CODEWITHSUNDEEP
javaoracle11gspring-mybatis
killer_nudt
killer_nudt

Reputation: 81

Why cann't I get a value from a Map<String,String> variable that got from mybatis-based sql query?

I got a magic problem when handling oracle db query operaiotn with mybatis. I query some columns out of my oracle database and set the resultType to Map,the query worked fine but when I tried to get a value from the Map variable and transfer the value to a String Object,I got a cast Exception：“java.sql.Timestamp cannot be cast to java.lang.String”

My Java Mapper code are like following:

@Mapper
public interface DynamicDataMapper {
    Map<String, String> selectDataDetail(@Param("traceRuleDO") TraceRuleDO traceRuleDO, @Param("traceQueryVO") TraceQueryVO traceQueryVO);
}

My Mybatis XML mapper files are like following:

    <select id="selectDataDetail" resultType="java.util.Map" statementType="STATEMENT" >
       <!--select ${traceRuleDO.shownColumns}-->
        select *
        from ${traceRuleDO.tableName}
        where ${traceRuleDO.primaryKey} = ${traceQueryVO.keyValue}
        <if test="traceQueryVO.secondaryKeyName != null and traceQueryVO.secondaryKeyName != ''">
            and ${traceRuleDO.secondaryKey} = ${traceQueryVO.secondaryKeyValue}
        </if>
    </select>

When I query a table with this interface,the query worked.but when I tried to get a value that of "Date” types in oracle database and tried to set the value to a String type variable,the exception occured:

String date = dataMap.get("startDate");//the startDate is of "Date” type in db

what Confused me is that why is it ok to query and get a result but not when I got value from the Map？

Besides the cause of this problem, I am also curious about the solution to meet such type of query needs.Thanks for your help!

Upvotes: 0

Views: 518

Answers (2)

jinzuchi
jinzuchi

Reputation: 148

java generic types would be erasured after compiled, so the type of value in map was the actually type, not the type you declared by generic

Upvotes: 0

tom li
tom li

Reputation: 56

i think String date = dataMap.get("startDate"); like String date = (String)Object;,if object is not String, then whill throw a ClassCastException, you can change Map<String, String> to Map<String, Object> or create a mybatis typeHandlers. you can try it, I'm not sure I'm right, but i hope i can help you.

Upvotes: 2

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