Как получить объекты из базы данных с полями, помеченными LAZY - PullRequest
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Как получить объекты из базы данных с полями, помеченными LAZY

0 голосов
/ 05 мая 2020

У меня проблема с методом findAll () в слое DAO. Наконец, он получает все объекты правильно, но имеет некоторую ошибку с "null" в процессе.

Например, в классе Group есть поле Faculty, Faculty - POJO: 

@Entity
@Table(name = "groups")
public class Group implements ModelEntity {

    @Id
    @Column(name = "group_id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "groups_seq")
    @SequenceGenerator(name = "groups_seq", sequenceName = "groups_group_id_seq", allocationSize = 1)
    private int id;

    @Column(name = "group_name")
    private String name;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "faculty_id")
    private Faculty faculty;

вот findAll () в dao: 

 @SuppressWarnings("unchecked")
    public List<T> findAll() {
        logger.debug("findAll()");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
        CriteriaQuery<T> criteriaQuery = (CriteriaQuery<T>) criteriaBuilder.createQuery(getEntityClass());
        Root<T> rootEntry = (Root<T>) criteriaQuery.from(getEntityClass());
        CriteriaQuery<T> all = criteriaQuery.select(rootEntry);
        TypedQuery<T> allQuery = entityManager.createQuery(all);
        List<T> result = allQuery.getResultList();
        logger.trace("findAll() found {} entries.", result.size());
        return result;
    }

Когда I go на сайте в / groups / getAll браузер отображает все группы и факультеты в своих столбцах, все в порядке, но в консоли я вижу java.lang.NullPointerException: null, которые начинаются с List<T> result = allQuery.getResultList();, когда я выбираю FetchType.EAGER такая же ситуация - все записи здесь, но NPE в консоли. Как обыграть NPE в консоли?

логи выглядят так: 


java.lang.NullPointerException: null
    at org.hibernate.sql.ast.SqlTreePrinter.lambda$visitQuerySpec$18(SqlTreePrinter.java:262)
    at org.hibernate.sql.ast.SqlTreePrinter.logNode(SqlTreePrinter.java:201)
    at org.hibernate.sql.ast.SqlTreePrinter.logNode(SqlTreePrinter.java:190)
    at org.hibernate.sql.ast.SqlTreePrinter.visitQuerySpec(SqlTreePrinter.java:246)
    at org.hibernate.sql.ast.SqlTreePrinter.lambda$visitStatement$0(SqlTreePrinter.java:90)
    at org.hibernate.sql.ast.SqlTreePrinter.logNode(SqlTreePrinter.java:201)
    at org.hibernate.sql.ast.SqlTreePrinter.logNode(SqlTreePrinter.java:190)
    at org.hibernate.sql.ast.SqlTreePrinter.visitStatement(SqlTreePrinter.java:88)
    at org.hibernate.sql.ast.SqlTreePrinter.print(SqlTreePrinter.java:75)
    at org.hibernate.sql.ast.spi.StandardSqlAstSelectTranslator.translate(StandardSqlAstSelectTranslator.java:85)
    at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.buildCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:232)
    at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.resolveCacheableSqmInterpretation(ConcreteSqmSelectQueryPlan.java:193)
    at org.hibernate.query.sqm.internal.ConcreteSqmSelectQueryPlan.performList(ConcreteSqmSelectQueryPlan.java:153)
    at org.hibernate.query.sqm.internal.QuerySqmImpl.doList(QuerySqmImpl.java:437)
    at org.hibernate.query.spi.AbstractQuery.list(AbstractQuery.java:1356)
    at org.hibernate.query.Query.getResultList(Query.java:136)
    at com.rumakin.universityschedule.dao.Dao.findAll(Dao.java:71)
    at com.rumakin.universityschedule.service.AuditoriumService.findAll(AuditoriumService.java:35)
    at com.rumakin.universityschedule.controllers.AuditoriumController.findAll(AuditoriumController.java:37)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    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:53)
    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:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)
03:21:08.012 [http-nio-8080-exec-12] DEBUG org.hibernate.orm.sql.ast.tree -
                SQL AST Tree:
    -> [select-statement]
      -> [query-spec]
        -> [select]
          selection - org.hibernate.sql.results.internal.SqlSelectionImpl@d1311e6a
          selection - org.hibernate.sql.results.internal.SqlSelectionImpl@429797b9
          selection - org.hibernate.sql.results.internal.SqlSelectionImpl@78d44e89
          selection - org.hibernate.sql.results.internal.SqlSelectionImpl@ea2bc8b8
        <- [select]
        -> [from]
          -> [table-group]
            -> [Auditorium as a1_0]
          <- [table-group]
        <- [from]
      <- [query-spec]
    <- [select-statement]
...