I am using MyBatis 3.2.8 in a Play Framework 2.3.6 Java project. I've been struggling for several days with iterating over a list of integers that is passed to a MyBatis mapper within a complex object parameter. Here is my setup:

I have a class called EventFilter in EventFilter.java:

```
public class EventFilter {
private String beginDate;
private String endDate;
private List<Integer> closestCountry;
private List<Integer> territorialWaterStatus;
private List<Integer> vesselCountry;
private String closestCountryInClause;
private String territorialWaterStatusInClause;
private String vesselCountryInClause;

public EventFilter() { }

public EventFilter(JsonNode jsonNode){
    this.beginDate = jsonNode.get("beginDate").asText();
    this.endDate = jsonNode.get("endDate").asText();
    this.closestCountry = JsonHelper.arrayNodeToIntegerList((ArrayNode) jsonNode.get("closestCountry"));
    this.territorialWaterStatus = JsonHelper.arrayNodeToIntegerList((ArrayNode) jsonNode.get("territorialWaterStatus"));
    this.vesselCountry = JsonHelper.arrayNodeToIntegerList((ArrayNode) jsonNode.get("vesselCountry"));
}

public String getBeginDate() {
    return beginDate;
}

public void setBeginDate(String beginDate) {
    this.beginDate = beginDate;
}

public String getEndDate() {
    return endDate;
}

public void setEndDate(String endDate) {
    this.endDate = endDate;
}

public List<Integer> getTerritorialWaterStatus() {
    if(this.territorialWaterStatus.size() > 0) {
        return territorialWaterStatus;
    } else {
        return null;
    }
}

public void setTerritorialWaterStatus(List<Integer> territorialWaterStatus) {
    this.territorialWaterStatus = territorialWaterStatus;
}

public List<Integer> getClosestCountry() {
    if(this.closestCountry.size() > 0) {
        return closestCountry;
    } else {
        return null;
    }
}

public void setClosestCountry(List<Integer> closestCountry) {
    this.closestCountry = closestCountry;
}

public List<Integer> getVesselCountry() {
    if(this.vesselCountry.size() > 0) {
        return vesselCountry;
    } else {
        return null;
    }
}

public void setVesselCountry(List<Integer> vesselCountry) {
    this.vesselCountry = vesselCountry;
}

```

}

This is referenced as a type alias in my mybatis config file:

```
<configuration>

<typeAliases>
    <typeAlias type="models.Event" alias="Event"/>
    <typeAlias type="models.EventFilter" alias="EventFilter"/>
    <typeAlias type="models.Country" alias="Country"/>
</typeAliases>

<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="org.postgresql.Driver"/>
            <property name="url" value="jdbc:postgresql://localhost:5432/mpmap"/>
            <property name="username" value="postgres"/>
            <property name="password" value="dbpw"/>
        </dataSource>
    </environment>
</environments>

<mappers>
    <mapper resource="EventMapper.xml"/>
</mappers>
</configuration>

