Question

我正在使用Eclipselink，我有以下JPQL查询：

SELECT NEW javax.faces.model.SelectItem((java.lang.Object) s.id, s.description) FROM Status s WHERE s.active = TRUE

需要s.id之前的广告投放，因为SelectItem的构造函数需要Object和String，但Status.id是long

但是，执行此查询时，我得到以下异常：

Caused by: Exception [EclipseLink-8024] (Eclipse Persistence Services - 2.0.1.v20100213-r6600): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Syntax error parsing the query [SELECT NEW javax.faces.model.SelectItem((java.lang.Object) s.id, s.description) FROM Status WHERE s.active = TRUE], line 1, column 59: syntax error at [s].
Internal Exception: MismatchedTokenException(78!=82)
    at org.eclipse.persistence.exceptions.JPQLException.syntaxErrorAt(JPQLException.java:362)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.handleRecognitionException(JPQLParser.java:304)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.addError(JPQLParser.java:245)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.reportError(JPQLParser.java:362)
    at org.eclipse.persistence.internal.libraries.antlr.runtime.BaseRecognizer.recoverFromMismatchedElement(Unknown Source)
    at org.eclipse.persistence.internal.libraries.antlr.runtime.BaseRecognizer.recoverFromMismatchedToken(Unknown Source)
    at org.eclipse.persistence.internal.libraries.antlr.runtime.BaseRecognizer.mismatch(Unknown Source)
    at org.eclipse.persistence.internal.libraries.antlr.runtime.BaseRecognizer.match(Unknown Source)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.constructorExpression(JPQLParser.java:2635)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.selectExpression(JPQLParser.java:2045)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.selectItem(JPQLParser.java:1351)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.selectClause(JPQLParser.java:1266)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.selectStatement(JPQLParser.java:352)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.antlr.JPQLParser.document(JPQLParser.java:276)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.parse(JPQLParser.java:133)
    at org.eclipse.persistence.internal.jpa.parsing.jpql.JPQLParser.buildParseTree(JPQLParser.java:94)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:198)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:173)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:125)
    at org.eclipse.persistence.internal.jpa.EJBQueryImpl.<init>(EJBQueryImpl.java:109)
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.createQuery(EntityManagerImpl.java:1326)
    ... 51 more
Caused by: MismatchedTokenException(78!=82)
    ... 66 more

如何在没有例外的情况下将s.id投射到java.lang.Object？

Answer 1

我认为不可能。

顺便说一下，混合GUI层（SelectItem类）和持久层（JPA）是一种不好的做法。我将使用适当的构造函数（long，String）创建单独的StatusDTO类，然后手动将其映射到SelectItem。

通过这种方式，您可以独立于GUI更改进行数据库层更改。例如，如果数据库中的某些列将更改其类型，则不会影响您的GUI层，因为您可以在一个地方处理它--DTO类。否则，您必须遍历所有在SelectItem等与DB查询之间存在依赖关系的地方。

使用NEW时在JPQL中进行转换

1 个答案: