JPA查询，ArgumentException

Question

我试图使用一个使用以下查询的结果类来查询两个数据库表：

public List<UserStatus> getUserStatus(String username) {
   String qlString = 
           "SELECT NEW no.uia.slit.ejb.UserStatus(file.filename, file.uploadTime, mod.title, mod.dueAt) "
           + "FROM DownloadableFile file, Module mod"
           + "where file.moduleId = mod.id";
   TypedQuery<UserStatus> query = em.createQuery(qlString, UserStatus.class);
   return query.getResultList();

}

运行此操作将得到以下错误：

Caused by: <openjpa-2.3.0-nonfinal-1540826-r422266:1542644 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: Encountered "mod ." at character 71, but expected: ["(", "+", "-", ":", "?", "ABS", "AVG", "CASE", "COALESCE", "CONCAT", "COUNT", "CURRENT_DATE", "CURRENT_TIME", "CURRENT_TIMESTAMP", "ENTRY", "INDEX", "KEY", "LENGTH", "LOCATE", "LOWER", "MAX", "MIN", "MOD", "NULLIF", "SIZE", "SQRT", "SUBSTRING", "SUM", "TRIM", "TYPE", "UPPER", "VALUE", <BOOLEAN_LITERAL>, <DATE_LITERAL>, <DECIMAL_LITERAL>, <IDENTIFIER>, <INTEGER_LITERAL>, <STRING_LITERAL2>, <STRING_LITERAL>, <TIMESTAMP_LITERAL>, <TIME_LITERAL>].

我的成绩如下：

public class UserStatus {

private String title;
private Date dueAt;
private String filename;
private Timestamp uploadTime;
public UserStatus(){
    super();
}
public UserStatus(String filename, Timestamp uploadTime, String title, Date dueAt) {
    this.filename = filename;
    this.uploadTime = uploadTime;
    this.title = title;
    this.dueAt = dueAt;
}

public void setTitle(String title) {
    this.title = title;
}

public String getTitle() {
    return title;
}

public void setDueAt(Date dueAt) {
    this.dueAt = dueAt;
}
public Date getDueAt() {
    return dueAt;
}

public void setFileName(String filename) {
    this.filename = filename;
}

public String getFileName() {
    return filename;
}

public void setUploadTime(Timestamp uploadTime) {
    this.uploadTime = uploadTime;
}

public Timestamp getUploadTime() {
    return uploadTime;
}

}

我用我找到的一个例子来进行查询，我不知道哪里出了问题，我知道它写着"mod“。是错的，但为什么。

编辑：构造函数，这是我使用的示例。

Answer 1

"MOD“是JPQL语言使用的保留关键字，因此您不能将它用于变量名称。选一些不在名单上的其他名字

Answer 2

mod (导管化)是sql中的一个保留字，将其更改为module，它应该可以工作。