sql查詢返回值使用map封裝多個key和value實例

public class MapResultHandler implements ResultHandler {
    private final Map mappedResults = new HashMap();
    @Override
    public void handleResult(ResultContext context) {
        @SuppressWarnings("rawtypes")
        Map map = (Map) context.getResultObject();
        mappedResults.put(map.get("key"), map.get("value"));
    }
    public Map getMappedResults() {
        return mappedResults;
    }
}

  <resultMap id="retMap" type="java.util.HashMap">
        <result column="keyName" property="key" javaType="java.lang.String"/>
        <result column="val" property="value" javaType="java.math.BigDecimal"/>
    </resultMap> 

SELECT F_NAME keyName,nvl(sum (F_METADATA_VALUE),0) val from 表名
GROUP BY F_CODE, F_NAME

 @Autowired
    private SqlSessionFactory sqlSessionFactory;
    private static final String mapperPath = "mapper的路徑.";      
  Map<String, Object> parameter = new HashMap<>();
  //設置參數
        parameter.put("query", query);
  //mapper的方法名
        String methodName = "selectMedicineSurvey";
        //查詢數據使用Map封裝
        Map<String, BigDecimal> medicineSurveyMap = getStringBigDecimalMap(mapperPath, parameter, methodName);
    //查詢數據使用Map封裝
    private Map<String, BigDecimal> getStringBigDecimalMap(String mapperPath, Map<String, Object> parameter, String methodName) {
        SqlSession sqlSession = sqlSessionFactory.openSession(true);
        MapResultHandler handler = new MapResultHandler();
        sqlSession.select(mapperPath + methodName, parameter, handler);
       //關流
        sqlSession.close();
         //獲取結果
        return (Map<String, BigDecimal>) handler.getMappedResults();
    }

sqlSession.close();

package com.adu.spring_test.mybatis.annotations;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * 將查詢結果映射成map的註解，其中第一個字段為key，第二個字段為value.
 * <p>
 * 註：返回類型必須為{@link java.util.Map Map<K, V>}。K/V的類型通過MyBatis的TypeHander進行類型轉換，如有必要可自定義TypeHander。
 *
 * @author yunjie.du
 * @date 2016/12/22 18:44
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD })
public @interface MapF2F {
    /**
     * 是否允許key重復。如果不允許，而實際結果出現瞭重復，會拋出org.springframework.dao.DuplicateKeyException。
     * 
     * @return
     */
    boolean isAllowKeyRepeat() default true;
    /**
     * 對於相同的key，是否允許value不同(在允許key重復的前提下)。如果允許，則按查詢結果，後面的覆蓋前面的；如果不允許，則會拋出org.springframework.dao.DuplicateKeyException。
     * 
     * @return
     */
    boolean isAllowValueDifferentWithSameKey() default false;
}

