Question

我的用户DTO中有以下映射来存储Map用户属性：

@Entity(name = "User")
public class User{

    @Id
    @Column(name = "Id")
    private long userId;

    @OneToMany
    @JoinColumn(name = "properties")
    private Map<Long, Property> properties= new LinkedHashMap<Long, LkpAIT>();

}

@Entity(name = "Property")
public class Property{

    @Id
    @Column(name = "Id")
    private long propertyId;

    @Column(name = "Name")
    private String propertyName;

}

以下@Controller方法

@RequestMapping(value = "/getUser", produces = "application/json", method = RequestMethod.GET)
public @ResponseBody Page<LkpFeed> getLookupFeeds(Model model) {
    page = 1;
    Page<User> users = userRepo.getUsers(new PageRequest(page, 100)); //returns 100 users
    return feeds;
}

@Controller方法执行正常（找到所有用户）但是当return语句执行时，我收到以下错误：

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.myapp.dto.Properties.properties, could not initialize proxy - no Session
    org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:575)
    org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:214)
    org.hibernate.collection.internal.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:155)
    org.hibernate.collection.internal.PersistentMap.isEmpty(PersistentMap.java:145)
    com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:399)
    com.fasterxml.jackson.databind.ser.std.MapSerializer.serialize(MapSerializer.java:27)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:505)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:639)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:152)
    com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:100)

基于异常我的属性字段是导致错误的原因。我已尝试使用fetchTypes和PersistenceContexts但我目前处于亏损状态。有什么想法吗？

Answer 1

你可以做几件事

在@OneToMany

中添加提取热切

@Entity(name = "User")
public class User{

    @Id
    @Column(name = "Id")
    private long userId;

    @OneToMany(fetch=FetchType.EAGER)
    @JoinColumn(name = "properties")
    private Map<Long, Property> properties= new LinkedHashMap<Long, LkpAIT>();

}

或者，如果您只想列出用户，则不希望在返回的JSON中使用“属性”。您可以为@JsonIgnore

添加properties

@Entity(name = "User")
public class User{

    @Id
    @Column(name = "Id")
    private long userId;

    @JsonIgnore
    @OneToMany
    @JoinColumn(name = "properties")
    private Map<Long, Property> properties= new LinkedHashMap<Long, LkpAIT>();

}

@OneToMany列返回LazyInitializationException - Spring

1 个答案: