Spring更高版本的HashMaps的LinkedCaseInsensitive地图投放问题 [英] LinkedCaseInsensitive map casting issue with HashMaps with Spring higher version

问题描述

LinkedCaseInsensitiveMap 是Spring框架的一部分，并扩展了 LinkedHashMap

The LinkedCaseInsensitiveMap is part of the Spring Framework and extends the LinkedHashMap

层次结构如下:

java.lang.Object

java.lang.Object

java.util.AbstractMap

java.util.AbstractMap

java.util.HashMap

java.util.HashMap

java.util.LinkedHashMap

java.util.LinkedHashMap

org.springframework.util.LinkedCaseInsensitiveMap

org.springframework.util.LinkedCaseInsensitiveMap

有关信息，请参阅:现在我有了以下代码:

List<HashMap<String, String>> l_lstResult = (List<HashMap<String, String>>)service.fetchRowwiseMultipleRecords(p_iQueryName, l_hmParams, userDetails);

                l_lstCityTownList = new ArrayList<String>(l_lstResult.size());

                for (int i = 0; i < l_lstResult.size(); i++) {
                    HashMap<String, String> l_hmColmnData = l_lstResult.get(i);
                    String l_sValue = l_hmColmnData.get(p_sColumnName);
                    l_lstCityTownList.add(l_sValue);
                }

l_lstResult返回一个LinkedCaseInsensitiveMap，我在 HashMap l_hmColmnData = l_lstResult.get(i);

The l_lstResult returns a LinkedCaseInsensitiveMap and i get the error in the line HashMap l_hmColmnData = l_lstResult.get(i);

java.lang.ClassCastException: org.springframework.util.LinkedCaseInsensitiveMap无法转换为 java.util.HashMap

java.lang.ClassCastException: org.springframework.util.LinkedCaseInsensitiveMap cannot be cast to java.util.HashMap

问题是我在Spring版本4.3.14.RELEASE中收到此错误，而在3.2.3RELEASE中没有错误. 3.2.3.RELEASE中允许进行此转换的规范在哪里?

The thing is i get this error with Spring version 4.3.14.RELEASE and no error in 3.2.3.RELEASE. Where is the specification in 3.2.3.RELEASE that allows this casting.

任何建议，示例都会对我有很大帮助.

Any suggestions,examples would help me a lot .

非常感谢！

推荐答案

从Spring 4.3.6.RELEASE开始，LinkedCaseInsensitiveMap不再扩展LinkedHashMap和HashMap，而仅实现Map接口.

Since Spring 4.3.6.RELEASE, LinkedCaseInsensitiveMap doesn't extend anymore LinkedHashMap and HashMap, but only implements Map interface.

API参考.

将service.fetchRowwiseMultipleRecords(p_iQueryName, l_hmParams, userDetails)强制转换为List<HashMap<String, String>>时，只是在告诉编译器信任 .但是，当要获取列表的第一个元素时，它会失败，因为它不是HashMap，而是LinkedCaseInsensitiveMap(不扩展HashMap)，不是HashMap.

When you cast service.fetchRowwiseMultipleRecords(p_iQueryName, l_hmParams, userDetails) to List<HashMap<String, String>> you're just telling the compiler to trust you. But then, when it comes to get the first element of the list, it fails because it's not a HashMap but a LinkedCaseInsensitiveMap (not extending HashMap).

这将解决您的问题

List<LinkedCaseInsensitiveMap<String>> l_lstResult = service.fetchRowwiseMultipleRecords(p_iQueryName, l_hmParams, userDetails);

l_lstCityTownList = new ArrayList<String>(l_lstResult.size());

for (int i = 0; i < l_lstResult.size(); i++) {
    LinkedCaseInsensitiveMap<String> l_hmColmnData = l_lstResult.get(i);
    String l_sValue = l_hmColmnData.get(p_sColumnName);
    l_lstCityTownList.add(l_sValue);
}

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