5

我们需要将查询编号附加到我们的应用程序执行的每个查询中。

例如：SELECT * FROM ... WHERE ... QUERYNO 123456；

OpenJPA 支持查询提示，但仅针对特定实现的特定提示。

...
Query q = em.createQuery("select m from Magazine m where ... ");
q.setHint("openjpa.hint.OptimizeResultCount", new Integer(2));
q.setHint("openjpa.FetchPlan.ReadLockMode","WRITE");
List r = q.getResultList();
...

但是根据 JPA 规范和 openjpa “无效提示或特定数据库无法处理的提示将被忽略。否则，无效提示将导致 ArgumentException 被抛出。” 所以指定“QUERYNO”作为提示似乎没有影响。

如何创建自定义查询提示以在运行时指定？

... Query q = em.createQuery("select m from Magazine m where ..."); q.setHint(" com.me.CustomQueryNoHint ", new Integer(2234)); 列表 r = q.getResultList(); ...

4

3 回答 3

0

您是否考虑过编写一个映射到实体返回类型的本机查询，而不是使用 JPQL 并尝试将特定于供应商的内容强加到查询中？

em.createNativeQuery(YOUR_DB2_NATIVE_SQL_QUERY_STRING, Magazine.class)

因为您的本机查询需要选择与实体类中的映射列匹配的列值，所以这对您来说会更有用，但它应该可以工作。当您使用本机 SQL 时，查询引擎不得解析和解释特定于供应商的 SQL，因此最后您的特定于 DB2 的子句应该在运行时传递到底层数据库。

于 2010-11-21T23:59:29.143 回答
0

指定“QUERYNO”作为提示似乎没有影响。

正确的。根据您引用的文档，“QUERYNO”是无效提示，因此被忽略。该文档有些令人困惑，但我相信 if 可以解释为支持您观察到的行为。:-)

如何创建自定义查询提示以在运行时指定？

这是一项艰巨的任务。我不相信 OpenJPA 旨在允许编写自定义查询提示。

我想了更多关于您希望将特定字符串附加到每个 SQL 的实际问题，我认为在 OpenJPA 中这样做并不容易。也许您可以为您的 JDBC 驱动程序编写一个包装器，并将您的字符串附加到每个 SQL 中？

于 2010-11-16T14:48:15.387 回答
0

不完整的答案，但只是一个指针......

查询计数器

public class QueryCounter {
    private static long COUNTER = 0;

    private static long next() {
        return ++COUNTER;
    }

    private static String getHintValue() {
        return "/*Query No. " + next() + " */";
    }

    public static void setQueryCount(Query query) {
        /* EclipseLink */
        //query.setHint(QueryHints.HINT, getHintValue());
            query.setHint("eclipselink.sql.hint", getHintValue());

        /* OpenJPA + Oracle */
        //query.setHint("openjpa.hint.OracleSelectHint", getQueryHint());

        /* OpenJPA + MySQL */
        //query.setHint("openjpa.hint.MySQLSelectHin", getQueryHint());
    }
}

用法

Organization sun = new Organization("Sun");
        em.persist(sun);
        tx.commit();
        Assert.assertNotNull(sun.getEntityId());

        Query query = em.createQuery("SELECT org.entityId FROM Organization org WHERE org.entityId = " + sun.getEntityId());
        QueryCounter.setQueryCount(query);
        query.getResultList();

        /*ServerSession does NOT log ReadObjectQuery??*/
        query = em.createQuery("SELECT org FROM Organization org WHERE org.entityId = " + sun.getEntityId());
        QueryCounter.setQueryCount(query);
        query.getResultList();

        query = em.createQuery("SELECT org.entityId FROM Organization org WHERE org.entityId = " + sun.getEntityId());
        QueryCounter.setQueryCount(query);
        query.getResultList();

