[FIXED] Spring MVC Model.containsAttribute Invoked method is no accessor method

Issue

I'm going back to some code I wrote back in 2016, running it now when the following controller method is invoked, it fails on the last line

    @RequestMapping(value = "", method = RequestMethod.GET, produces = "text/html")
    public String getCharacterSheet(@PathVariable("author") String author, @PathVariable("game") String game, @PathVariable("version") String version, Model model, HttpServletRequest request, @AuthenticationPrincipal String currentUser) {
        try {
            PluginDescription description = new PluginDescription(URLDecoder.decode(author, "UTF-8"),
                    URLDecoder.decode(game, "UTF-8"),
                    URLDecoder.decode(version, "UTF-8"));
            Optional<GamePlugin<Character>> plugin = plugins.getPlugin(description);
            if (!plugin.isPresent()) {
                throw new MissingPluginException(description);
            }
            CharacterDataWrapper wrapper;
            if (model.containsAttribute("character-wrapper")) {

The exception which occurrs is

java.lang.IllegalArgumentException: Invoked method public abstract boolean org.springframework.ui.Model.containsAttribute(java.lang.String) is no accessor method!
    org.springframework.util.Assert.notNull(Assert.java:115)
    org.springframework.data.projection.MapAccessingMethodInterceptor$Accessor.<init>(MapAccessingMethodInterceptor.java:97)
    org.springframework.data.projection.MapAccessingMethodInterceptor.invoke(MapAccessingMethodInterceptor.java:62)
    org.springframework.data.projection.ProjectingMethodInterceptor.invoke(ProjectingMethodInterceptor.java:75)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.data.projection.ProxyProjectionFactory$TargetAwareMethodInterceptor.invoke(ProxyProjectionFactory.java:218)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:61)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213)
    com.sun.proxy.$Proxy134.containsAttribute(Unknown Source)
    io.github.thisisnozaku.charactercreator.controllers.games.GamePagesController.getCharacterSheet(GamePagesController.java:77)

One thing I don't understand, why model is what appears to be a proxy wrapping a Map, instead of an implementation of Model.

Solution

I was unable to determine the real cause of this. However, when examining my Gradle dependencies, I noticed that there were multiple versions of Spring expected.

Upgrading my version of Spring Boot to the latest 1.5.x version resolved the issue.

Answered By - ThisIsNoZaku