter that defines |
the path to the virtual "CGI Scripts" or in simple words |
the path that our application should be called from. |
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Now we can start the application |
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./hello -c config.js |
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Go to our browser and hit <http://localhost:8080/hello> |
link to see our first CppCMS application working. |
