Spring JPA repoistory findBy IN List - allow null

问题

Short Description

How do I make findBy<Field>In work with IN when the array list input is null. e.g. ignore it. What would your DAO for this look like?

Longer description.

Imagine you have creating a search for users page.

in the application. You have various options to filter on.

created (date range always given)
Country (when null ignore and search all countries)
AgeRange
Job Title
etc...

Now say you want to search for all users in a given date range in a list of countries.

When searching for users I will always search for a date joined however if I have not selected a country I want it to search for all countries.

I am planning on adding several more filter options other than country. So I don't really want to create lots of findBy methods for each possible field combination.

DAO

@Repository
public interface UserDao extends JpaRepository<User, Long> {

    public List<BeatRate> findByCreatedBetweenAndCountryIn(Date from, Date to, ArrayList<String> countryList );

}

Test

@Test
public void test() throws ParseException {

    Date from = new SimpleDateFormat( "yyyy-MM-dd" ).parse( "2015-01-01" );
    Date to   = new SimpleDateFormat("yyyy-MM-dd").parse("2015-05-15");

    //ArrayList<String> countryList = new ArrayList<String>();
    //countryList.add("UK");
    //countryList.add("Australia");
    //countryList.add("Japan");   // works ok when I have a list

    countryList = null;  // I want it to search for all countries when this is null -- this errors and doesnt work..  

    List<BeatRate> beatRates = beatRateDao.findByCreatedBetweenAndRentalCountryIn(from, to, countryList);

    Assert.assertTrue(beatRates.size()>0);

}

回答1:

You can have two methods:

beatRateDao.findByCreatedBetweenAndRentalCountryIn(from, to, countryList);

and

beatRateDao.findByCreatedBetweenAndRental(from, to);

Then simply pick one based on countryList:

List<BeatRate> beatRates = (countryList != null && !countryList.isEmpty())
    ?  beatRateDao.findByCreatedBetweenAndRentalCountryIn(from, to, countryList)
    : beatRateDao.findByCreatedBetweenAndRental(from, to);

The IN clause requires a non-nullable and non empty argument list as otherwise the query will fail.

On PostgreSQL, if you try to run a query like this:

select * 
from product 
where quantity in ( )

you get the following error:

ERROR:  syntax error at or near ")"
LINE 3: where quantity in ( )
                            ^
********** Error **********

ERROR: syntax error at or near ")"
SQL state: 42601
Character: 45

来源：https://stackoverflow.com/questions/28898132/spring-jpa-repoistory-findby-in-list-allow-null

标签

Spring

hibernate

jpa

spring-data

findby