我正在构建一个使用和返回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获取ESRBRating ID时，它可以正常工作。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，而不是直接通过Spring Data JPA存储库时会发生这种情况吗？我该如何解决这个问题？
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.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:466)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
... 76 more
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);
}
}
}
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;
}
}
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> {
}
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();
}
}
此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);
}
}
}
更新：
我跟随了Randall Harleigh的建议并用@JsonIgnore设置了反向收集。但是现在我得到一个完全不同的堆栈跟踪。现在看来Jackson / Spring不知道如何序列化ESRBRating。关于这个的任何提示？
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_$$_jvstb5c_0["handler"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: net.jkratz.igdb.model.ESRBRating_$$_jvstb5c_0["handler"])
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.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.jackson.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.jackson.databind.ser.impl.UnknownSerializer.failForEmpty(UnknownSerializer.java:59)
at com.fasterxml.jackson.databind.ser.impl.UnknownSerializer.serialize(UnknownSerializer.java:26)
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505)
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:114)
at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1887)
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:231)
... 72 more
更新2：
我最终在ESRBRating类上放了@Proxy（lazy = false），现在它工作正常。但是我很好奇这可能带来什么样的性能影响？
@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();
}
}
这里要求的是游戏类
@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();
}
}
答案 0 :(得分：31)
这通常发生在您通过@Responsebody返回对象时（或者通过@RestController返回您的案例响应体）并且对象被序列化但是LAZY集合中的子项尚未被引用。当您在控制器中时，不再有活动的事务将有助于它们被提取（就像您在@Service中启动的那个）。您可以制作获取策略EAGER，在您的交易中通过引用引入您的馆藏，或者制作您的LAZY集合JSON Transient。
答案 1 :(得分：7)
首先根据jackson-core版本下载jackson-datatype-hibernate4-2.2.3.jar或更高版本。然后在配置文件中使用此代码，您可以使用获取策略LAZY而不会出现任何错误。
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.hibernate4.Hibernate4Module;
public class ApplicationConfig extends WebMvcConfigurerAdapter
{
public MappingJackson2HttpMessageConverter jacksonMessageConverter(){
MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();
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(jacksonMessageConverter());
super.configureMessageConverters(converters);
}
答案 2 :(得分：2)
@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。这里给出了更好的结果 https://stackoverflow.com/a/21760361/3609067
答案 3 :(得分：0)
通过添加到gradle.build解决了Spring Boot @Bean
public Module datatypeHibernateModule() {
return new Hibernate5Module();
}
：
实现'com.fasterxml.jackson.datatype：jackson-datatype-hibernate5：2.11.3'
再声明一个bean：
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答案 4 :(得分：0)
我遇到了同样的错误，但没有任何答案对我有帮助。
问题似乎出在jpa.open-in-view=false。我已将其删除，现在一切正常。