Exception while using the response outputstream in a Java-backed Alfresco-Share webscript

Question

1. Context

I want to implement an Alfresco-Share Java-backed webscript like the existing "I18N resources and messages Web Script". The main difference is that I want to use the response outputstream (not the writer).

Alfresco-Share version used: 4.1.1.

2. Test code used to reproduce the error

- Spring bean:

<bean id="webscript.test.content.get" parent="webscript" class="test.TestWebscript" />

- Java code:

package test;

import java.io.IOException;

import org.springframework.extensions.webscripts.AbstractWebScript;
import org.springframework.extensions.webscripts.WebScriptRequest;
import org.springframework.extensions.webscripts.WebScriptResponse;

public final class TestWebscript extends AbstractWebScript
{
    @Override
    public void execute(final WebScriptRequest request, final WebScriptResponse response) throws IOException
    {
        response.getOutputStream().write("test".getBytes());
    }
}

- Webscript desc file:

<?xml version="1.0" encoding="UTF-8"?>

<webscript>
  <shortname>Test webscript</shortname>
  <description>A webscript using the response outputstream</description>
  <url>/test/content</url>
  <format default="">extension</format>
  <lifecycle>draft_public_api</lifecycle>
  <authentication>guest</authentication>
  <transaction>required</transaction>
  <family>Tests</family>
</webscript>

3. Result

I have the exception below:

java.lang.IllegalStateException: getOutputStream() has already been called for this response
    at org.apache.catalina.connector.Response.getWriter(Response.java:611)
    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
    at org.springframework.extensions.webscripts.servlet.WebScriptServletResponse.getWriter(WebScriptServletResponse.java:198)
    at org.springframework.extensions.webscripts.LocalWebScriptRuntimeContainer.executeScript(LocalWebScriptRuntimeContainer.java:241)
    at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:377)
    at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:209)
    at org.springframework.extensions.webscripts.servlet.mvc.WebScriptView.renderMergedOutputModel(WebScriptView.java:104)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.alfresco.web.site.servlet.MTAuthenticationFilter.doFilter(MTAuthenticationFilter.java:74)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.alfresco.web.site.servlet.SSOAuthenticationFilter.doFilter(SSOAuthenticationFilter.java:355)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    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:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    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:298)
    at org.apache.coyote.http11.Http11NioProcessor.process(Http11NioProcessor.java:886)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:721)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:2256)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:662)

4. Question

Is there any way to use the webscript outputstream response?

Answer 1

This is a limitation of the WebScript Runtime on the Share web-tier. Share has a powerful component framework and extensibility model that wraps all WebScripts - enabling advanced customisations at various points in the JavaScript code, templates etc. Unfortunately treating the WebScripts as components that have their output merged together on a single page means that the Runtime controls the OutputStream and Writer - the Writer you retrieve is not the usual Servlet Writer at all but a wrapper one.