@ElementCollection setField 00942: ORA-00942

Question

我有两个java类，其中一个类以@ElementCollection的列表形式包含另一个类。当我试图设置该列表时，会发生以下错误：

Local Exception Stack: 
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.1.3.v20110304-r9073): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: ORA-00942: table or view does not exist

Error Code: 942
Call: SELECT t0.VERSIONS FROM MainProcess_VERSIONS t0 WHERE (t0.MainProcess_SUBJECT_ID = ?)
bind => [#id]
Query: DirectReadQuery(name="versions" sql="SELECT t0.VERSIONS 
FROM MainProcess_VERSIONS t0 WHERE (t0.MainProcess_SUBJECT_ID = ?)")
at org.eclipse.persistence.exceptions.DatabaseException.sqlException(DatabaseException.java:333)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.basicExecuteCall(DatabaseAccessor.java:683)
at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeCall(DatabaseAccessor.java:526)
.
.
.
at ...Editor.MAINPROCESS._persistence_propertyChange(MAINPROCESS.java)
at ...Editor.MAINPROCESS._persistence_set_versions(MAINPROCESS.java)
at ...MAINPROCESS.setVersions(MAINPROCESS.java:79)
at ...DataModel.fillSubprocessSubject(DataModel.java:643)
at ...DataModel.load(DataModel.java:321)

如果删除@ElementCollection，则会得到以下错误

Error Code: 942
Call: 
SELECT t1.ACT_VERSION, t1.SUBJECT_ID, t1.ACT_VERSION_REMARK,
  t1.ACT_VALID_TO, t1.ACT_VERSION_ACCEPTED, t1.NORMALRETURNVALUES, t1.ACT_VALID_FROM 
FROM MAINPROCESS_MAINPROCESSVERSION t0, MAINPROCESSVERSION t1
WHERE ((t0.MainProcess_SUBJECT_ID = ?) AND ((t1.SUBJECT_ID = t0.SUBJECT_ID) 
AND (t1.ACT_VERSION = t0.ACT_VERSION)))
    bind => [#id]

这是我的课，

MainProcess：

@Entity
public class MainProcess implements Serializable {

  @Id
  @Column(name = "SUBJECT_ID", nullable = false)
  private Long subjectId;
  
  ...other columns

  @ElementCollection
  private List<MainProcessVersion> versions = new ArrayList<MainProcessVersion>();

  public MainProcess() {
  }

  public void setVersions(List<MainProcessVersion> versions) {
    this.versions = versions;
  }

  public List<MainProcessVersion> getVersions() {
    return versions;
  }

  other getters and setters...
}

MainProcessVersion：

@Entity
@IdClass(MainProcessVersionPK.class)
public class MainProcessVersion implements Serializable {

  @Id
  @Column(name = "SUBJECT_ID", nullable = false)
  @XmlTransient
  private Long subjectId;

  @Id
  @Column(name = "ACT_VERSION")
  private Long actVersion;

  ...other columns

  private List<String> normalReturnValues;

  public MainProcessVersion() {
  }

  getters and setters...

}

以及发生错误的函数：

private MainProcess fillSubprocessSubject(Long Id) {
    MainProcess p = someFacade.getProcess(Id);
    List<MainProcessVersion> versions = someFacade.getProcessVersions(Id);
    p.setVersions(versions); //error is here
    return p;
}

提前感谢您的帮助。

Answer 1

我设法解决了我的问题。最重要的是理解@ElementCollection和@OneToMany注释之间的区别。我无法更好地像this那样解释。

所以问题是我的MainProcessVersion.java是用@Entity注释的，因此我不能在MainProcess.java中添加@ElementCollection注释。

 @ElementCollection //One cannot use this annotation because MainProcessVersion is an entity.
 private List<MainProcessVersion> versions = new ArrayList<MainProcessVersion>();

但是我需要实体，所以我创建的resultRow类与我的实体类是相同的，除了注释。在查询选择之后，我将结果转换为新的resultRow类，并可以在MainProcess.java中设置该列表。

我的resultRow课程：

public class MainProcessVersionResultRow implements Serializable {
    
    private Long subjectId;
    ...other code
}

我以前的MainProcess课

 @Entity
public class MainProcess implements Serializable {

    @Id
    @Column(name = "SUBJECT_ID", nullable = false)
    private Long subjectId;

    ...other columns
    
    //without @ElementCollection and the new resultRow object type
    private List<MainProcessVersionResultRow> versions = new ArrayList<MainProcessVersionResultRow>();

    public MainProcess() {
    }

    ...getters. setters
}

然后，我将我的实体“转换”到resultRow类：

private MainProcess fillSubprocessSubject(Long subjectId) {
        MainProcess p =
            someFacade.getSubprocessSubject(subjectId);
        List<MainProcessVersion> versions = someFacade.getProcessVersions(subjectId);
        List<MainProcessVersionResultRow> versionResultRows = new ArrayList<MainProcessVersionResultRow>();

        for (MainProcessVersion vs : versions) {
            MainProcessVersionResultRow versionSingleResultRow = new MainProcessVersionResultRow(vs);
            versionSingleResultRow.setNormalReturnValues(processReturnValues(p.getSubjectId(), vs.getActVersion()));
            versionResultRows.add(versionSingleResultRow);
        }

        p.setVersions(versionResultRows); //does not throw an error any more
        return p;
    }

因此，结论：不要在具有@Entity注释的类上使用@ElementCollection。