A SimpleDataStore

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

public interface DataStore {
 
    /**
     * return a snapshot value of componentName
     */
    Map<String,Object> get(String componentName);
 
    Object get(String componentName, String key);
 
    void put(String componentName, String key, Object value);
 
    void remove(String componentName, String key);
 
}

public class SimpleDataStore implements DataStore {
 
    // <组件类名或标识, <数据名, 数据值>>
    private ConcurrentMap<String, ConcurrentMap<String, Object>> data =
        new ConcurrentHashMap<String, ConcurrentMap<String,Object>>();
 
    public Map<String, Object> get(String componentName) {
        ConcurrentMap<String, Object> value = data.get(componentName);
        if(value == null) return new HashMap<String, Object>();
 
        return new HashMap<String, Object>(value);
    }
 
    public Object get(String componentName, String key) {
        if (!data.containsKey(componentName)) {
            return null;
        }
        return data.get(componentName).get(key);
    }
 
    public void put(String componentName, String key, Object value) {
        Map<String, Object> componentData = data.get(componentName);
        if(null == componentData) {
            data.putIfAbsent(componentName, new ConcurrentHashMap<String, Object>());
            componentData = data.get(componentName);
        }
        componentData.put(key, value);
    }
 
    public void remove(String componentName, String key) {
        if (!data.containsKey(componentName)) {
            return;
        }
        data.get(componentName).remove(key);
    }
 
}