Variable String does not support an image in base64

Good morning I have a library, which generates an image base64 from my JSP , that image sent servlet through a post , when I receive it I do not receive the full character information, maybe the string does not support the string in base64 .

Function from jsp with javascript:

function proceso(){
     var socio  = document.getElementById('socio').value;
     var foto64  = document.getElementById('foto64').value;
     f.action='/APLICACIONES/CL_T_FirmaFoto_Servlet?persona='+socio+'&foto64='+foto64;
     f.submit();
}

Reception in the servlet:

Date fec = new Date(System.currentTimeMillis());
String strCodUsu = session.getAttribute("strCodUsu")== null ? "" : (String)session.getAttribute("strCodUsu");
String strCodFoto = request.getParameter("foto64")!=null?(String)request.getParameter("foto64"):"";
String  strCodigoCliente = request.getParameter("persona")!=null?request.getParameter("persona"):"";

The system has java 6 , maybe it does not support that base64 string, I just read that the string supports up to 2gb

Here I send the image string in base64 and the amount that arrives in my string, I hope you can appreciate it

Here the number of characters that reach my servlet