Does Apache OFBiz delegator API support fetching list of records from database by limit or offset

问题

Let's say we have to fetch only 5 records from a table but my where clause is matching 25k records in database. So is there a way in ofbiz framework to just select 5 records rather than getting a list from database and then taking just 5 from the list?

If limit is not possible (since ofbiz API is database agnostic) what are my other alternatives?

回答1:

I would you suggest you to take a look into this entity engine cookbook

Essentially for getting limited set of rows from database you would do:

// first get a list iterator
productsELI = delegator.findListIteratorByCondition("Product", 
  new EntityExpr("productId", EntityOperator.NOT_EQUAL, null), 
                  UtilMisc.toList("productId"), null);

// then get a partial list by count TO RETURN first 5 records
productsELI.getPartialList(0, 5);

// and finally just close the iterator
productsELI.close();

Also if you prefer to send direct SQL to your database then just do like this:

// gets the helper (localmysql, localpostgres, etc.) for your entity group org.ofbiz
String helperName = delegator.getGroupHelperName("org.ofbiz");
SQLProcessor sqlproc = new SQLProcessor(helperName);
sqlproc.prepareStatement("SELECT * FROM PARTY LMIT 0, 5");
ResultSet rs1 = sqlproc.executeQuery();

// and then get your data from ResultSet like regular JDBC

来源：https://stackoverflow.com/questions/5410461/does-apache-ofbiz-delegator-api-support-fetching-list-of-records-from-database-b