JPA查询，ArgumentException

Question

我正在尝试使用带有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();

}

运行此操作我收到以下错误：

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>].

我的结果类如下：

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;
}

}

我使用了一个我发现的例子来进行查询，我无法弄清楚出了什么问题，我知道它说的是＃34; mod。 ＆＃34;是错的，但为什么。

编辑：https://blogs.oracle.com/adf/entry/ejb_dc_using_jpql_constructor这是我使用的例子。

Answer 1

＆＃34; MOD＆＃34;是JPQL语言使用的保留关键字，因此您无法将其用于变量名称。选择不在该列表中的其他名称

Answer 2

mod（ducumentation）是sql中的保留字，将其更改为module并且它应该可以正常工作