CODEWITHSUNDEEP
javamybatis
Paul Johnson
Paul Johnson

Reputation: 37

Select Column of Integers with MyBatis

I'm trying to use MyBatis to get a single column from a table that contains Integers. I'm presuming to extract it as a List (though I may be wrong on this point!)

This is my mapper.xml

<select id="getPersonIds" resultType="java.util.List">
    SELECT PersonId
        FROM TestDB.users
</select>

This is my Mapper Interface

package com.paulmjohnson.Mappers;
import java.util.List;

public interface PersonMapper {

    List<Integer> getPersonIds();

}

My DAO:

public List<Integer> getPersonIds() {
        SqlSession session = MyBatisUtil.getSqlSessionFactory().openSession();
        logger.info("Getting Person IDs");
        List<Integer> personIds = session.selectList("com.paulmjohnson.Mappers.PersonMapper.getPersonIds");
        session.close();
        return personIds;
}

And how I'm calling it:

PeopleDAO peopleDAO = new PeopleDAO();
List<Integer> personIds = peopleDAO.getPersonIds();

MyBatis seems to be creating the SELECT query I'm expecting:

2019-12-26 09:39:06,677 [main] [DEBUG] c.p.Mappers.PersonMapper.getPersonIds - ==>  Preparing: SELECT PersonId FROM TestDB.users 
2019-12-26 09:39:06,678 [main] [DEBUG] c.p.Mappers.PersonMapper.getPersonIds - ==> Parameters:

When I run it I get this:

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.UnsupportedOperationException
### The error may exist in person-mapper.xml
### The error may involve com.paulmjohnson.Mappers.PersonMapper.getPersonIds
### The error occurred while handling results
### SQL: SELECT PersonId             FROM TestDB.users
### Cause: java.lang.UnsupportedOperationException
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:149)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:135)
    at com.paulmjohnson.DAO.PeopleDAO.getPersonIds(PeopleDAO.java:82)
    at com.paulmjohnson.UsingBuckets.main(UsingBuckets.java:105)
Caused by: java.lang.UnsupportedOperationException
    at org.apache.ibatis.reflection.wrapper.CollectionWrapper.findProperty(CollectionWrapper.java:48)
    at org.apache.ibatis.reflection.MetaObject.findProperty(MetaObject.java:85)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.createAutomaticMappings(DefaultResultSetHandler.java:493)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyAutomaticMappings(DefaultResultSetHandler.java:517)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:402)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:354)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:328)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:301)
    at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:194)
    at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:65)
    at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
    at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
    at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
    at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
    at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)
    ... 4 more

I'm fairly sure I'm doing something very silly here!

Upvotes: 0

Views: 2111

Answers (1)

shengshu
shengshu

Reputation: 61

In your mapper.xml you have resultType="java.util.List" You should use resultType="java.lang.Integer" instead.

Upvotes: 2

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