JsonMappingException：无法初始化代理 - 没有会话

JsonMappingException: could not initialize proxy - no Session

提问by greyfox

I am building a RESTful Web Service that consumes and returns JSON. I am encountering the following stack trace when I try to fetch an ESRBRating object from the database through the service layer. However when I inject the Spring Data JPA repository directly to the controller and use that to fetch the ESRBRating by ID it works fine. However when calling through the service layer it does not work. I have provided the stack trace and code below. Can someone explain to me why this is happening when going through a service layer but not when going through the Spring Data JPA repository directly? How do I resolve this issue?

我正在构建一个使用并返回 JSON 的 RESTful Web 服务。当我尝试通过服务层从数据库中获取 ESRBRating 对象时，我遇到了以下堆栈跟踪。但是，当我将 Spring Data JPA 存储库直接注入控制器并使用它来按 ID 获取 ESRBRating 时，它工作正常。但是当通过服务层调用时它不起作用。我在下面提供了堆栈跟踪和代码。有人可以向我解释为什么在通过服务层时会发生这种情况，而不是在直接通过 Spring Data JPA 存储库时发生这种情况吗？我该如何解决这个问题？

Stack Trace

堆栈跟踪

Caused by: org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:165)
    at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:286)
    at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
    at net.jkratz.igdb.model.ESRBRating_$$_jvst319_0.getId(ESRBRating_$$_jvst319_0.java)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at com.fasterxml.Hymanson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466)
    at com.fasterxml.Hymanson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
    ... 76 more

Controller

控制器

@RestController
@RequestMapping(produces = "application/json", value="/esrbrating")
public class ESRBRatingController {

    @Inject
    ESRBRatingService esrbRatingService;

    @Inject
    ESRBRatingRepository esrbRatingRepository;

    private Logger logger = LoggerFactory.getLogger(getClass());

    /**
     * Returns all ESRB ratings in database
     * 
     * @return List of ESRBRating objects
     * @see ESRBRating
     */
    @RequestMapping(value = {"","/"}, method = RequestMethod.GET)
    public ResponseEntity<List<ESRBRating>> getESRBRatings() {
        List<ESRBRating> esrbRatings = esrbRatingService.getESRBRatings();
        return new ResponseEntity<>(esrbRatings, HttpStatus.OK);
    }

    /**
     * Returns a single ESRB rating object if exists, otherwise returns HTTP status code 404
     *
     * @param id ID of the ESRB Rating
     * @return ESRB Rating when found
     * @see ESRBRating
     */
    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    public ResponseEntity<?> getUser(@PathVariable("id") Long id) {
        logger.debug("Attempting to fetch ESRB rating with ID: {}", id);
        ESRBRating esrbRating = esrbRatingService.getESRBRating(id);
        //ESRBRating esrbRating = esrbRatingRepository.findOne(id);

        if (esrbRating == null) {
            return new ResponseEntity<>("ESRB Rating not found", HttpStatus.NOT_FOUND);
        } else {
            return new ResponseEntity<>(esrbRating, HttpStatus.OK);
        }
    }

}

Service

服务

@Service
@Transactional
public class ESRBRatingServiceImpl implements ESRBRatingService {

    @Value("#{paging.games.maxPageSize}")
    private static int DEFAULT_PAGE_SIZE;

    @Value("#{paging.games.maxPageSize}")
    private static int MAX_PAGE_SIZE;

    @Inject
    private ESRBRatingRepository esrbRatingRepository;

    @Override
    public List<ESRBRating> getESRBRatings() {
        List<ESRBRating> ratings =  esrbRatingRepository.findAll();
        return ratings;
    }

    @Override
    public ESRBRating getESRBRating(Long id) {
        return esrbRatingRepository.getOne(id);
    }

    @Override
    public ESRBRating saveESRBRating(ESRBRating esrbRating) {
        return esrbRatingRepository.saveAndFlush(esrbRating);
    }

    @Override
    public boolean deleteESRBRating(Long id) {
        esrbRatingRepository.delete(id);
        return true;
    }
}

