How to do a timestamp comparison with JPA query?

问题:

We need to make sure only results within the last 30 days are returned for a JPQL query. An example follows:

Date now = new Date();
Timestamp thirtyDaysAgo = new Timestamp(now.getTime() - 86400000*30);

Query query = em.createQuery(
  "SELECT msg FROM Message msg "+
  "WHERE msg.targetTime < CURRENT_TIMESTAMP AND msg.targetTime > {ts, '"+thirtyDaysAgo+"'}");
List result = query.getResultList();

Here is the error we receive:

<openjpa-1.2.3-SNAPSHOT-r422266:907835 nonfatal user error> org.apache.openjpa.persistence.ArgumentException: An error occurred while parsing the query filter 'SELECT msg FROM BroadcastMessage msg WHERE msg.targetTime < CURRENT_TIMESTAMP AND msg.targetTime > {ts, '2010-04-18 04:15:37.827'}'. Error message: org.apache.openjpa.kernel.jpql.TokenMgrError: Lexical error at line 1, column 217.  Encountered: "{" (123), after : ""

Help!

回答1:

So the query you input is not JPQL (which you could see by referring to the JPA spec). If you want to compare a field with a Date then you input the Date as a parameter to the query

msg.targetTime < CURRENT_TIMESTAMP AND msg.targetTime > :param

THIS IS NOT SQL.

回答2:

The JDBC escape syntax may not be supported in the version of OpenJPA that you're using. The documentation for the latest 1.2.x release is here: http://openjpa.apache.org/builds/1.2.2/apache-openjpa-1.2.2/docs/manual/manual.html#jpa_langref_lit .

The documentation mentioned earlier refers to the docs for OpenJPA 2.0.0 (latest): http://openjpa.apache.org/builds/latest/docs/manual/jpa_langref.html#jpa_langref_lit

That said is there any reason why you want to inject a string into your JPQL? What about something like the following snippet?

Date now = new Date();
Date thirtyDaysAgo = new Date(now.getTime() - (30 * MS_IN_DAY));

Query q = em.createQuery("Select m from Message m " 
    + "where m.targetTime < :now and m.targetTime > :thirtyDays");
q.setParameter("now", now); 
q.setParameter("thirtyDays", thirtyDaysAgo);

List<Message> results = (List<Message>) q.getResultList();