This probably occurs when importing various Swagger JSONs, but I got this error importing the Swagger JSON from KIE Server, part of jBPM by Red Hat. The same JSON is imported on Postman just fine.
This is a disappointment, because Swagger "is supported by SmartBear", and so is SoapUI. It is clearly an API issue within SoapUI itself. Below is the stack trace from soapui-errors.log, in case anybody's looking into it:
2019-04-25 10:10:24,072 ERROR [errorlog] groovy.lang.MissingPropertyException: No such property: sampleContent for class: com.eviware.soapui.impl.rest.RestRepresentation
groovy.lang.MissingPropertyException: No such property: sampleContent for class: com.eviware.soapui.impl.rest.RestRepresentation
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:53)
at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.setProperty(ScriptBytecodeAdapter.java:486)
at com.smartbear.swagger.Swagger2Importer$_addOperation_closure3_closure7_closure8.doCall(Swagger2Importer.groovy:194)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1019)
at groovy.lang.Closure.call(Closure.java:426)
at groovy.lang.Closure.call(Closure.java:442)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:5228)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2107)
at org.codehaus.groovy.runtime.dgm$163.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:274)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:56)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callSafe(AbstractCallSite.java:87)
at com.smartbear.swagger.Swagger2Importer$_addOperation_closure3_closure7.doCall(Swagger2Importer.groovy:191)
at sun.reflect.GeneratedMethodAccessor102.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1019)
at groovy.lang.Closure.call(Closure.java:426)
at groovy.lang.Closure.call(Closure.java:442)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2030)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2015)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2056)
at org.codehaus.groovy.runtime.dgm$162.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:274)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:56)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callSafe(AbstractCallSite.java:87)
at com.smartbear.swagger.Swagger2Importer$_addOperation_closure3.doCall(Swagger2Importer.groovy:186)
at sun.reflect.GeneratedMethodAccessor112.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1019)
at groovy.lang.Closure.call(Closure.java:426)
at groovy.lang.Closure.call(Closure.java:442)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:5228)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2107)
at org.codehaus.groovy.runtime.dgm$163.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:274)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:56)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callSafe(AbstractCallSite.java:87)
at com.smartbear.swagger.Swagger2Importer.addOperation(Swagger2Importer.groovy:171)
at com.smartbear.swagger.Swagger2Importer$addOperation.callCurrent(Unknown Source)
at com.smartbear.swagger.Swagger2Importer.importPath(Swagger2Importer.groovy:114)
at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:384)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1019)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:69)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:182)
at com.smartbear.swagger.Swagger2Importer$_importSwagger_closure1.doCall(Swagger2Importer.groovy:74)
at sun.reflect.GeneratedMethodAccessor126.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1019)
at groovy.lang.Closure.call(Closure.java:426)
at groovy.lang.Closure.call(Closure.java:442)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:5228)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:2107)
at org.codehaus.groovy.runtime.dgm$163.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:274)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:56)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125)
at com.smartbear.swagger.Swagger2Importer.importSwagger(Swagger2Importer.groovy:73)
at com.smartbear.swagger.SwaggerImporter$importSwagger.call(Unknown Source)
at com.smartbear.swagger.SwaggerUtils$1.construct(SwaggerUtils.groovy:75)
at com.eviware.soapui.support.swing.SwingWorkerDelegator.construct(SwingWorkerDelegator.java:46)
at com.eviware.soapui.support.swing.SwingWorker$2.run(SwingWorker.java:131)
at java.lang.Thread.run(Unknown Source)
I'm a big fan of SOAPUI but I've found SOAPUI's swagger import disappointing and so unreliable I've stopped trying. Instead I've found the most success by use one of the many online tools that convert the swagger files to a WADL and import that instead. If that fails, you will likely get enough information to handball fixes into the wadl, but that might be because I'm far more familiar with WADL than swagger, having started out coding those by hand before I found SOAPUI.