Repository

存储库

package net.jkratz.igdb.repository;

import net.jkratz.igdb.model.ESRBRating;

import org.springframework.data.jpa.repository.JpaRepository;

public interface ESRBRatingRepository extends JpaRepository<ESRBRating, Long> {

}

Model

模型

@Entity
@Table(name = "esrb_rating", schema = "igdb")
@JsonIgnoreProperties(ignoreUnknown = true)
public class ESRBRating implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @NotNull
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id", nullable = false)
    private Long id;

    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "title", nullable = false, length = 255)
    private String title;

    @Size(max = 65535)
    @Column(length = 65535)
    private String description;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "esrbRating")
    private List<Game> games;

    public ESRBRating() {
    }

    public ESRBRating(Long id, String title, String description) {
        this.id = id;
        this.title = title;
        this.description = description;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ESRBRating that = (ESRBRating) o;

        return Objects.equal(this.id, that.id) &&
                Objects.equal(this.title, that.title) &&
                Objects.equal(this.description, that.description);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(id, title, description);
    }

    @Override
    public String toString() {
        return Objects.toStringHelper(this)
                .add("id", id)
                .add("title", title)
                .add("description", description)
                .toString();
    }
}

This controller code works fine, going through the repository directly.

这个控制器代码工作正常，直接通过存储库。

@RestController
@RequestMapping(produces = "application/json", value="/esrbrating")
public class ESRBRatingController {

@Inject
ESRBRatingService esrbRatingService;

@Inject
ESRBRatingRepository esrbRatingRepository;

private Logger logger = LoggerFactory.getLogger(getClass());

/**
 * Returns all ESRB ratings in database
 * 
 * @return List of ESRBRating objects
 * @see ESRBRating
 */
@RequestMapping(value = {"","/"}, method = RequestMethod.GET)
public ResponseEntity<List<ESRBRating>> getESRBRatings() {
    List<ESRBRating> esrbRatings = esrbRatingService.getESRBRatings();
    return new ResponseEntity<>(esrbRatings, HttpStatus.OK);
}

/**
 * Returns a single ESRB rating object if exists, otherwise returns HTTP status code 404
 *
 * @param id ID of the ESRB Rating
 * @return ESRB Rating when found
 * @see ESRBRating
 */
@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<?> getUser(@PathVariable("id") Long id) {
    logger.debug("Attempting to fetch ESRB rating with ID: {}", id);
    ESRBRating esrbRating = esrbRatingRepository.findOne(id);

    if (esrbRating == null) {
        return new ResponseEntity<>("ESRB Rating not found", HttpStatus.NOT_FOUND);
    } else {
        return new ResponseEntity<>(esrbRating, HttpStatus.OK);
    }
}

}

}

UPDATE:

更新：

I followed Randall Harleigh advice and set the reverse collection with @JsonIgnore. However now I am getting an entirely different stack trace. It seems now Hymanson / Spring doesn't know how to serialize ESRBRating. Any tips on this one?

我遵循了 Randall Harleigh 的建议，并使用 @JsonIgnore 设置了反向集合。但是现在我得到了一个完全不同的堆栈跟踪。现在看来 Hymanson / Spring 不知道如何序列化 ESRBRating。关于这个有什么提示吗？

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"]); nested exception is com.fasterxml.Hymanson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"])
    at org.springframework.http.converter.json.AbstractHymanson2HttpMessageConverter.writeInternal(AbstractHymanson2HttpMessageConverter.java:238)
    at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:208)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:158)
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:138)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:781)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:721)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:943)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter.doFilter(DefaultLoginPageGeneratingFilter.java:155)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
Caused by: com.fasterxml.Hymanson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"])
    at com.fasterxml.Hymanson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59)
    at com.fasterxml.Hymanson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:26)
    at com.fasterxml.Hymanson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505)
    at com.fasterxml.Hymanson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
    at com.fasterxml.Hymanson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
    at com.fasterxml.Hymanson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:114)
    at com.fasterxml.Hymanson.databind.ObjectMapper.writeValue(ObjectMapper.java:1887)
    at org.springframework.http.converter.json.AbstractHymanson2HttpMessageConverter.writeInternal(AbstractHymanson2HttpMessageConverter.java:231)
    ... 72 more

Update 2:

更新 2：

I ended up putting @Proxy(lazy = false) on the ESRBRating class and now it works fine. However I'm curious what kind of performance impacts this could have?

