如何从 MyBatis 获取 Map<String, Integer>？原因：java.sql.SQLException：getInt() 的无效值 - 'NONE'

Question

我试着关注 Return HashMap in mybatis and use it as ModelAttribute in spring MVC (Option 1) and Mybatis ResultMap is HashMap<String,Object>。我有

@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);

它returns一个错误

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'

查询在 MySQL 和 returns

中工作正常

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

好像没有使用@MapKey注解

我试过了

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

但它给了

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

也试过同样的错误。

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-Spring1.3.2

Answer 1

我必须自己构建 class，但我不喜欢它。愚蠢的是，我必须添加这么多代码才能从数据库中获取简单的 key/value 对。

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>

Answer 2

你应该这样写，

@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);

这是选项 1 的方式。

如何从 MyBatis 获取 Map<String, Integer>？原因：java.sql.SQLException：getInt() 的无效值 - 'NONE'

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

mybatis

spring-mybatis