安慰

[EL Finest]: 2010-11-20 19:06:16.45--UnitOfWork(717879615)--Thread(Thread[main,5,main])--Execute query ReportQuery(referenceClass=Organization sql="SELECT entity_id FROM organization_tt WHERE (entity_id = ?)")
[EL Fine]: 2010-11-20 19:06:16.475--ServerSession(699542937)--Connection(1949550475)--Thread(Thread[main,5,main])--SELECT /*Query No. 1 */ entity_id FROM organization_tt WHERE (entity_id = ?)
    bind => [1]
[EL Finest]: 2010-11-20 19:06:23.372--UnitOfWork(717879615)--Thread(Thread[main,5,main])--Execute query ReadObjectQuery(referenceClass=Organization sql="SELECT entity_id, name FROM organization_tt WHERE (entity_id = ?)")
[EL Finest]: 2010-11-20 19:06:35.916--UnitOfWork(717879615)--Thread(Thread[main,5,main])--Execute query ReportQuery(referenceClass=Organization sql="SELECT entity_id FROM organization_tt WHERE (entity_id = ?)")
[EL Fine]: 2010-11-20 19:06:35.92--ServerSession(699542937)--Connection(1949550475)--Thread(Thread[main,5,main])--SELECT /*Query No. 3 */ entity_id FROM organization_tt WHERE (entity_id = ?)
    bind => [1]

OpenJPA 有类似的概念1.8.7。特定于数据库的提示。看看这些具体的提示是否能解决你的目的。

更新的答案

@Eddie，看看这是否可以帮助你............

自定义日志工厂

    public class MyLogFactory extends org.apache.openjpa.lib.log.LogFactoryImpl {

    /* copied from LogFactoryImpl.NEWLINE */
    private static final String NEWLINE = J2DoPrivHelper.getLineSeparator();

    private boolean sqlLogger;

    @Override
    public Log getLog(String channel) {
        if("openjpa.jdbc.SQL".equals(channel)) { // OR equalsIgnoreCase(channel) ??? 
            sqlLogger = true;
        }
        return super.getLog(channel);
    }

    @Override
    protected LogImpl newLogImpl() {
        if(sqlLogger) {
            sqlLogger = false; /* once an SQL Logger is created, we dont't need any more instances */
            return new LogImpl() {
                private long sqlCounter = 0;

                @Override
                protected String formatMessage(short level, String message, Throwable t) {
                    if(isSQLString(message)) {
                        StringBuffer formattedMessage = new StringBuffer(super.formatMessage(level, message, t));
                        StringBuffer queryNo = new StringBuffer();
                        queryNo.append("  [Query # ").append(++sqlCounter).append("]").append(NEWLINE);
                        formattedMessage.delete(formattedMessage.length() - NEWLINE.length(), formattedMessage.length());
                        formattedMessage.append(queryNo);
                        return formattedMessage.toString();
                    }
                    return super.formatMessage(level, message, t);
                }

                /* just a sample implementation; checks whether message contains the word "executing"
                 * more concrete implementation should check the message for SELECT, UPDATE, INSERT INTO, ALTER.... clauses */
                private boolean isSQLString(String message) {
                    if(message.contains("executing")) {
                        return true;
                    }
                    return false;
                }

            };
        }
        return super.newLogImpl();
    }

}

持久性.xml

<property name="openjpa.Log" value="org.opensource.logger.MyLogFactory(DefaultLevel=WARN, Runtime=INFO, Tool=INFO, SQL=TRACE)"/>

测试

EntityManager em = Persistence.createEntityManagerFactory("default").createEntityManager();
EntityTransaction tx = em.getTransaction();
tx.begin();
Person person = new Person();
person.setName("Bond-OO7");
person.setAge(22);
em.persist(person);
tx.commit();
em.close();

安慰

............
2084  default  TRACE  [main] openjpa.jdbc.SQL - <t 346613126, conn 1551158018> executing prepstmnt 556472773 SELECT SEQUENCE_OWNER AS SEQUENCE_SCHEMA, SEQUENCE_NAME FROM ALL_SEQUENCES  [Query # 1]
2136  default  TRACE  [main] openjpa.jdbc.SQL - <t 346613126, conn 1551158018> [52 ms] spent
2305  default  TRACE  [main] openjpa.jdbc.SQL - <t 346613126, conn 2026561073> executing prepstmnt 6637010 INSERT INTO Person (id, age, name) VALUES (?, ?, ?) [params=?, ?, ?]  [Query # 2]
2306  default  TRACE  [main] openjpa.jdbc.SQL - <t 346613126, conn 2026561073> [1 ms] spent
............

参考

于 2010-11-20T13:45:41.970 回答