spring boot + mybatis puls + thymeleaf ，thymeleaf获取list中的map对象报错FTL stack trace ("~" means nesting

求给位大佬帮忙解决下，我用的项目的是 spring boot + mybatis puls + thymeleaf：

情况是这样的，我后台获取List>这样的数据返回给前面thymeleaf模板。

到thymeleaf模板页面就报错了，如下：

[2018-05-11 13:44:35.337] ERROR freemarker.runtime [http-nio-8888-exec-1] Error executing FreeMarker template
freemarker.core.NonStringOrTemplateOutputException: For "${...}" content: Expected a string or something automatically convertible to string (number, date or boolean), or "template output" , but this has evaluated to a sequence (wrapper: f.t.SimpleSequence):
==> playList?if_exists  [in template "start.html" at line 98, column 43]

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${playList?if_exists}  [in template "start.html" at line 98, column 41]
----
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:511)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:389)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:358)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:330)
	at freemarker.core.Environment.visit(Environment.java:336)
	at freemarker.core.Environment.process(Environment.java:309)
	at freemarker.template.Template.process(Template.java:384)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:396)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:309)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:257)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:165)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:314)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1325)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1069)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1008)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
 [2018-05-11 13:44:35.357] ERROR o.a.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] [http-nio-8888-exec-1] Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is freemarker.core.NonStringOrTemplateOutputException: For "${...}" content: Expected a string or something automatically convertible to string (number, date or boolean), or "template output" , but this has evaluated to a sequence (wrapper: f.t.SimpleSequence):
==> playList?if_exists  [in template "start.html" at line 98, column 43]

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${playList?if_exists}  [in template "start.html" at line 98, column 41]
----] with root cause
freemarker.core.NonStringOrTemplateOutputException: For "${...}" content: Expected a string or something automatically convertible to string (number, date or boolean), or "template output" , but this has evaluated to a sequence (wrapper: f.t.SimpleSequence):
==> playList?if_exists  [in template "start.html" at line 98, column 43]

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${playList?if_exists}  [in template "start.html" at line 98, column 41]
----
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:511)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:389)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:358)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:330)
	at freemarker.core.Environment.visit(Environment.java:336)
	at freemarker.core.Environment.process(Environment.java:309)
	at freemarker.template.Template.process(Template.java:384)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:396)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:309)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:257)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:165)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:314)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1325)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1069)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1008)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:745)
 [2018-05-11 13:44:35.424] ERROR o.s.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration$SpelView [http-nio-8888-exec-1] Cannot render error page for request [/start] and exception [For "${...}" content: Expected a string or something automatically convertible to string (number, date or boolean), or "template output" , but this has evaluated to a sequence (wrapper: f.t.SimpleSequence):
==> playList?if_exists  [in template "start.html" at line 98, column 43]

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${playList?if_exists}  [in template "start.html" at line 98, column 41]
----] as the response has already been committed. As a result, the response may have the wrong status code.

Controller层代码如下：

@RequestMapping("/start")
    public ModelAndView getMusic(ModelAndView mv,HttpServletRequest request) {
        try {
            int pageNo = 0;
            if(null != request.getParameter("pageNo")){
                pageNo = Integer.valueOf(request.getParameter("pageNo").toString());
            }
            
            List> listMusic = musicServiceInterface.getListMusic(pageNo);
           

            mv.setViewName("start");
            mv.addObject("src","file/"+musicName);
            mv.addObject("playList",listMusic);
            return mv;
        } catch (Exception e) {
            e.printStackTrace();
            return mv;
        }
    }
}

thymeleaf模板页面如下：

    

        演示数据
    

pom.xml代码:

                
			org.springframework.boot
			spring-boot-starter-thymeleaf
		

		
		
			net.sourceforge.nekohtml
			nekohtml
			1.9.22
		

application.properties代码如下:

spring.thymeleaf.prefix=classpath:/templates/
spring.thymeleaf.suffix=.html
spring.thymeleaf.mode=LEGACYHTML5
spring.thymeleaf.encoding=UTF-8
spring.thymeleaf.servlet.content-type=text/html
spring.thymeleaf.cache=false