How to handle file upload with apache-camel restlet component? - apache-camel

Question

I have a front end web-application that uploads a file and other data via a simple form:
<form action="/document/invoice/entity/777" enctype="multipart/form-data">
<input name="file" type="file">
<input name="userId">
<button>Upload File</button>
</form>
and the server side has to be a apache-camel route that handles the uploaded data with restlet component, something similar to this:
<restContext id="myApi" xmlns="http://camel.apache.org/schema/spring">
<rest path="/document">
<post uri="/{documentType}/entity/{entityId}" outType="documentService.Result"
consumes="multipart/form-data" produces="application/json">
<route>
<to uri="bean:documentService?method=validate(${body.file}, ${body.userId}, ${header.documentType}, ${header.entityId})"/>
</route>
</post>
</rest>
</restContext>
With this configuration I'm getting this error:
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.Gson.fromJson(Gson.java:822)
at com.google.gson.Gson.fromJson(Gson.java:748)
at org.apache.camel.component.gson.GsonDataFormat.unmarshal(GsonDataFormat.java:105)
at org.apache.camel.processor.UnmarshalProcessor.process(UnmarshalProcessor.java:67)
at org.apache.camel.processor.binding.RestBindingProcessor.process(RestBindingProcessor.java:175)
at org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:77)
at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:448)
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:191)
at org.apache.camel.processor.Pipeline.process(Pipeline.java:118)
at org.apache.camel.processor.Pipeline.process(Pipeline.java:80)
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:191)
at org.apache.camel.util.AsyncProcessorHelper.process(AsyncProcessorHelper.java:109)
at org.apache.camel.processor.DelegateAsyncProcessor.process(DelegateAsyncProcessor.java:87)
at org.apache.camel.component.http.CamelServlet.service(CamelServlet.java:144)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:537)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1085)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1556)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1513)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:387)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:183)
at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145)
at com.google.gson.Gson.fromJson(Gson.java:810)
... 36 more
How can I upload files and other data to an apache-camel rest endpoint?

Answer 1

Looks like you have a few configuration issues for how you are passing your data to the restlet component of camel. I would recommend reading the restlet documentation on the camel site: http://camel.apache.org/restlet.html And if you are still having problems here is a link to a full project implementing the restlet server with camel:
http://www.ofbizian.com/2012/02/apache-camel-rest-example.html.
If you are still having issues after checking out those resources please clarify if that exception was from the client or server side.

Answer 2

You are trying to upload some data or file but according to the error it is expecting JSON data, "com.google.gson.JsonSyntaxException" and instead it gets something else. Are you sure the backend part is configured correctly according to what you are sending?