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I'm working with a micro-service built using Java 11, this service has a dependency built in Java 8. Dependency has rest-clients in it and there is a method that does this:
public <T> ResponseEntity<my.company.Wrapper<T>> getForList(String url, HttpHeaders headers) {
try {
return template.exchange(url, GET, new HttpEntity<>(headers), new ParameterizedTypeReference<Wrapper<T>>() { });
} catch (RestClientException restEx) {
logger.error("RestClientException!, restEx: {}", restEx);
throw restEx;
}
}
Rest call is just successful,
response -> <200,Wrapper [ elements = [{id=dbfc2557-1738-45e4-8ecd-235d35158957, .....
then, at micro-service (with Java 11), there is a point when it uses a java Stream:
var found = enttsResponse.stream()
.map(MyCompanyResponse::getId)
.collect( toList() );
Exception message is:
java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class com.mycompany.commons.v2.entitlement.MyCompanyResponse (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; com.mycompany.commons.v2.entitlement.MyCompanyResponse is in unnamed module of loader 'app')
I'm familiar to Java8, but not Java 11, I think is something related to Class Loaders (from Java 9)
Workaround are accepted, thanks in advance !!!
Full stack trace:
java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class com.mycompane.commons.v2.entitlement.MyCompanyResponse (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; com.mycompane.commons.v2.entitlement.MyCompanyResponse is in unnamed module of loader 'app')
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195) ~[na:na]
at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1654) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) ~[na:na]
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913) ~[na:na]
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:na]
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578) ~[na:na]
at com.mycompane.service.organization.core.SomeAmazingService.validateEntitlements(OrganizationService.java:105) ~[main/:na]
at com.mycompane.service.organization.core.SomeAmazingService.createOrganization(OrganizationService.java:66) ~[main/:na]
at com.mycompane.service.organization.core.SomeAmazingService$$FastClassBySpringCGLIB$$490b1633.invoke(<generated>) ~[main/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:295) ~[spring-tx-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:98) ~[spring-tx-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688) ~[spring-aop-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at com.mycompane.service.organization.core.SomeAmazingService$$EnhancerBySpringCGLIB$$7e4fe77b.createOrganization(<generated>) ~[main/:na]
at com.mycompane.service.organization.web.OrganizationController.createOrganization(OrganizationController.java:53) ~[main/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.boot.actuate.web.trace.servlet.HttpTraceFilter.doFilterInternal(HttpTraceFilter.java:88) ~[spring-boot-actuator-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:119) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at com.mycompane.commons.v2.security.JwtAuthenticationTokenFilter.successfulAuthentication(JwtAuthenticationTokenFilter.java:68) ~[spring-commons-2.63.jar:na]
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:240) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:74) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.cloud.sleuth.instrument.web.ExceptionLoggingFilter.doFilter(ExceptionLoggingFilter.java:50) ~[spring-cloud-sleuth-core-2.1.2.RELEASE.jar:2.1.2.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at brave.servlet.TracingFilter.doFilter(TracingFilter.java:99) ~[brave-instrumentation-servlet-5.6.5.jar:na]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.filterAndRecordMetrics(WebMvcMetricsFilter.java:114) ~[spring-boot-actuator-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:104) ~[spring-boot-actuator-2.1.6.RELEASE.jar:2.1.6.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]
712
// type cast an parent type to its child type. In order to deal with ClassCastException be careful that when you're trying to typecast an object of a class into another class ensure that the new type belongs to one of its parent classes or do not try to typecast a parent object to its child type.
Just like HashMap, LinkedHashMap implementation is not synchronized. So if you are going to access it from multiple threads and at least one of these threads is likely to change it structurally, then it must be externally synchronized. It's best to do this at creation: Map m = Collections.
The LinkedHashMap class of the Java collections framework provides the hash table and linked list implementation of the Map interface. The LinkedHashMap interface extends the HashMap class to store its entries in a hash table. It internally maintains a doubly-linked list among all of its entries to order its entries.
There are basically two ways to iterate over LinkedHashMap: Using keySet() and get() Method. Using entrySet() and Iterator.
You have a type token of the form new ParameterizedTypeReference<Wrapper<T>>() { }, referring to a type variable. This doesn’t work due to type erasue (the reason why such type tokens exist in the first place).
The framework receiving the type token will only know that it has to produce a Wrapper, but still doesn’t know what T is. So it doesn’t know what to produce and will fall back to collections (i.e. LinkedHashMap).
You have to replace the caller of the generic method with an expression referring to the known reifiable type, i.e.
template.exchange(uriBuilder.toUriString(), GET, new HttpEntity<>(headers),
new ParameterizedTypeReference<Wrapper<EntitlementResponse>>() { })
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