在Apache Flink中，当你修改MapState中的对象时，它不会自动更新。你需要显式地将修改后的对象重新放入MapState中。

下面是一个简单的代码示例，演示了如何在Apache Flink中使用MapState并手动更新存储的对象：

import org.apache.flink.api.common.functions.RichMapFunction;
import org.apache.flink.api.common.state.MapState;
import org.apache.flink.api.common.state.MapStateDescriptor;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;

public class MapStateExample {

    public static void main(String[] args) throws Exception {
        // 创建执行环境
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

        // 设置并行度为1，方便观察结果
        env.setParallelism(1);

        // 创建一个包含String作为键和自定义对象作为值的MapStateDescriptor
        MapStateDescriptor mapStateDescriptor =
                new MapStateDescriptor<>("customObjects", TypeInformation.of(String.class), TypeInformation.of(CustomObject.class));

        // 从数据流中映射出自定义对象，并更新MapState中存储的对象
        env.fromElements("key")
                .map(new UpdateMapState(mapStateDescriptor))
                .print();

        // 执行任务
        env.execute("MapState Example");
    }

    public static class UpdateMapState extends RichMapFunction {
        private MapState mapState;

        private final MapStateDescriptor mapStateDescriptor;

        public UpdateMapState(MapStateDescriptor mapStateDescriptor) {
            this.mapStateDescriptor = mapStateDescriptor;
        }

        @Override
        public void open(Configuration parameters) throws Exception {
            // 初始化MapState
            mapState = getRuntimeContext().getMapState(mapStateDescriptor);
        }

        @Override
        public String map(String key) throws Exception {
            // 从MapState中获取存储的对象
            CustomObject object = mapState.get(key);
            if (object == null) {
                object = new CustomObject();
            }

            // 修改对象的属性
            object.setProperty("new value");

            // 将修改后的对象重新放入MapState中
            mapState.put(key, object);

            return "Updated object: " + object;
        }
    }

    public static class CustomObject {
        private String property;

        public String getProperty() {
            return property;
        }

        public void setProperty(String property) {
            this.property = property;
        }

        @Override
        public String toString() {
            return "CustomObject{" +
                    "property='" + property + '\'' +
                    '}';
        }
    }
}

在上面的示例中，我们定义了一个UpdateMapState函数，它是一个RichMapFunction，用于更新MapState中存储的自定义对象。在map方法中，我们首先从MapState中获取存储的对象，然后修改对象的属性，并将修改后的对象重新放入MapState中。