java - DAO Hibernate Java Select All rows into a collection

Question

所以，基本上我在同一个过程中停留了大约 1 周，我想我基本上已经失去了它。我一直在做作业，我无法更改已经构建的内容，但我需要使用那里的内容来获得结果。

我想要做的是从一个表中选择所有行，而不是只使用一个键获取一个行。我正在为此使用 hibernate 和 DAO。我现在只选择了 1 个查询并正在运行，但我面临着获取所有记录并将它们保存为列表或集合的问题。

public CachedObject get(String key) {
    CachedObject rtnValue = null;

    log.debug("Entering get(key) for key = " + key + "...");

    // try to find entry from db as long as key
    // is not in the do not cache list
    if (!getDoNotCacheKeys().contains(key)) {
        try {
            rtnValue = getDao().find( getFetchQueryName(), KEY_PARM_NAME, key);
            // if we got an object back - and it has not expired - reset
            // its last active timestamp value to now and save
            if (rtnValue != null && !rtnValue.hasExpired(getMaxIdle(), getMaxAge())) {
                log.debug("Cache entry being updated with current timestamp...");
                rtnValue.setLastActive(new Timestamp(System.currentTimeMillis()));
                getDao().saveOrUpdate(rtnValue);
            }
        }
        catch (DatabaseException exc) {
            log.error("Exception triggered on get of cache entry with key = " + key, exc);
            if (exc.isSerializationException()) {
                try {
                    log.warn("Serialization of old value triggered exception - proceeding to remove obsolete record for key = " + key + "...");
                    int numRows = getDao().delete(getDeleteQueryName(), KEY_PARM_NAME, key);
                    log.info("The delete for key = " + key + " successfully deleted " + numRows + " rows in the db...");
                }
                catch (DatabaseException exc2) {
                    log.error("Unable to remove record for key " + key + " from the cache db...", exc2);
                }
            }
        }            
    }
    else {
        log.info("Key " + key + " found in do not cache list - no lookup performed...");
    }
    log.debug("Exiting get(key) for key = " + key + "...");

    return rtnValue;
}

然后用于将其添加到缓存

public CachedObject add(String key, CachedObject obj) {
    CachedObject rtnValue = obj;

    log.debug("Entering add(key, obj) for key = " + key + "...");

    // add to the cache as long as the key value is 
    // not in the do not cache list
    if (!getDoNotCacheKeys().contains(key)) {
        // update timestamp values
        long now = System.currentTimeMillis();
        obj.setLastActive(new Timestamp(now));
        obj.setFirstActive(new Timestamp(now));

        // persist obj to cache
        try {
            log.debug("Saving cache object to the db...");
            getDao().saveOrUpdate(obj);
        }
        // if object with same key is already in db - then it must
        // have been added after check or has expired - so just perform get to
        // read it in 
        catch (ConstraintViolationException exc) {
            log.warn("Existing cache object with key = " + key + " found in the database. Attempting to update existing copy via get()...");
            CachedObject dbCopy = get(key);
            if (dbCopy == null) {
                log.error("Unexpected null returned on get of existing cache entry with key = " + key + " !!!");                    
            }
            // now replace serialized data just in case the class
            // has changed and won't deserialize properly
            // also copy over last and first active timestamps
            // since 
            dbCopy.setCacheObject(obj.getCacheObject());
            dbCopy.setLastActive(obj.getLastActive());
            dbCopy.setFirstActive(obj.getFirstActive());
            try {
                getDao().saveOrUpdate(dbCopy);
            }
            catch (DatabaseException exc2) {
                log.error("Unexpected error triggered while updating existing cached object with new serialized content...", exc2);
            }
            // set return to return the db based copy and not the original
            // passed into this method
            rtnValue = dbCopy;

        }
        catch (DatabaseException exc) {
            log.error("Exception triggered on save of cache entry with key = " + key + ": " + obj, exc );
        }            
    }
    else {
        log.info("Key " + key + " found in do not cache list - no add performed...");
    }

    log.debug("Exiting add(key, obj) for key = " + key + "...");

    return rtnValue;
}

我现在想做的是，现在尝试选择所有记录并将它们保存在一个集合中，这样我以后可以通过验证使用它们(仍然需要这样做)，但事实上我不非常了解如何使用 DAO 选择所有记录。

find() 方法非常简单

CachedObject find(String queryName, String keyParmName, Object key) throws DatabaseException;

我在想类似的东西

ArrayList<CachedObject> listObj = getDao().find(fetchAllQueryName, null, getDao());

但是，更改 find() 以返回类似集合的内容。我不知道，我现在很绝望。

任何帮助将不胜感激，谢谢，圣诞快乐。

Answer 1

dandalf 是对的，你必须创建一个类似于

的方法

getDao().getAll()

或

getDao().findAll() 正如您在评论中提到的，此方法不是从 AbstractDao 继承的，那么显然您将 AbstractDao 中的签名作为抽象方法保留，随着功能的增加，引入了不同的方法，您不能仅通过预定义来完成所有事情方法。