JPQL 查询返回 NullPointerException答案

【问题标题】：JPQL query returns NullPointerExceptionJPQL 查询返回 NullPointerException
【发布时间】：2019-03-07 21:03:20
【问题描述】：

我的存储库界面中有以下 JPQL 查询：

@Override
@Query(value = "SELECT mainFoo FROM MainFooEntity mainFoo JOIN FETCH mainFoo.nestedFoo.bar b WHERE b.value LIKE %:searchedFoo%")
Page<MainFooEntity> findByFoo(@Param("searchedFoo") String searchedFoo, Pageable pageable);

这是我的 MainFooEntity：

@Entity
@Table
public class MainFooEntity {
   @Id
   @GeneratedValue(strategy = GenerationType.SEQUENCE)
   private Long id;

   @Embedded
   private NestedFooEntity nestedFoo;

   // ...
}

可嵌入的NestedFooEntity 类：

@Embeddable
public class NestedFooEntity {

    @Type(type = "com.my.BarType")
    @Column(name = "bar")
    private BarType bar;

    // ...
}

还有我的自定义 BarType 类：

@lombok.Value
public class BarType implements Comparable<BarType>{
    String value;

    public BarType(String value) {
        this.value = value;
    }
}

当我调用上面的存储库方法时，出现以下错误：

Caused by: java.lang.IllegalArgumentException: Validation failed for query for method public abstract org.springframework.data.domain.Page com.my.FooRepository.findByFoo(java.lang.String,org.springframework.data.domain.Pageable)!
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.validateQuery(SimpleJpaQuery.java:93)
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.<init>(SimpleJpaQuery.java:63)
    at org.springframework.data.jpa.repository.query.JpaQueryFactory.fromMethodWithQueryString(JpaQueryFactory.java:76)
    at org.springframework.data.jpa.repository.query.JpaQueryFactory.fromQueryAnnotation(JpaQueryFactory.java:56)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$DeclaredQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:139)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$CreateIfNotFoundQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:206)
    at org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy$AbstractQueryLookupStrategy.resolveQuery(JpaQueryLookupStrategy.java:79)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lookupQuery(RepositoryFactorySupport.java:565)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$mapMethodsToQuery$1(RepositoryFactorySupport.java:558)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Iterator.forEachRemaining(Iterator.java:116)
    at java.util.Collections$UnmodifiableCollection$1.forEachRemaining(Collections.java:1049)
    at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.mapMethodsToQuery(RepositoryFactorySupport.java:560)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.lambda$new$0(RepositoryFactorySupport.java:550)
    at java.util.Optional.map(Optional.java:215)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.<init>(RepositoryFactorySupport.java:550)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport.getRepository(RepositoryFactorySupport.java:323)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.lambda$afterPropertiesSet$4(RepositoryFactoryBeanSupport.java:290)
    at org.springframework.data.util.Lazy.getNullable(Lazy.java:141)
    at org.springframework.data.util.Lazy.get(Lazy.java:63)
    at org.springframework.data.repository.core.support.RepositoryFactoryBeanSupport.afterPropertiesSet(RepositoryFactoryBeanSupport.java:293)
    at org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean.afterPropertiesSet(JpaRepositoryFactoryBean.java:102)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1758)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1695)
    ... 55 more
Caused by: java.lang.NullPointerException
    at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:424)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3931)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3717)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3595)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:720)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:576)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:313)
    at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:261)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:266)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:189)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:141)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115)
    at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:77)
    at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:153)
    at org.hibernate.internal.AbstractSharedSessionContract.getQueryPlan(AbstractSharedSessionContract.java:553)
    at org.hibernate.internal.AbstractSharedSessionContract.createQuery(AbstractSharedSessionContract.java:662)
    at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:350)
    at com.sun.proxy.$Proxy190.createQuery(Unknown Source)
    at org.springframework.data.jpa.repository.query.SimpleJpaQuery.validateQuery(SimpleJpaQuery.java:87)
    ... 84 more

你知道我做错了什么吗？感谢您的建议。

【问题讨论】：

Hibernate throws NullPointerException from HqlSqlWalker的可能重复

标签： hibernate jpa spring-data-jpa hql jpql

【解决方案1】：

根据 JPA 2.1 规范（强调我的），您的 Join Fetch 子句是不合法的：

FETCH JOIN 子句右侧引用的关联必须是从作为查询结果返回的实体或可嵌入对象引用的关联或元素集合。 不允许为 FETCH JOIN 子句右侧引用的对象指定标识变量，因此对隐式获取的实体或元素的引用不能出现在查询的其他位置。

因此您需要将查询更改为：

SELECT mainFoo 
FROM MainFooEntity mainFoo 
JOIN FETCH mainFoo.nestedFoo.bar 
WHERE mainFoo.nestedFoo.bar.value LIKE %:searchedFoo%

您也可以考虑向 Hibernate 提出问题以改进错误消息，因为到处乱扔 NPE 有点粗鲁，不是吗？

【讨论】：

【解决方案2】：

问题是路径上的一个类 (NestedFooEntity)不是实体，它是一个可嵌入的对象。所以，它不能加入。

所以，你可以试试：

@Query(value = "SELECT mainFoo FROM MainFooEntity mainFoo 
    JOIN FETCH mainFoo.bar
    JOIN mainFoo.bar bar
    JOIN bar.b b 
    WHERE b.value LIKE %:searchedFoo% ")

【讨论】：