所以我有這個問題，我傳遞給我的服務層函式的引數無論如何都是空的。我得到的錯誤是由以下原因引起的：java.lang.IllegalArgumentException：給定的 id 不能為空！這恰好發生在服務層的 node.get(id) 中，因為該節點為空。
這就是我的應用程式的樣子：
節點類
@Entity
@Data
public class Node {
@Id
@GeneratedValue(strategy = IDENTITY)
private Long id;
private int depth;
private double value;
@Column(unique=true)
private String name;
@ManyToOne //add column definitions as needed
@JoinColumn(name="parent_id")
private Node parent; //each Domain with parent==null is a root domain, all others are subdomains
@OneToMany(mappedBy = "parent",cascade = {CascadeType.REMOVE,CascadeType.PERSIST}) //add column definitions as needed
private List<Node> children;
public Node(final Node parent) {
if(parent==null) throw new IllegalArgumentException("parent required");
this.parent = parent;
this.children = new ArrayList<>();
if (parent==null) {
this.depth=0;
}
else {
this.depth = (parent.getDepth() 1);
}
registerInParentsChilds();
}
public Node() {
this.children = new ArrayList<>();
if (parent==null) {
this.depth=0;
}
else {
this.depth = (parent.getDepth() 1);
}
}
/** Register this domain in the child list of its parent. */
private void registerInParentsChilds() {
this.parent.children.add(this);
}
public List<Node> getChildren() {
return this.children;
}
public void move(final Node newParent) {
try {
this.parent.children.remove(this);
this.parent = newParent;
registerInParentsChilds();
}
catch (Exception e) {
System.out.println(e.getMessage());
}
}
public static Node createRoot() {
return new Node();
}
}
節點存盤庫：
public interface NodeRepository extends JpaRepository<Node, Long> {
Optional<Node> findById(Long id);
}
節點服務：
public interface NodeService {
Node saveNode(Node node);
}
節點服務實作：
@Service @RequiredArgsConstructor @Transactional @Slf4j
public class NodeServiceImpl implements NodeService{
@Autowired
private NodeRepository nodeRepository;
@Override
public Node saveNode(Node node) {
log.info("saving new node {} to DB", node);
Optional<Node> existing_node = nodeRepository.findById(node.getId());
if (existing_node.get()!=null) {
log.info("node already exists");
return null;
} else {
log.info("node saved");
return nodeRepository.save(node);
}
}
}
主應用
@Bean
CommandLineRunner run_again(NodeService nodeService) { //this runs after the app is initialized, so no need for
//manual input
return args -> {
Node root;
root = Node.createRoot();
nodeService.saveNode(root);
System.out.println("root created");
nodeService.saveNode(new Node(root));
System.out.println("a created");
Node b = new Node(root);
nodeService.saveNode(b);
System.out.println("b created");
Node c = new Node();
nodeService.saveNode(c);
System.out.println("c created");
};
}
這是我的錯誤堆疊（就像我說我確切知道問題出在哪里，但我無法修復它）：
java.lang.IllegalStateException: Failed to execute CommandLineRunner
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:772) ~[spring-boot-2.6.3.jar:2.6.3]
at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:753) ~[spring-boot-2.6.3.jar:2.6.3]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:309) ~[spring-boot-2.6.3.jar:2.6.3]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1303) ~[spring-boot-2.6.3.jar:2.6.3]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1292) ~[spring-boot-2.6.3.jar:2.6.3]
at com.example.app.AppApplication.main(AppApplication.java:38) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.6.3.jar:2.6.3]
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: The given id must not be null!; nested exception is java.lang.IllegalArgumentException: The given id must not be null!
at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:374) ~[spring-orm-5.3.15.jar:5.3.15]
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:235) ~[spring-orm-5.3.15.jar:5.3.15]
at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:551) ~[spring-orm-5.3.15.jar:5.3.15]
at org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:61) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:242) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:152) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:174) ~[spring-data-jpa-2.6.1.jar:2.6.1]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:97) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:215) ~[spring-aop-5.3.15.jar:5.3.15]
at jdk.proxy4/jdk.proxy4.$Proxy113.findById(Unknown Source) ~[na:na]
at com.example.app.service.NodeServiceImpl.saveNode(NodeServiceImpl.java:70) ~[classes/:na]
at com.example.app.service.NodeServiceImpl$$FastClassBySpringCGLIB$$b1b25c7c.invoke(<generated>) ~[classes/:na]
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:783) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:753) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:698) ~[spring-aop-5.3.15.jar:5.3.15]
at com.example.app.service.NodeServiceImpl$$EnhancerBySpringCGLIB$$3d60cf81.saveNode(<generated>) ~[classes/:na]
at com.example.app.AppApplication.lambda$run_again$1(AppApplication.java:93) ~[classes/:na]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:769) ~[spring-boot-2.6.3.jar:2.6.3]
... 10 common frames omitted
Caused by: java.lang.IllegalArgumentException: The given id must not be null!
at org.springframework.util.Assert.notNull(Assert.java:201) ~[spring-core-5.3.15.jar:5.3.15]
at org.springframework.data.jpa.repository.support.SimpleJpaRepository.findById(SimpleJpaRepository.java:301) ~[spring-data-jpa-2.6.1.jar:2.6.1]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:568) ~[na:na]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0(RepositoryMethodInvoker.java:289) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker.doInvoke(RepositoryMethodInvoker.java:137) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.RepositoryMethodInvoker.invoke(RepositoryMethodInvoker.java:121) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:529) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:285) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:639) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.doInvoke(QueryExecutorMethodInterceptor.java:163) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.data.repository.core.support.QueryExecutorMethodInterceptor.invoke(QueryExecutorMethodInterceptor.java:138) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:80) ~[spring-data-commons-2.6.1.jar:2.6.1]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:123) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:388) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:119) ~[spring-tx-5.3.15.jar:5.3.15]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.3.15.jar:5.3.15]
at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:137) ~[spring-tx-5.3.15.jar:5.3.15]
... 32 common frames omitted
2022-03-08 20:56:00.626 INFO 12604 --- [ restartedMain] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2022-03-08 20:56:00.630 INFO 12604 --- [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown initiated...
2022-03-08 20:56:00.634 INFO 12604 --- [ restartedMain] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Shutdown completed.
Process finished with exit code 0
uj5u.com熱心網友回復：
物件節點不為空。如果是，您將在部分 node.getId() 中收到 NullPointerException。什么是 null，是確切的 id。因為您還沒有保存節點，因此沒有為它生成 id，它仍然為空。
當您使用@GeneratedValue(strategy = IDENTITY) 配置欄位時，該值將在保存程序中在資料庫中創建，因此在保存物件之前該值仍然為空。這意味著您無法通過其 id 檢查類似物件的存在。您需要檢查其他欄位。
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