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;/*** 将查询结果映射成map的注解，其中第一个字段为key，第二个字段为value.* <p>* 注：返回类型必须为{@link java.util.Map Map<K, V>}。K/V的类型通过MyBatis的TypeHander进行类型转换，如有必要可自定义TypeHander。** @author yunjie.du* @date 2016/12/22 18:44*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.METHOD })
public @interface MapF2F {/*** 是否允许key重复。如果不允许，而实际结果出现了重复，会抛出org.springframework.dao.DuplicateKeyException。* * @return*/boolean isAllowKeyRepeat() default true;/*** 对于相同的key，是否允许value不同(在允许key重复的前提下)。如果允许，则按查询结果，后面的覆盖前面的；如果不允许，则会抛出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的拦截器* * @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);@Overridepublic Object intercept(Invocation invocation) throws Throwable {MetaObject metaStatementHandler = ReflectUtil.getRealTarget(invocation);MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("mappedStatement");String className = StringUtils.substringBeforeLast(mappedStatement.getId(), ".");// 当前类String currentMethodName = StringUtils.substringAfterLast(mappedStatement.getId(), ".");// 当前方法Method currentMethod = findMethod(className, currentMethodName);// 获取当前Methodif (currentMethod == null || currentMethod.getAnnotation(MapF2F.class) == null) {// 如果当前Method没有注解MapF2Freturn invocation.proceed();}// 如果有MapF2F注解，则这里对结果进行拦截并转换MapF2F mapF2FAnnotation = currentMethod.getAnnotation(MapF2F.class);Statement statement = (Statement) invocation.getArgs()[0];Pair<Class<?>, Class<?>> kvTypePair = getKVTypeOfReturnMap(currentMethod);// 获取返回Map里key-value的类型TypeHandlerRegistry typeHandlerRegistry = mappedStatement.getConfiguration().getTypeHandlerRegistry();// 获取各种TypeHander的注册器return result2Map(statement, typeHandlerRegistry, kvTypePair, mapF2FAnnotation);}@Overridepublic Object plugin(Object obj) {return Plugin.wrap(obj, this);}@Overridepublic void setProperties(Properties properties) {}/*** 找到与指定函数名匹配的Method。** @param className* @param targetMethodName* @return* @throws Throwable*/private Method findMethod(String className, String targetMethodName) throws Throwable {Method[] methods = Class.forName(className).getDeclaredMethods();// 该类所有声明的方法if (methods == null) {return null;}for (Method method : methods) {if (StringUtils.equals(method.getName(), targetMethodName)) {return method;}}return null;}/*** 获取函数返回Map中key-value的类型* * @param mapF2FMethod* @return left为key的类型，right为value的类型*/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,返回类型必须是java.util.Map类型！！！method=" + mapF2FMethod);}return new Pair<>((Class<?>) parameterizedType.getActualTypeArguments()[0],(Class<?>) parameterizedType.getActualTypeArguments()[1]);}return new Pair<>(null, null);}/*** 将查询结果映射成Map，其中第一个字段作为key，第二个字段作为value.* * @param statement* @param typeHandlerRegistry MyBatis里typeHandler的注册器，方便转换成用户指定的结果类型* @param kvTypePair 函数指定返回Map key-value的类型* @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)) {// 该key已存在if (!mapF2FAnnotation.isAllowKeyRepeat()) {// 判断是否允许key重复throw new DuplicateKeyException("MapF2F duplicated key!key=" + key);}Object preValue = map.get(key);if (!mapF2FAnnotation.isAllowValueDifferentWithSameKey() && !Objects.equals(value, preValue)) {// 判断是否允许value不同throw new DuplicateKeyException("MapF2F different value with same key!key=" + key + ",value1="+ preValue + ",value2=" + value);}}map.put(key, value);// 第一列作为key,第二列作为value。
        }res.add(map);return res;}/*** 结果类型转换。* <p>* 这里借用注册在MyBatis的typeHander（包括自定义的），方便进行类型转换。* * @param resultSet* @param columnIndex 字段下标，从1开始* @param typeHandlerRegistry MyBatis里typeHandler的注册器，方便转换成用户指定的结果类型* @param javaType 要转换的Java类型* @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;/*** 反射工具类*/
public class ReflectUtil {private static final Logger logger = LoggerFactory.getLogger(ReflectUtil.class);/*** 分离最后一个代理的目标对象* * @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;}}

View Code

    <!-- 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>

    /*** 批量获取用户姓名* * @param ids* @return key为ID，value为username*/@MapF2F()Map<Long, String> queryUserNamesByIds(@Param("ids") List<Long> ids);

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