java-8 - JPA 2.1 @SqlResultSetMapping 将内部类绑定(bind)到目标类

Question

是否可以将内部类映射到 targetclass ，如果可能的话，它是怎么做的？我是新手@SqlResultSetMapping功能:

@SqlResultSetMapping(
        name = "EventSurveysMapping",
        classes = {
                @ConstructorResult(
                        targetClass = Survey.class,
                        columns = {
                                @ColumnResult(name = "surveyid", type = Long.class),
                        })
        })

所以 targetClass Survey.class拥有:

public class Survey {
    private Long surveyid;
    private List<SurveyQuestion> surveyquestions;
// constructor with mapped fields
}

我将如何映射 List<SurveyQuestion> field ？

调查问题:

public class SurveyQuestion {
    private Long surveyquestionid;
    private String surveyquestion;
    private List<String> surveyanswers;
}

而且，和非常相似。我将如何映射 List<String> ?

尝试映射到 List.class 时出现异常:

@SqlResultSetMapping(
        name = "EventPollsMapping",
        classes = {
                @ConstructorResult(
                        targetClass = Poll.class,
                        columns = {
                                @ColumnResult(name="pollid", type = Long.class),
                                @ColumnResult(name="questionid", type = Long.class),
                                @ColumnResult(name="pollquestion", type = String.class),
                                @ColumnResult(name="pollanswers", type = List.class) // this mapping is the cause of the exception
                        })
        })

异常(exception):

org.eclipse.persistence.exceptions.ConversionException Exception Description: The object [It is Primary ID, It is unique ID], of class [class java.lang.String], could not be converted to [interface java.util.List]

轮询:

@XmlRootElement
@XmlType (propOrder={"pollid",
"pollquestionid",
"pollquestion",
"pollanswers"
})
public class Poll {
    private Long pollid;
    private Long pollquestionid;
    private String pollquestion;
    private List<String> pollanswers;


    public Poll(){}

    public Poll(Long pollid, Long pollquestionid, String pollquestion, List<String> pollanswers) {
        super();
        this.pollid = pollid;
        this.pollquestionid = pollquestionid;
        this.pollquestion = pollquestion;
        this.pollanswers = pollanswers;
    }

// setters & getters 
}

Answer 1

以我的经验，当我必须映射一个集合时，最后我做了这样的事情:

@OneToMany
private Set<SurveyQuestion> surveyanswers;

如果您使用的是支持基本类型集合的 JPA 提供程序的扩展，那么所有这些。 (例如，Hibernate 有 @CollectionOfElements 注释)。