java - 为什么在 JPA findAll() 方法检索的对象中，我无法访问映射为关系的字段？
问题描述
我正在使用 Spring Data JPA 开发 Spring Boot 项目，但在尝试检索数据时遇到以下问题。
我有这个User类映射一个portal_user数据库表：
@Entity
@Table(name = "portal_user")
@Getter
@Setter
public class User implements Serializable {
private static final long serialVersionUID = 5062673109048808267L;
@Id
@Column(name = "id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
@Column(name = "first_name")
private String firstName;
@Column(name = "middle_name")
private String middleName;
@Column(name = "surname")
private String surname;
@Column(name = "sex")
private char sex;
@Column(name = "birthdate")
private Date birthdate;
@Column(name = "tex_code")
private String taxCode;
@Column(name = "e_mail")
private String eMail;
@Column(name = "contact_number")
private String contactNumber;
@Temporal(TemporalType.DATE)
@Column(name = "created_at")
private Date createdAt;
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "user", orphanRemoval = true)
@JsonManagedReference
private Set<Address> addressesList = new HashSet<>();
//@OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
//@JsonManagedReference
//private Set<User_UserType> userToUserTypeAssociation = new HashSet<>();
@ManyToMany(cascade = { CascadeType.MERGE })
@JoinTable(
name = "portal_user_user_type",
joinColumns = { @JoinColumn(name = "portal_user_id_fk") },
inverseJoinColumns = { @JoinColumn(name = "user_type_id_fk") }
)
Set<UserType> userTypes;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(String firstName, String middleName, String surname, char sex, Date birthdate, String taxCode,
String eMail, String contactNumber, Date createdAt) {
super();
this.firstName = firstName;
this.middleName = middleName;
this.surname = surname;
this.sex = sex;
this.birthdate = birthdate;
this.taxCode = taxCode;
this.eMail = eMail;
this.contactNumber = contactNumber;
this.createdAt = createdAt;
}
}
正如您在这个实体类中看到的那样，存在一些关系，例如这个@OnetoMany关系：
@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "user", orphanRemoval = true)
@JsonManagedReference
private Set<Address> addressesList = new HashSet<>();
这是我的地址实体类映射我的数据库上的地址表：
@Entity
@Table(name = "address")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class Address implements Serializable {
private static final long serialVersionUID = 6956974379644960088L;
@Id
@Column(name = "id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
@Column(name = "country")
private String country;
@Column(name = "province")
private String province;
@Column(name = "zip_code")
private String zipCode;
@Column(name = "street")
private String street;
@Column(name = "notes")
private String notes;
//@Column(name = "fk_user_id")
//private int fkUserId;
@ManyToOne
@EqualsAndHashCode.Exclude // Needed by Lombock in "Many To One" relathionship to avoid error
@JoinColumn(name = "fk_user_id", referencedColumnName = "id")
@JsonBackReference
private User user;
public Address(String country, String province, String zipCode, String street, String notes, User user) {
super();
this.country = country;
this.province = province;
this.zipCode = zipCode;
this.street = street;
this.notes = notes;
this.user = user;
}
}
我创建了这个单元测试方法来测试将所有记录检索到我的portal_user表中（以及来自关系的信息）：
@Test
@Order(2)
public void RetrieveAllUsers() {
List<User> usersList = this.userRepository.findAll();
System.out.println(usersList.get(0).getAddressesList());
System.out.println(usersList.get(0).getUserTypes());
assertTrue(true);
}
findAll()方法似乎有效并且检索了列表，但是使用调试器我看不到表示关系的两个字段的值，这就是我在调试器的“表达式”选项卡中所包含的内容。
usersList (id=180)
[0] User (id=193)
addressesList PersistentSet (id=199)
Error Exception occurred: com.sun.jdi.InvocationException: Exception occurred in target VM occurred invoking method..
birthdate Timestamp (id=204)
contactNumber 329123456" (id=208)
createdAt Date (id=213)
eMail xxx@gmail.com" (id=215)
firstName Luca" (id=216)
id 25
middleName null
sex M
surname Verdi" (id=217)
taxCode XXX" (id=218)
userTypes PersistentSet (id=220)
Error Exception occurred: com.sun.jdi.InvocationException: Exception occurred in target VM occurred invoking method..
[1] User (id=196)
[2] User (id=197)
Add new expression
如您所见，代表我的关系的addressesList和userTypes字段的值类似于：
Error Exception occurred: com.sun.jdi.InvocationException: Exception occurred in target VM occurred invoking method..
正如您在前面的单元测试方法代码中看到的那样，我尝试通过以下方式访问它：
usersList.get(0).getAddressesList())
但是当执行此代码时，我得到了这个异常：
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.easydefi.users.entity.User.addressesList, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:606)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:218)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149)
at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:327)
at java.base/java.lang.String.valueOf(String.java:3365)
at java.base/java.io.PrintStream.println(PrintStream.java:1047)
at com.easydefi.users.tests.RepositoryTests.UserRepositoryTest.RetrieveAllUsers(UserRepositoryTest.java:86)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:567)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:84)
at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:98)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:40)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:529)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:756)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:452)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
问题是什么？我错过了什么？我该如何尝试解决此问题？
解决方案
您正试图在打开的 Hibernate 会话的上下文之外访问延迟加载的对象。为避免此错误，您有一些选择，其中两个：
1. 使用 FetchType.EAGER 策略
@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "user", orphanRemoval = true)
@JsonManagedReference
private Set<Address> addressesList = new HashSet<>();
2.使用Join Fetching
SELECT u FROM User u JOIN FETCH u.adressesList
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