```

I have a mapper that takes an EventFilter object as its parameter. It should then check if the beginDate, endDate, closestCountry, vesselCountry, and territorialWaterStatus are set. If they are it uses them for the WHERE clause:

```
<select id="getEventsWithFilter" resultType="Event" resultMap="EventResult">
    SELECT ev.id, to_char(ev.occurred_on, 'YYYY-MM-DD') AS occurred_on_date,
        to_char(ev.occurred_on, 'HH24:MI:SS') AS occurred_on_time,
        ST_X(ev.location) AS longitude, ST_Y(ev.location) AS latitude,
        COALESCE(co01.name, 'Unspecified') AS closest_country,
        COALESCE(co02.name, 'Unspecified') AS territorial_water_status,
        COALESCE(co03.name, 'Unspecified') AS vessel_flag_country
    FROM event AS ev
    LEFT JOIN country AS co01
        ON co01.cow_id = ev.location_closest_country_id
    LEFT JOIN country AS co02
        ON co02.cow_id = ev.location_water_status_country_id
    LEFT JOIN country AS co03
        ON co03.cow_id = ev.vessel_flag_country_id
    <where>
        <if test="#{eventFilter.beginDate} != null and #{eventFilter.endDate} != null">
            ev.occurred_on &gt;= #{eventFilter.beginDate}::timestamp AND ev.occurred_on &lt;= #{eventFilter.endDate}::timestamp
        </if>
        <if test="#{eventFilter.closestCountry} != null">
            AND ev.location_closest_country_id IN
            <foreach item="id" index="index" collection="#{eventFilter.closestCountry}" open="(" separator="," close=")">
                #{id}
            </foreach>
        </if>
        <if test="#{eventFilter.territorialWaterStatus} != null">
            AND ev.location_water_status_country_id IN
            <foreach item="id" index="index" collection="#{eventFilter.territorialWaterStatus}" open="(" separator="," close=")">
                #{id}
            </foreach>
        </if>
        <if test="#{eventFilter.vesselCountry} != null">
            AND ev.vessel_flag_country_id IN
            <foreach item="id" index="index" collection="#{eventFilter.vesselCountry}" open="(" separator="," close=")">
                #{id}
            </foreach>
        </if>
    </where>
    ORDER BY ev.occurred_on ASC;
</select>

```

I have the mapper linked into an interface as follows:

```
    public List<Event> getEventsWithFilter(@Param("eventFilter") EventFilter eventFilter);

```

And I am calling it with a MybatisMapper helper class that generates my session as follows:

```
public static List<Event> getEvents(EventFilter eventFilter) {
    MybatisMapper mapper = new MybatisMapper();
    SqlSession session = mapper.getSession();
    EventMapper eventMapper = session.getMapper(EventMapper.class);

    List<Event> events;

    List<Integer> li = eventFilter.getClosestCountry();

    try {
        events = eventMapper.getEventsWithFilter(eventFilter);
    } finally {
        session.close();
    }

    return events;
}

```

**The Problem(s):**

The beginDate and endDate work completely fine by themselves. But I'm having the following problems with the integer lists:

1. The if statement checking if the list is null seems to be getting
ignored, or evaluating to true when it should be false.
2. The integer lists are appearing to be passed as null into the IN clauses.
3. If I comment out the integer list IN clauses, and just to beginDate and
endDate, it works completely fine. However, if I leave the integer
list IN clauses, the query doesn't fail, but it returns an empty
set, as if to say "WHERE column IN ()".

Here is the console logging printed by Play and Mybatis when the mapper/query are executed, along with the EventFilter printing its contents. They're a little lengthy so I put them in pastebin:

* When I pass three countries for each of the three integer lists: <http://pastebin.com/aWcXyikh>
* When I pass only the beginDate and endDate: <http://pastebin.com/CeCv256g>

This became a little longer than I wanted it to, but thanks in advance for any help or suggestions.
['https://Stackoverflow.com/questions/27641563', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1695454/']
try this 

```
<if test="eventFilter.closestCountry != null">
        AND ev.location_closest_country_id IN
        <foreach item="id" index="index" collection="eventFilter.closestCountry" open="(" separator="," close=")">
            ${id}
        </foreach>
    </if>

```
I'm using MyBatis v. 3.4.6.

My case:

```
@Mapper
public interface CorsoMapper {
    List<CorsoEntity> elenco(Filtro filtro);
}

public class Filtro implements Serializable {
    private static final long serialVersionUID = -8357822764110641974L;

    private String codice;
    private List<String> codici;

    public String getCodice() {
        return codice;
    }

    public void setCodice(String codice) {
        this.codice = codice;
    }

    public List<String> getCodici() {
        return codici;
    }

    public void setCodici(List<String> codici) {
        this.codici = codici;
    }
}

```

SQL:

```
<select id="elencoCorsi" parameterType="it.blabla.Filtro" resultMap="corsoMap">
    AND CODICI IN
    <foreach item="c" collection="codici" open="(" separator="," close=")">
       #{c}
    </foreach>
</select>

```

It works without using "index" attribute.