package com.adu.spring_test.mybatis.interceptor;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Properties;
import org.apache.commons.lang3.StringUtils;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.type.TypeHandler;
import org.apache.ibatis.type.TypeHandlerRegistry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DuplicateKeyException;
import com.adu.spring_test.mybatis.annotations.MapF2F;
import com.adu.spring_test.mybatis.util.ReflectUtil;
import javafx.util.Pair;
/**
 * MapF2F的攔截器
 * 
 * @author yunjie.du
 * @date 2016/12/22 18:44
 */
@Intercepts(@Signature(method = "handleResultSets", type = ResultSetHandler.class, args = { Statement.class }))
public class MapF2FInterceptor implements Interceptor {
    private Logger logger = LoggerFactory.getLogger(MapF2FInterceptor.class);
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        MetaObject metaStatementHandler = ReflectUtil.getRealTarget(invocation);
        MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("mappedStatement");
        String className = StringUtils.substringBeforeLast(mappedStatement.getId(), ".");// 當前類
        String currentMethodName = StringUtils.substringAfterLast(mappedStatement.getId(), ".");// 當前方法
        Method currentMethod = findMethod(className, currentMethodName);// 獲取當前Method
        if (currentMethod == null || currentMethod.getAnnotation(MapF2F.class) == null) {// 如果當前Method沒有註解MapF2F
            return invocation.proceed();
        }
        // 如果有MapF2F註解，則這裡對結果進行攔截並轉換
        MapF2F mapF2FAnnotation = currentMethod.getAnnotation(MapF2F.class);
        Statement statement = (Statement) invocation.getArgs()[0];
        Pair<Class<?>, Class<?>> kvTypePair = getKVTypeOfReturnMap(currentMethod);// 獲取返回Map裡key-value的類型
        TypeHandlerRegistry typeHandlerRegistry = mappedStatement.getConfiguration().getTypeHandlerRegistry();// 獲取各種TypeHander的註冊器
        return result2Map(statement, typeHandlerRegistry, kvTypePair, mapF2FAnnotation);
    }
    @Override
    public Object plugin(Object obj) {
        return Plugin.wrap(obj, this);
    }
    @Override
    public void setProperties(Properties properties) {
    }
    /**
     * 找到與指定函數名匹配的Method。
     *
     * @param className
     * @param targetMethodName
     * @return
     * @throws Throwable
     */
    private Method findMethod(String className, String targetMethodName) throws Throwable {
        Method[] methods = Class.forName(className).getDeclaredMethods();// 該類所有聲明的方法
        if (methods == null) {
            return null;
        }
        for (Method method : methods) {
            if (StringUtils.equals(method.getName(), targetMethodName)) {
                return method;
            }
        }
        return null;
    }
    /**
     * 獲取函數返回Map中key-value的類型
     * 
     * @param mapF2FMethod
     * @return left為key的類型，right為value的類型
     */
    private Pair<Class<?>, Class<?>> getKVTypeOfReturnMap(Method mapF2FMethod) {
        Type returnType = mapF2FMethod.getGenericReturnType();
        if (returnType instanceof ParameterizedType) {
            ParameterizedType parameterizedType = (ParameterizedType) returnType;
            if (!Map.class.equals(parameterizedType.getRawType())) {
                throw new RuntimeException(
                        "[ERROR-MapF2F-return-map-type]使用MapF2F,返回類型必須是java.util.Map類型！！！method=" + mapF2FMethod);
            }
            return new Pair<>((Class<?>) parameterizedType.getActualTypeArguments()[0],
                    (Class<?>) parameterizedType.getActualTypeArguments()[1]);
        }
        return new Pair<>(null, null);
    }
    /**
     * 將查詢結果映射成Map，其中第一個字段作為key，第二個字段作為value.
     * 
     * @param statement
     * @param typeHandlerRegistry MyBatis裡typeHandler的註冊器，方便轉換成用戶指定的結果類型
     * @param kvTypePair 函數指定返回Map key-value的類型
     * @param mapF2FAnnotation
     * @return
     * @throws Throwable
     */
    private Object result2Map(Statement statement, TypeHandlerRegistry typeHandlerRegistry,
            Pair<Class<?>, Class<?>> kvTypePair, MapF2F mapF2FAnnotation) throws Throwable {
        ResultSet resultSet = statement.getResultSet();
        List<Object> res = new ArrayList();
        Map<Object, Object> map = new HashMap();
        while (resultSet.next()) {
            Object key = this.getObject(resultSet, 1, typeHandlerRegistry, kvTypePair.getKey());
            Object value = this.getObject(resultSet, 2, typeHandlerRegistry, kvTypePair.getValue());
            if (map.containsKey(key)) {// 該key已存在
                if (!mapF2FAnnotation.isAllowKeyRepeat()) {// 判斷是否允許key重復
                    throw new DuplicateKeyException("MapF2F duplicated key!key=" + key);
                }
                Object preValue = map.get(key);
                if (!mapF2FAnnotation.isAllowValueDifferentWithSameKey() && !Objects.equals(value, preValue)) {// 判斷是否允許value不同
                    throw new DuplicateKeyException("MapF2F different value with same key!key=" + key + ",value1="
                            + preValue + ",value2=" + value);
                }
            }
            map.put(key, value);// 第一列作為key,第二列作為value。
        }
        res.add(map);
        return res;
    }
    /**
     * 結果類型轉換。
     * <p>
     * 這裡借用註冊在MyBatis的typeHander（包括自定義的），方便進行類型轉換。
     * 
     * @param resultSet
     * @param columnIndex 字段下標，從1開始
     * @param typeHandlerRegistry MyBatis裡typeHandler的註冊器，方便轉換成用戶指定的結果類型
     * @param javaType 要轉換的Java類型
     * @return
     * @throws SQLException
     */
    private Object getObject(ResultSet resultSet, int columnIndex, TypeHandlerRegistry typeHandlerRegistry,
            Class<?> javaType) throws SQLException {
        final TypeHandler<?> typeHandler = typeHandlerRegistry.hasTypeHandler(javaType)
                ? typeHandlerRegistry.getTypeHandler(javaType) : typeHandlerRegistry.getUnknownTypeHandler();
        return typeHandler.getResult(resultSet, columnIndex);
    }
}

package com.adu.spring_test.mybatis.util;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
 * 反射工具類
 */
public class ReflectUtil {
    private static final Logger logger = LoggerFactory.getLogger(ReflectUtil.class);
    /**
     * 分離最後一個代理的目標對象
     * 
     * @param invocation
     * @return
     */
    public static MetaObject getRealTarget(Invocation invocation) {
        MetaObject metaStatementHandler = SystemMetaObject.forObject(invocation.getTarget());
        while (metaStatementHandler.hasGetter("h")) {
            Object object = metaStatementHandler.getValue("h");
            metaStatementHandler = SystemMetaObject.forObject(object);
        }
        while (metaStatementHandler.hasGetter("target")) {
            Object object = metaStatementHandler.getValue("target");
            metaStatementHandler = SystemMetaObject.forObject(object);
        }
        return metaStatementHandler;
    }
}

<!-- session factory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="configLocation" value="classpath:mybatis/mybatis-data-config.xml" />
        <property name="mapperLocations" value="classpath:mapper/**/*.xml" />
        <property name="plugins">
            <array>
                <bean class="com.adu.spring_test.mybatis.interceptor.MapF2FInterceptor"/>
            </array>
        </property>
    </bean>

/**
 * 批量獲取用戶姓名
 *
 * @param ids
 * @return key為ID，value為username
 */
@MapF2F()
Map<Long, String> queryUserNamesByIds(@Param("ids") List<Long> ids);

<select id="queryUserNamesByIds" resultType="map">
    SELECT id, user_name
    FROM user_info
    WHERE id IN
        <foreach collection="ids" open="(" close=")" separator="," item="item">
            #{item}
        </foreach>
</select>