如何在Spring中将多个地图合并成一个 [英] How to merge multiple maps into one in Spring

问题描述

我在我的上下文文件中定义了几个地图。有没有办法将这些地图组合成一个包含所有条目的地图，而不需要编写Java代码（而不使用嵌套的地图）？我正在寻找相当于Map m = new HashMap（）; m.putAll（carMap）; m.putAll（bikeMap）;
似乎应该有一种方法在Spring上下文文件中执行此操作，但是在util：map上的Spring 3.0参考文档部分并不涵盖此用例。

 <！ - 我想创建一个id为车辆的地图，其中包含其他地图的所有条目 - > 
 
< util：map id =cars> 
< entry key =groceryGettervalue-ref =impreza/> 
< / util：map> 
 
< util：map id =bicycles> 
< entry key =commuterBikevalue-ref =schwinn/> 
< / util：map> 
  

解决方案

使用集合合并概念可以逐步合并。我在我的项目中使用了这一点，以合并列表，但也可以扩展到合并地图。

例如

 < bean id =commonMap
 class =org.springframework.beans.factory.config.MapFactoryBean> 
< property name =sourceMap> 
< map> 
< entry key =1value =one/> 
< entry key =2value =two/> 
< / map> 
< / property> 
< / bean> 
< bean id =firstMap
父=commonMap
 class =org.springframework.beans.factory.config.MapFactoryBean> 
< property name =sourceMap> 
< map merge =true> 
< entry key =3value =three/> 
< entry key =4value =four/> 
< / map> 
< / property> 
< / bean> 
  

第二个地图定义与第一个地图定义的关联是通过 < bean> 节点中的父属性，第一个地图中的条目与第二个地图中的条目合并，使用< map> 节点上合并属性。

I have several maps defined in my context file. Is there a way to combine those maps into one map that contains all of their entries, without writing Java code (and without using nested maps)? I'm looking for the equivalent of Map m = new HashMap(); m.putAll(carMap); m.putAll(bikeMap); Seems like there should be a way to do this in Spring context file, but the Spring 3.0 reference doc section on util:map doesn't cover this use case.

<!-- I want to create a map with id "vehicles" that contains all entries of the other maps -->

<util:map id="cars">
    <entry key="groceryGetter" value-ref="impreza"/>
</util:map>

<util:map id="bicycles">
    <entry key="commuterBike" value-ref="schwinn"/>
</util:map>

解决方案

Using collection merging concept in Spring, multiple beans like these can be merged incrementally. I used this in my project to merge lists , but can be extended to merge maps as well.

E.g.

<bean id="commonMap" 
      class="org.springframework.beans.factory.config.MapFactoryBean">
    <property name="sourceMap">
        <map>
            <entry key="1" value="one"/>
            <entry key="2" value="two"/>
        </map>
    </property>
</bean>
<bean id="firstMap" 
      parent="commonMap" 
      class="org.springframework.beans.factory.config.MapFactoryBean">
    <property name="sourceMap">
        <map merge="true">
            <entry key="3" value="three"/>
            <entry key="4" value="four"/>
        </map>
    </property>
</bean>

The association of the second map definition with the first one is done through the parent attribute on the <bean> node and the entries in the first map are merged with those in the second using the merge attribute on the <map> node.

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