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Starting With Sessions

General

In this tutoring we would show the basics of using sessions in CppCMS --- how to store connection persistent data in stateless HTTP protocol.

Code

Our current code would be based on start with forms code.

Templates and Content

We would save the information about user using session_interface object that is a member of application. This information would be displayed every time it visits the page.

First of all let's change our "data.h": Instead of showing person's sex and state we should display a prefix "Mr", "Miss" or "Mrs" according to our saved parameters.

So lets change line:

string name,state,sex;

to

string name,who;

And we would use following template:

<h1>Hello <% who %> <% name %></h1>
<% if (content.age != -1.0) %>
    <p>Your age is <% age %></p>
    <h2>Change details</h2>
<% else %>
    <h2>Input your details</h2>
<% end %>
<form method="post" action="" >
<% form as_p info %>
</form>

Notes: We can inject arbitrary C++ code into conditions between two brackets () (line 2). However, now we should refer to all content class variables using content member. Templates engine would not substitute correct prefix for you, because it is native C++ code.

Saving data

Now let's rewrite out hello::info function:

First of all let's load new data from the form when it submitted to session object, instead of content. This information is preserved withing different requests:

data::message c;
if(env->getRequestMethod()=="POST") {
        c.info.load(*cgi);
        if(c.info.validate()) {
                session["name"]=c.info.name.get();
                session["sex"]=c.info.sex.get();
                session["state"]=c.info.martial.get();
                session.set("age",c.info.age.get());
                c.info.clear();
        }
}

Notes:

Now, our session data would be preserved between requests and we can fetch it:

Fetching Data

if(session.is_set("name")) {
    c.name=session["name"];
    if(session["sex"]=="Male") {
            c.who="Mr";
    }
    else {
            if(session["state"]=="Single") {
                    c.who="Miss";
            }
            else {
                    c.who="Mrs";
            }
    }
    c.age=session.get<double>("age");
}
else {
    c.name="Visitor";
    c.age=-1;
}
render("message",c);

Notes:

Configuration --- behind the scenes

Storage Backend

CppCMS has several options to session management. In every case cookies are used --- there is no "GET" or "POST" methods for storing session information like /page/?sid=2e7f60c43b88d4b554a.

The developer has several options to save information:

We would add following lines to our CppCMS configuration file:

session.location = "client" 
session.cookies_key = "10b74ef35431d95c420dc67b52b3f166"

Notes:

Duration Options

You can define several session duration options:

Each type of expiration has its time limit (even browser one has its limit). It can be defined using session.timeout parameter. The default one is 24 hours.

For example:

session.expire = "renew"
session.timeout = 604800 # Week

About

CppCMS is a web development framework for performance demanding applications.

Commercial

CppCMS is available under Open Source and Commercial Licenses.

For more details, visit our website: commercial.cppcms.com

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