This recipe has only this single servlet:
@WebServlet(name = "ServerPushServlet", urlPatterns =
{"/ServerPushServlet"})
public class ServerPushServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doRequest(request, response);
}
private void doRequest(HttpServletRequest request,
HttpServletResponse response) throws IOException{
String usePush = request.getParameter("usePush");
if ("true".equalsIgnoreCase(usePush)){
PushBuilder pb = request.newPushBuilder();
if (pb != null) {
for(int row=0; row < 5; row++){
for(int col=0; col < 8; col++){
pb.path("image/keyboard_buttons/keyboard_buttons-"
+ row + "-" + col + ".jpeg")
.addHeader("content-type", "image/jpeg")
.push();
}
}
}
}
try (PrintWriter writer = response.getWriter()) {
StringBuilder html = new StringBuilder();
html.append("<html>");
html.append("<center>");
html.append("<table cellspacing='0' cellpadding='0'
border='0'>");
for(int row=0; row < 5; row++){
html.append(" <tr>");
for(int col=0; col < 8; col++){
html.append(" <td>");
html.append("<img
src='image/keyboard_buttons/keyboard_buttons-" +
row + "-" + col + ".jpeg' style='width:100px;
height:106.25px;'>");
html.append(" </td>");
}
html.append(" </tr>");
}
html.append("</table>");
html.append("<br>");
if ("true".equalsIgnoreCase(usePush)){
html.append("<h2>Image pushed by ServerPush</h2>");
} else{
html.append("<h2>Image loaded using HTTP/1.0</h2>");
}
html.append("</center>");
html.append("</html>");
writer.write(html.toString());
}
}
}
And we creat a simple page to call both HTTP/1.0 and HTTP/2.0 cases:
<body>
<a href="ServerPushServlet?usePush=true">Use HTTP/2.0 (ServerPush)</a>
<br />
<a href="ServerPushServlet?usePush=false">Use HTTP/1.0</a>
</body>
And try it on a Java EE 8 compatible server using this URL:
https://localhost:8181/ch04-serverpush