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https://issues.apache.org/jira/browse/IBATIS-466?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Clinton Begin closed IBATIS-466.
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Resolution: Won't Fix
As the comments imply, this is not something we can fix... all of the rows are
required for an accurate group by. At best we may be able to throw an
exception upon attempting to use both together. We'll probably wait until v3
to add such an exception though. While I can't think of one, there is a slight
possibility of someone actually making effective use of this combination of
features...(?)
> Incorrect behaviour when combining RowHandler with groupBy
> ----------------------------------------------------------
>
> Key: IBATIS-466
> URL: https://issues.apache.org/jira/browse/IBATIS-466
> Project: iBatis for Java
> Issue Type: Bug
> Components: SQL Maps
> Affects Versions: 2.3.0
> Reporter: William Shields
>
> Assuming:
> CREATE TABLE Person {
> person_id NUMBER PRIMARY KEY,
> name VARCHAR2(100)
> )
> CREATE TABLE Album (
> album_id NUMBER PRIMARY KEY,
> owner NUMBER REFERENCES (Person.person_id),
> name VARCHAR2(100)
> )
> and
> public class Person {
> private long personId;
> private String name;
> private List<Album> albums;
> ...
> }
> public class Album {
> private long albumId;
> private long owner;
> private String name;
> ...
> }
> with query:
> <resultMap id="album" class="Abum">
> <result property="albumId" column="ALBUM_ID"/>
> <result property="owner" column="PERSON_ID"/>
> <result property="name" column="ALBUM_NAME"/>
> </resultMap>
> <resultMap id="person" class="Person" groupBy="personId">
> <result property="personId" column="PERSON_ID"/>
> <result property="name" column="PERSON_NAME"/>
> <result property="albums" resultMap="album"/>
> </resultMap>
> <select id="selectAlbums" resultMap="person">
> SELECT person_id, p.name person_name, album_id, a.name album_name
> FROM Person p, Album a
> WHERE person_id = owner
> </select>
> with data:
> Person:
> 1 John
> 2 Mary
> Album:
> 10 1 "Bat Out Of Hell"
> 11 2 "The Wall"
> 12 2 "Eyes Open"
> 12 2 "White Ladder"
> Now, queryForList() works correctly. Two Person objects are returned. The
> first (John) has 1 album, Mary has 3. If instead you do:
> queryWithRowHandler("....selectAlbums", new RowHandler() {
> public void handleRow(Object valueObject) {
> Person p = (Person)valueObject;
> System.out.println(p.getName() + " has " + p.getAlbums().size() + "
> albums");
> }
> }
> It displays 1 for each of the two rows. The RowHandler is being called on
> the first row and then it continues to add to the sub-list. This is a real
> problem if you want to process the fully loaded value object. I've come up
> with this workaround:
> public interface TypedRowHandler<T> {
> void handle(T t);
> }
> public class CleverRowHandler<T> implements RowHandler {
> TypedRowHandler<T> handler;
> private T last;
> public CleverRowHandler(TypedRowHandler<T> handler) {
> this.handler = handler;
> }
> public void handleRow(Object valueObject) {
> flush();
> last = (T)valueObject;
> }
> public void flush() {
> if (last != null) {
> handler.handler(last);
> }
> last = null;
> }
> }
> with DAO code:
> public void processPersons() {
> CleverRowHandler<Person> rh = new CleverRowHandler<T>(new
> TypedRowHandler<Person>() {
> public void handle(Person p) {
> // do whatever
> }
> };
> try {
> getSqlMapClientTemplate().queryWithRowHandler("....selectPersons", rh);
> } finally {
> rh.flush();
> }
> }
> but that's rather messy. I believe that the current behaviour is a bug and
> introduces potential threading issues (in my case my row handler creates a
> Runnable and submits it to a ExecutorService, which is a problem if ibatis is
> still adding objects to the sub-list).
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