我最终将 @Proxy(lazy = false) 放在 ESRBRating 类上，现在它工作正常。但是我很好奇这会产生什么样的性能影响？

@Entity
@Table(name = "esrb_rating", schema = "igdb")
@JsonIgnoreProperties(ignoreUnknown = false)
@Proxy(lazy = false)
public class ESRBRating implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @NotNull
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id", nullable = false)
    private Long id;

    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "title", nullable = false, length = 255)
    private String title;

    @Size(max = 65535)
    @Column(length = 65535)
    private String description;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "esrbRating")
    private List<Game> games;

    public ESRBRating() {
    }

    public ESRBRating(Long id, String title, String description) {
        this.id = id;
        this.title = title;
        this.description = description;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }


    @JsonIgnore
    public List<Game> getGames() {
        return games;
    }

    public void setGames(List<Game> games) {
        this.games = games;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ESRBRating that = (ESRBRating) o;

        return Objects.equal(this.id, that.id) &&
                Objects.equal(this.title, that.title) &&
                Objects.equal(this.description, that.description);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(id, title, description);
    }

    @Override
    public String toString() {
        return Objects.toStringHelper(this)
                .add("id", id)
                .add("title", title)
                .add("description", description)
                .toString();
    }
}

As requested here is the Game class

按照这里的要求是游戏类

@Entity
@Table(name = "game", schema = "igdb",
        indexes = {@Index(name = "idx_game_title", columnList = ("title"), unique = false),
                @Index(name = "idx_game_developer", columnList = ("developer"), unique = false),
                @Index(name = "idx_game_publisher", columnList = ("publisher"), unique = false)})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Game implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @NotNull
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id", nullable = false)
    private Long id;

    @NotNull
    @Size(min = 1, max = 255)
    @Column(name = "title", nullable = false, length = 255)
    private String title;

    @Size(max = 65535)
    @Column(name = "description", length = 65535)
    private String description;

    @Size(max = 255)
    @Column(name = "developer", length = 255)
    private String developer;

    @Size(max = 255)
    @Column(name = "publisher", length = 255)
    private String publisher;

    @NotNull
    @Size(max = 4)
    @Column(name = "players", nullable = false)
    private short players;

    @NotNull
    @Column(name = "cooperative", nullable = false)
    private boolean cooperative;

    @NotNull
    @Column(name = "release_date", nullable = false)
    @Temporal(TemporalType.DATE)
    private Date releaseDate;

    @Size(max = 255)
    @Column(name = "image", length = 255)
    private String image;

    @JoinColumn(name = "esrb_rating_id", referencedColumnName = "id", nullable = false)
    @ManyToOne(optional = false, fetch = FetchType.EAGER)
    private ESRBRating esrbRating;   

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "game")
    private List<GamePlatformMap> gamePlatformMap;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "game")
    private List<GameGenreMap> gameGenreMap;

    public Game() {

    }

    public Game(Long id, String title, String description, String developer,
            String publisher, short players, boolean cooperative,
            Date releaseDate, String image, ESRBRating esrbRating) {
        super();
        this.id = id;
        this.title = title;
        this.description = description;
        this.developer = developer;
        this.publisher = publisher;
        this.players = players;
        this.cooperative = cooperative;
        this.releaseDate = releaseDate;
        this.image = image;
        this.esrbRating = esrbRating;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getDeveloper() {
        return developer;
    }

    public void setDeveloper(String developer) {
        this.developer = developer;
    }

    public String getPublisher() {
        return publisher;
    }

    public void setPublisher(String publisher) {
        this.publisher = publisher;
    }

    public short getPlayers() {
        return players;
    }

    public void setPlayers(short players) {
        this.players = players;
    }

    public boolean isCooperative() {
        return cooperative;
    }

    public void setCooperative(boolean cooperative) {
        this.cooperative = cooperative;
    }

    public Date getReleaseDate() {
        return releaseDate;
    }

    public void setReleaseDate(Date releaseDate) {
        this.releaseDate = releaseDate;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public ESRBRating getEsrbRating() {
        return esrbRating;
    }

    public void setEsrbRating(ESRBRating esrbRating) {
        this.esrbRating = esrbRating;
    }

