Problème de download d'un fichier à partir d'une JSP

Bonjour,

J'essaie d'exporter un fichier JSON (format proche de xml) à partir d'un clic sur un bouton à partir de mon jsp en passant par un OutputStream et un InputStream.
Mes codes sources ci dessous:
Action.java

Code:

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/** The inputStream */
	private InputStream inputStream;
 
 
public String exportToJsonFile()
	throws JsonMappingException, JsonGenerationException, IOException
		{
		try {
			Map<String, String> objectMap = new HashMap<String, String>();
			if(isRoleBeanChecked() != null){
				if(isRoleBeanChecked()){
					Collection<RoleBean> roleList = this.getRoleBeanService().getListRoleBean();
					String tmp = this.getRoleBeanService().exportIntoJson(roleList, false);
					objectMap.put(roleBeanKey, tmp);
				}
			}
			if(isProfileBeanChecked() != null){
				if(isProfileBeanChecked()){
					Collection<ProfileBean> profileList = this.getProfileBeanService().getListProfileBean();
					String tmp = this.getProfileBeanService().exportIntoJson(profileList, false);
					objectMap.put(profileBeanKey, tmp);
				}
			}
			//String dataToJSON = this.getRootExportBeanService().exportToJsonFile(objectMap, prettyPrint);
			String dataToJSON = this.getRootExportBeanService().exportToJsonFile(objectMap, true);
 
			InputStream anInputStream = new ByteArrayInputStream(dataToJSON.getBytes("UTF-8"));
			this.setInputStream(anInputStream);
 
 
			byte[] bytes = this.inputStreamToByte(this.getInputStream());
 
			this.sendDocumentToResponse(getServletResponse(), "testExport.txt", bytes);
 
		}
		catch (FileNotFoundException e) {
			throw new RuntimeException(e);
		} catch (StsException e) {
			this.addActionError("ihm.message.internalError");
		} /*catch (ServletException e) {
			this.addActionError("ihm.message.servletError");
			//e.printStackTrace();
		}*/
 
		this.addActionInfo("ihm.message.dataExported");
		return SUCCESS;
 
	}
 
private void sendDocumentToResponse(HttpServletResponse response, String txtFile, byte[] documentTextBytes) {
 
		OutputStream responseOutputStream = null;
		int taille;
		StringBuffer fileName;
		try {
			taille = documentTextBytes.length;
			fileName = new StringBuffer();
			fileName.append(txtFile);
			//fileName.append(".txt");
 
			response.setContentLength(taille);
			response.setContentType("application/octet-stream");
			response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName.toString() + "\"");
			response.setHeader("Pragma", "public");
			response.setHeader("Cache-Control", "cache");
			response.setHeader("Cache-control", "must-revalidate");
			responseOutputStream = response.getOutputStream();
			responseOutputStream.write(documentTextBytes);
 
			responseOutputStream.flush();
			responseOutputStream.close();
 
		} catch (Exception e) {
				try {
					if (responseOutputStream != null) {
						responseOutputStream.close();
					}
				} catch (IOException e1) {
					}
				}
			}
 
/**
         * @param inputStream the inputStream to set
         */
	public void setInputStream(InputStream inputStream) {
		this.inputStream = inputStream;
	}
 
	/**
         * @return the inputStream
         */
	public InputStream getInputStream() {
		return inputStream;
	}

mon Struts.xml

Code:

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<!-- BackupRestore Action -->
		<action name="exportToJsonFile" class="rootExportBeanAction">
			<result name="success" type="stream">
			  <param name="contentType">application/octet-stream</param>
			  <param name="inputName">inputStream</param>
			  <param name="contentDisposition">attachment; filename="testExport.txt"</param>
			  <param name="bufferSize">1024</param>
			</result>
		</action>
		<action name="initExport" class="rootExportBeanAction" method="initExport">
			<result name="success" type="tiles">InitExport</result>
		</action>

mon tile : InitExport

Code:

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<fieldset>
			<s:form action="getRootExportPopup" namespace="/">
				<table>
					<tr>
						<td><table>
							<s:checkbox labelposition="left" key="ihm.label.field.roleBeanChecked" 
							name="roleBeanChecked" value="%{roleBeanChecked}" mode="E,E,E" />
						</table></td>
					</tr>
					<tr>
						<td><table>
							<s:checkbox labelposition="left" key="ihm.label.field.profileBeanChecked"
							name="profileBeanChecked" value="%{profileBeanChecked}" mode="E,E,E" />
						</table></td>
					</tr>
				</table>
			</s:form>
		</fieldset>
 
<table>
	<tr>
	<td>
<s:submit value="Exporter" name="Exporter" method="exportToJsonFile"/></td>
 
	</tr>
</table>

Le popup apparait et me demander d'enregistrer le fichier sur le disque, mais j'ai un message sur le console :

Code:

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ERROR [[jsp]] "Servlet.service()" pour la servlet jsp a lancé une exception
java.lang.IllegalStateException: "getOutputStream()" a déjà été appelé pour cette réponse
	at org.apache.catalina.connector.Response.getWriter(Response.java:604)
	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
	at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
	at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:112)
	at 
 
.....

Merci d'avance.