Save an image on my server with javascript, jsp, html, java

Question

I really need your help for saving a simple image generate with google charts on my server for using it on a PDF export.

My PDF export already works but I cant put my image in it.

For the creation of my image I use it :

function drawChart() {       
    var dataAge = google.visualization.arrayToDataTable([       //Table data
            ['Tranche âge', 'Population'],                      //Column name
            ['Moins de 15 ans', <fmt:formatNumber value="${p_0015}" maxFractionDigits="0" groupingUsed="false" />],          
            ['De 15 à 19 ans', <fmt:formatNumber value="${p_1519}" maxFractionDigits="0" groupingUsed="false" />],
            ]);
    var optionsAge = {                                          //Table options
        title: 'Répartition de la population selon son âge',
        width:600,
        height:300,
    };

    google.visualization.events.addListener(chart, 'ready', function () {
        chart_div.innerHTML = '<img src="' + chart.getImageURI() + '">';
        console.log(chart_div.innerHTML);
    });
    chart.draw(dataAge, optionsAge);
}

And for show it, I just have to use this :

<div id='chart_div'></div>

I just want to save the image who's created by that div on my server (in a temporary folder who is deleted ) for using it. I can use javascript, java, or html.

Thanks for your help :)