Unsupported Operation Exception mybatis - sql

Question

So in this code what I want is a random SQL query from the outside that will be loaded into a property file. As of now i've got the property file with a query in it to test this. So i would like some data out, with a headline and all the data beneath. Basically just the data to start with though, as this test should do. But I get the error message that i've linked below. I can't for the life of me figure out where my problem is. Help please! :)
I've got the following code;
DataHandler class.
public class DataHandler{
DataService dataService = new DataService();
public String getPropertyValue() throws IOException {
Properties prop = new Properties();
String propFileName = "randomSqlQuery.properties";
InputStream inputStream = getClass().getClassLoader().getResourceAsStream(propFileName);
prop.load(inputStream);
if (inputStream == null) {
throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
}
String result = prop.getProperty("sqlQuery");
return result;
}
public Data getKeysAndValues() throws IOException {
String query = getPropertyValue();
List<List<Object>> randomSqlQuery = dataService.getRandomSqlQuery(query);
List<List<Object>> recordList = new ArrayList<>();
List<String> headline = new ArrayList();
if (randomSqlQuery != null && randomSqlQuery.size() > 0) {
{
List<Object> record = randomSqlQuery.get(0);
getHeadlines(record, headline);
}
for (int i = 1; i < randomSqlQuery.size(); i++) {
List<Object> singleRecord = randomSqlQuery.get(i);
recordList.add(singleRecord);
System.out.println(recordList);
}
}
return new DataImpl(headline, recordList);
}
private void getHeadlines(List<Object> record, List<String> headline) {
for (Object headlineName : record) {
headline.add((String) headlineName);
System.out.println(headlineName);
}
}
}
DataMapper class
public interface DataMapper {
public List<List<Object>> getRandomSqlQuery(#Param("query") String query);
}
DataMapper XML
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="nd.mappers.DataMapper">
<select id="getRandomSqlQuery" resultType="java.util.List">
${query}
</select>
</mapper>
DataImpl class, which has an interface connected to it
public class DataImpl implements Serializable, Data {
private final List<String> headers;
private final List<List<Object>> records;
public DataImpl(List<String> headers, List<List<Object>> records) {
this.headers = Collections.unmodifiableList(headers);
this.records = Collections.unmodifiableList(records);
}
#Override
public List<String> getHeaders() {
return this.headers;
}
#Override
public List<List<Object>> getRecords() {
return this.records;
}
}
And a DataService class
public class DataService implements DataMapper {
#Override
public List<List<Object>> getRandomSqlQuery(String query) {
SqlSession sqlSession = MyBatisUtil.getSqlSessionFactory().openSession();
try {
DataMapper dataMapper = sqlSession.getMapper(DataMapper.class);
return dataMapper.getRandomSqlQuery(query);
} finally {
sqlSession.close();
}
}
}
Finally the test
//dataHandler instantiated in top
#Test
public void getKeysAndValues() throws IOException {
dataHandler.getKeysAndValues();
}
And here is my error!
### Error querying database. Cause: java.lang.UnsupportedOperationException
### The error may exist in nd/mappers/DataMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT * FROM PERSON ### Cause: java.lang.UnsupportedOperationException
org.apache.ibatis.exceptions.PersistenceException
### Error querying database. Cause: java.lang.UnsupportedOperationException
### The error may exist in nd/mappers/DataMapper.xml
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: SELECT * FROM PERSON
### Cause: java.lang.UnsupportedOperationException
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:111)
No idea what to do. The SQL is coming from the property file. Sorry for massive text.

Answer 1

I just resolved the same error message. The problem lies here:
<select id="getRandomSqlQuery" resultType="Person">
${query}
</select>
The result type should not be a collection but a type that the
collection contains. In your case it should be some Person
POJO. This type then must be defined in the (say mybatis-config.xml) configuration
file:
<typeAliases>
<typeAlias alias="Person" type="com.example.bean.Book"/>
</typeAliases>
Also, you would want to check for null here:
try {
DataMapper dataMapper = qlSession.getMapper(DataMapper.class);
return dataMapper.getRandomSqlQuery(query);
} finally {
if (sqlSession != null) {
sqlSession.close();
}
}