Improve error handling if process definition not found

[nitram509]

Since Zeebe Simple Monitor was build to support developers on local testing etc.,
I found myself in situations, where e.g. the process definition was no more available in the database.
This caused the BPMN diagram renderer to fail with exception and was confusing for me as user of Simple Monitor.

Unfortunately, I can't trace back, what caused the fact, that the process was not available, but this would be worth another PR, right? ;)
This PR just makes the renderer more robust in case of in-consistent data.

Additionally, I did replace the throw new RuntimeException() in the ViewController
with proper throw new ResponseStatusException() which will also improve/relate to PR #286 "Feature/error handler2".

Just for the record, the error can be reproduced, if someone deletes the process definition from an existing database.
When requesting a single instance, e.g. curl http://localhost:8082/views/instances/2251799814000236
the response looks like this

{
    "timestamp": "2021-08-09T15:03:04.154+00:00",
    "status": 500,
    "error": "Internal Server Error",
    "trace": "com.samskivert.mustache.MustacheException$Context: No method or field with name 'resource' on line 10
	at com.samskivert.mustache.Template.checkForMissing(Template.java:344)
	at com.samskivert.mustache.Template.getValue(Template.java:247)
	at com.samskivert.mustache.Template.getValueOrDefault(Template.java:292)
	at com.samskivert.mustache.Mustache$VariableSegment.execute(Mustache.java:872)
	at com.samskivert.mustache.Template.executeSegs(Template.java:170)
	at com.samskivert.mustache.Mustache$IncludedTemplateSegment.execute(Mustache.java:831)
	at com.samskivert.mustache.Template.executeSegs(Template.java:170)
	at com.samskivert.mustache.Template.execute(Template.java:137)
	at org.springframework.boot.web.servlet.view.MustacheView.renderMergedTemplateModel(MustacheView.java:80)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1393)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1138)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1077)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:764)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Unknown Source)
",
    "message": "No method or field with name 'resource' on line 10",
    "path": "/views/instances/2251799814000236"
}

[nitram509]

ℹ️
This is, how the implemented warning message will look like.

[saig0]

@nitram509 awesome. Thank you for this contribution 🎉

I'll review the PR soon 🚀

[CLAassistant]

All committers have signed the CLA.

[nitram509]

@saig0 I did expect, a merge conflict will occur because other PRs made changes on the same code.
I plan to fix the issue and commit&push fixes to this PR.

[saig0]

Looks good 🎉

@nitram509, it seems to work smoothly. Do you still need to adjust this PR?

[saig0]

We could merge the default case in the below Optional chain by using ifPresentOrElse().

processRepository
        .findByKey(instance.getProcessDefinitionKey())
        .map(this::getProcessResource)
        .ifPresentOrElse(
            resource -> model.put("resource", resource),
            () -> model.put("resource", WARNING_NO_XML_RESOURCE_FOUND));

[nitram509]

looks good to me as well.

[nitram509]

fine for me ... seems to result in the same behavior and avoiding the exception handling is a bit more elegant.

[nitram509]

@saig0 Looks good to me.
I was irritated, there was a merge conflict, which seems to be gone or my browser cached tricked me ;)

Nothing to do from my side, so good to merge 👍