Jasper - Relatório em branco

package util.jasper;

import java.sql.*;
import net.sf.jasperreports.engine.*;
import net.sf.jasperreports.view.*;
import java.io.*;
import java.util.*;

public class ChamaRel {
    private final String URL_JDBC="jdbc:mysql://localhost/bancodois";
    private final String DB_USER ="teste";
    private final String DB_PASS ="12345";
    
    public ChamaRel() {
    
    }

    private Connection getConexao(){
        Connection cnn=null;
        try{         Class.forName("com.mysql.jdbc.Driver");
        cnn=DriverManager.getConnection(URL_JDBC, DB_USER, DB_PASS);
        } catch (Exception ex){
            System.out.println("Erro na conexão com banco: " + ex.getMessage());
        }
        return cnn;
    }
    
    public void runRel(String pathRel, Map params, OutputStream out){

        try {
            
            JasperReport jr = JasperCompileManager.compileReport(pathRel);
            
            JasperPrint jp = JasperFillManager.fillReport(jr, params, this.getConexao());

            JasperExportManager.exportReportToPdfStream(jp, out);
            
        }    
        catch (Exception ex) 
        {
            System.out.println("Erro na geração do relatório: " + ex.getMessage());
        }
    }
    
    
}

27/05/2008 17:18:15 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response


        at org.apache.catalina.connector.Response.getWriter(Response.java:610)
        at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
        at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
        at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
        at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:186)
        at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
        at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)
        at org.apache.jsp.aula1003.exec_005fcarros_jsp._jspService(exec_005fcarros_jsp.java:84)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
        at java.lang.Thread.run(Thread.java:619)