    @JsonIgnore
    public List<GamePlatformMap> getGamePlatformMap() {
        return gamePlatformMap;
    }

    public void setGamePlatformMap(List<GamePlatformMap> gamePlatformMap) {
        this.gamePlatformMap = gamePlatformMap;
    }

    @JsonIgnore
    public List<GameGenreMap> getGameGenreMap() {
        return gameGenreMap;
    }

    public void setGameGenreMap(List<GameGenreMap> gameGenreMap) {
        this.gameGenreMap = gameGenreMap;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Game that = (Game) o;

        return Objects.equal(this.id, that.id) &&
                Objects.equal(this.title, that.title) &&
                Objects.equal(this.description, that.description) &&
                Objects.equal(this.developer, that.developer) &&
                Objects.equal(this.publisher, that.publisher) &&
                Objects.equal(this.players, that.players) &&
                Objects.equal(this.cooperative, that.cooperative) &&
                Objects.equal(this.releaseDate, that.releaseDate) &&
                Objects.equal(this.image, that.image) &&
                Objects.equal(this.esrbRating, that.esrbRating);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(id, title, description, developer, publisher, players,
                cooperative, releaseDate, image, esrbRating);
    }

    @Override
    public String toString() {
        return Objects.toStringHelper(this)
                .add("id", id)
                .add("title", title)
                .add("description", description)
                .add("developer", developer)
                .add("publisher", publisher)
                .add("players", players)
                .add("cooperative", cooperative)
                .add("releaseDate", releaseDate)
                .add("image", image)
                .add("esrbRating", esrbRating)
                .toString();
    }
}

回答by Randall Harleigh

This typically happens when you are returning an object via @Responsebody (or in your case response body by way of @RestController) and an object is being serialized but has children in a LAZY collection that have not been referenced. By the time you are in your controller there is no longer a transaction active that will facilitate them being fetched (like the one your started in your @Service). You can either make your fetch strategy EAGER, bring in your collections by reference while still in your transaction or make your LAZY collections JSON Transient.

这通常发生在您通过@Responsebody（或在您的情况下通过@RestController 的响应主体）返回一个对象并且一个对象正在被序列化但在 LAZY 集合中具有尚未被引用的子项时。当您在控制器中时，不再有活动的事务可以促进它们被获取（就像您在 @Service 中启动的那个）。您可以使您的 fetch 策略 EAGER，在您的交易中通过引用引入您的集合，或者使您的 LAZY 集合 JSON Transient。

回答by Amit Nain

First download Hymanson-datatype-hibernate4-2.2.3.jar or higher version according to Hymanson-core version. Then use this code in config file and you can use fetch strategy LAZY without any error.

首先根据Hymanson-core版本下载Hymanson-datatype-hibernate4-2.2.3.jar或更高版本。然后在配置文件中使用此代码，您可以使用 LAZY 获取策略而不会出现任何错误。

import com.fasterxml.Hymanson.databind.ObjectMapper;
import com.fasterxml.Hymanson.datatype.hibernate4.Hibernate4Module;


public class ApplicationConfig extends WebMvcConfigurerAdapter
{
public MappingHymanson2HttpMessageConverter HymansonMessageConverter(){
    MappingHymanson2HttpMessageConverter messageConverter = new  MappingHymanson2HttpMessageConverter();

    ObjectMapper mapper = new ObjectMapper();
    //Registering Hibernate4Module to support lazy objects
    mapper.registerModule(new Hibernate4Module());

    messageConverter.setObjectMapper(mapper);
    return messageConverter;

}

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    //Here we add our custom-configured HttpMessageConverter
    converters.add(HymansonMessageConverter());
    super.configureMessageConverters(converters);
}

回答by Fatos Morina

@JsonIgnore annotation might solve your problem, but it causes that particular field that you initially set as FetchType.LAZY to be completely ignored. A better alternative is given here https://stackoverflow.com/a/21760361/3609067

@JsonIgnore 注释可能会解决您的问题，但它会导致您最初设置为 FetchType.LAZY 的特定字段被完全忽略。这里给出了一个更好的选择 https://stackoverflow.com/a/21760361/3609067