How do I get a Map<String, Integer> from MyBatis? Cause: java.sql.SQLException: Invalid value for getInt() - 'NONE'

Question

I tried to follow Return HashMap in mybatis and use it as ModelAttribute in spring MVC (Option 1) and Mybatis ResultMap is HashMap<String,Object>. I have

@Select("select sources.host as 'key', count(*) total ... group by host")
@MapKey("key")
Map<String, Integer> getSourcesById(@Param("id")String id, @Param("hitDate")Date hitDate);

It returns an error

Error attempting to get column 'key' from result set. Cause: java.sql.SQLException: Invalid value for getInt() - 'NONE' ; SQL []; Invalid value for getInt() - 'NONE'; nested exception is java.sql.SQLException: Invalid value for getInt() - 'NONE'

The query works fine in MySQL and returns

| key         | total |
+-------------+-------+
| NONE        |    33 |
| twitter.com |     1 |

It's as if it is not using the @MapKey annotation.

I tried

List<AbstractMap.SimpleEntry<String, Integer>> getSourcesById(...)

But it gave

nested exception is org.apache.ibatis.executor.ExecutorException: No constructor found in java.util.AbstractMap$SimpleEntry matching [java.lang.String, java.lang.Long]

Also tried this with the same error.

List<AbstractMap.SimpleEntry<String, Long>>

https://docs.oracle.com/javase/7/docs/api/java/util/AbstractMap.SimpleEntry.html#constructor_summary

MyBatis 3.4.6, MyBatis-Spring 1.3.2

Community · Accepted Answer · 2020-06-20 09:12:55Z

0

I had to build my own class, but I don't like it. It's dumb that I have to add so much code for getting a simple key/value pair from the DB.

Pair.java

public class Pair<T1, T2> {
    public T1 key;
    public T2 value;

    public Pair(T1 k, T2 v) {
        key = k;
        value = v;
    }
    
    public Pair(String k, Long v) {
        key = (T1) k;
        value = (T2) v;
    }

    public T1 getKey() {
        return key;
    }

    public T2 getValue() {
        return value;
    }

}

Mapper.java

List<Pair<String, Long>> getSourcesById(@Param("id")String id, @Param("hitDate")Date hitDate);

Page.jsp

<c:forEach items="${sources}" var="s">${s.value},</c:forEach>

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Dec 7, 2018 at 20:11

Chloe

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Comments

Bing Zhao · Accepted Answer · 2018-12-13 14:58:43Z

0

You should write the following,

@Select("select sources.host as 'key', count(*) total ... group by host")
@MapKey("key")
Map<String, Map<String, Object>> getSourcesById(@Param("id")String id, @Param("hitDate")Date hitDate);

It's the option-1's way.

answered Dec 13, 2018 at 14:58

Bing Zhao

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2 Comments

Chloe Over a year ago

That is a Map of Maps. Why would that be useful? And how would you specify the 2 keys? There are only 2 values, but that requires 3. Presumably you would use the same key for the outer Map as the inner Map, but then what's the point? Might as well just use a List of Maps at that point.

Bing Zhao Over a year ago

@Chloe It's the way that option 1 works, for key "NONE" of the outter map, inner map is "key" -> "NONE", "total" -> 33. You can transform Map<String, Map<String, Object>> to Map<String, Integer> by

Map<String, Integer> anotherMap = map.entrySet().stream()                 .collect(Collectors.toMap(Map.Entry::getKey, it -> (int)it.getValue().get("total")));

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