Servlets/JSP - GetOutputStream() has already been called for this response

org.apache.jasper.JasperException: java.lang.IllegalStateException: getOutputStream() has already been called for this response
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:410)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  366)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInt  erceptor.java:109)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityI  nterceptor.java:83)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilt  er.java:97)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.ja  va:100)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuth  enticationFilter.java:78)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(Securit  yContextHolderAwareRequestFilter.java:54)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilt  er.java:35)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenti  cationFilter.java:177)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(Abst  ractAuthenticationProcessingFilter.java:187)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPe  rsistenceFilter.java:79)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:  378)
	org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:167)
	org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:237)
	org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:167)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java  :88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
	net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:151)
	net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:129)
	org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter.doFilterInternal(OpenEntityManager  InViewFilter.java:113)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

<%@ page import = "java.util.*, java.text.*, java.sql.*, java.net.*,java.io.*" %>  
<%@ page import = "jxl.*" %> 
<%@ page import = "java.sql.*" %>
<%@ include file="config.jsp" %>
<%@ include file="AdHocQueries_Pers_queryConstructor.jsp" %>
<%@ include file="AdHocQueries_OT_queryConstructor.jsp" %>
<%@ include file="getRole.jsp" %> 
<%@ include file="updateUserActivity.jsp" %>
<% 


	ArrayList<String> autorized_users = new ArrayList<String>();
	autorized_users.add("HRG Full Access");
    if(isAuthorized(autorized_users,db_ipp_addr,db_name,db_username, db_password, request.getUserPrincipal().getName()) == false){
		response.sendRedirect("notAuthorized.jsp"); 
	}

	boolean noLimit = false;
	String clause = "";
	String count = "";
	if (request.getParameter("clause") != null){
	clause = request.getParameter("clause");
	}else{
		clause = "";    
	} 
	
	String OT_filter = "";
	String Pers_filter = "";
	String OT_name = "";
	String Pers_name = "";
	String OT_nr  = request.getParameter("adhocMerge_OT"); 
	String Pers_nr = request.getParameter("adhocMerge_Pers"); 
	String initialPersSql = "";
	String postPersSql = "";
	String initialOTSql = "";
	String whereclauseOTSql = "";
	String MergeSelectedField = "";
	ArrayList<String> MergeSelectedFieldList = new ArrayList<String>();
	
	String count_row_pers = "0";
	
    Connection connection = null; 
    Statement statement = null; 
    ResultSet rs = null; 
    String connectionURL = "jdbc:mysql://" + db_ipp_addr + ":3306/" + db_name;
    Class.forName("com.mysql.jdbc.Driver").newInstance(); 
    connection = DriverManager.getConnection(connectionURL, db_username, db_password); 
    statement = connection.createStatement(); 
	
	String sql = "SELECT TheSQL,Filter FROM t_L1_HRB_global_adhoc_filters_updatable WHERE Nr = '"+OT_nr+"'";
	rs = statement.executeQuery(sql); 
	if (rs.next()) { OT_filter = rs.getString("TheSQL"); OT_name= rs.getString("Filter");}

	sql = "SELECT TheSQL,Filter FROM t_L1_HRB_global_adhoc_filters_updatable WHERE Nr = '"+Pers_nr+"'";
	rs = statement.executeQuery(sql); 
	if (rs.next()) { Pers_filter = rs.getString("TheSQL"); Pers_name= rs.getString("Filter");}
	
	

	initialPersSql = getSQL(Pers_filter.toLowerCase(), true) ;
	initialPersSql = initialPersSql.substring(0,initialPersSql.indexOf("ORDER BY"));
	initialOTSql = getOTSQL(OT_filter.toLowerCase()) ;
	postPersSql = initialPersSql.replace("ifnull(PD.Stamnummer,'') as STAMNUMMER,ifnull(PD.Graad_kort,'') as GRAAD_kort,ifnull(PD.Naam,'') as NAAM,ifnull(PD.Voornamen,'') as VOORNAMEN, ifnull(PD.Org,'') as ORG, ifnull(PD.orgnum,'') as ORGNUM ,","ifnull(PD.Stamnummer,'') as STAMNUMMER,");

	sql = "SELECT Table_Name_DB, FieldName_DB FROM t_L1_HRB_global_adhoc_selectfields WHERE AdHocType  = '1'";
			rs = statement.executeQuery(sql);
			String tempo = postPersSql.substring(postPersSql.indexOf("SELECT"), postPersSql.indexOf("FROM")).toLowerCase();
			while (rs.next()) { 
				if ((tempo.contains("pd."+rs.getString("FieldName_DB").toLowerCase()+",") ^ tempo.contains(rs.getString("Table_Name_DB")+"1"+rs.getString("FieldName_DB").toLowerCase()+",")) && !MergeSelectedField.toLowerCase().contains(rs.getString("FieldName_DB").toLowerCase())){
					MergeSelectedField+= ",T2."+rs.getString("FieldName_DB");
					if (!rs.getString("FieldName_DB").equals("Stamnummer")) MergeSelectedFieldList.add(rs.getString("FieldName_DB"));
				};
			}
			MergeSelectedField = MergeSelectedField.replace(",T2.Stamnummer","");		

	whereclauseOTSql = initialOTSql.substring(initialOTSql.indexOf("WHERE"));

	sql = "SELECT * "+MergeSelectedField+" FROM t_L1_HRB_global_org_ot AS OT LEFT JOIN ("+postPersSql+") AS T2 ON OT.Stamnummer = T2.Stamnummer " +whereclauseOTSql;



String sheetname = "Global "+version+" : Ad Hoc query OT"; 
OutputStream os = response.getOutputStream();// will write to the output stream WritableWorkbook 

	
 
   try{  
   response.reset ();  
   response.setContentType ( "application / vnd.ms-excel; charset = UTF-8");  
   response.setHeader ( "Content-Disposition", "attachment; filename =" + new String ( (sheetname+".xls").getBytes (), "iso-8859-1"));  

   int NrToAdd = MergeSelectedFieldList.size();
    
   jxl.write.WritableWorkbook wwb = jxl.Workbook.createWorkbook (os); 
   jxl.write.WritableSheet ws = wwb.createSheet ( sheetname, 0);  
   ws.getSettings().setOrientation(jxl.format.PageOrientation.LANDSCAPE);
   ws.getSettings().setScaleFactor(50);
   ws.getSettings().setFitWidth(1);
   ws.getSettings().setPaperSize(jxl.format.PaperSize.A3);
   HeaderFooter footer = new HeaderFooter();

...

OutputStream os = response.getOutputStream();