How to return single object using NativeSearchQueryBuilder of ElasticSearch in Spring Project?

Question

I am using NativeSearchQueryBuilder to form the Query as follows:

 String[] includeFields = new String[]{"idDl", "clientName"};
 String[] excludeFields = new String[]{"Address"};
 Query searchQuery = new NativeSearchQueryBuilder()
                .withQuery(matchQuery("idDl", idDl))
                .withSourceFilter(new FetchSourceFilter(includeFields, excludeFields))
                 .build();
return elasticsearchRestTemplate.queryForObject((StringQuery) searchQuery, User.class);

I want to return single object without the certain fields and this is the Stack-trace of the exception:

java.lang.ClassCastException: org.springframework.data.elasticsearch.core.query.NativeSearchQuery cannot be cast to org.springframework.data.elasticsearch.core.query.StringQuery
at com.user.services.UserQueryServiceImpl.getUserById(UserQueryServiceImpl.java:37) ~[classes/:na]
at com.User.controllers.UserController.getFilteredUserById(UserController.java:100) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.5.RELEASE.jar:5.2.5.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.33.jar:9.0.33]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.33.jar:9.0.33]

Answer 1

First queryForObject is deprecated, you should use searchOne(). As for your error:

You create a NativeSearchQuery, assigne it to the variable searchQuery which is of type Query; that's alright. But why do you try to cast this to a StringQuery?

NativeSearchQuery and StringQuery both implement Query, so just pass your query instance:

return elasticsearchRestTemplate.queryForObject(searchQuery, User.class)

Edit for Spring Data Elasticsearch 3.2.x:

You should use

<T> List<T> queryForList(SearchQuery query, Class<T> clazz);

as in that version there was still the SearchQuery interface that NativeSearchQueryimplements. From the returned list, check if it contains any elements and then use the first one.