java.lang.ClassCastException：java.util.LinkedHashMap 无法转换为 com.testing.models.Account

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.testing.models.Account

提问by Passionate Engineer

I'm getting below error:

我收到以下错误：

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.testing.models.Account

with below code

用下面的代码

final int expectedId = 1;

Test newTest = create();

int expectedResponseCode = Response.SC_OK;

ArrayList<Account> account = given().when().expect().statusCode(expectedResponseCode)
    .get("accounts/" + newTest.id() + "/users")
    .as(ArrayList.class);
assertThat(account.get(0).getId()).isEqualTo(expectedId);

Is there a reason why I cannot do get(0)?

有什么我不能做的原因get(0)吗？

采纳答案by Mark Peters

The issue's coming from Hymanson. When it doesn't have enough information on what class to deserialize to, it uses LinkedHashMap.

问题来自Hyman逊。当它没有关于要反序列化为哪个类的足够信息时，它使用LinkedHashMap.

Since you're not informing Hymanson of the element type of your ArrayList, it doesn't know that you want to deserialize into an ArrayListof Accounts. So it falls back to the default.

既然你不通知你的元素类型的Hyman逊ArrayList，它不知道你要反序列化到ArrayList的Account秒。所以它回退到默认值。

Instead, you could probably use as(JsonNode.class), and then deal with the ObjectMapperin a richer manner than rest-assured allows. Something like this:

相反，您可能可以使用as(JsonNode.class), 然后ObjectMapper以比放心允许的更丰富的方式处理 。像这样的东西：

ObjectMapper mapper = new ObjectMapper();

JsonNode accounts = given().when().expect().statusCode(expectedResponseCode)
    .get("accounts/" + newClub.getOwner().getCustId() + "/clubs")
    .as(JsonNode.class);


//Hymanson's use of generics here are completely unsafe, but that's another issue
List<Account> accountList = mapper.convertValue(
    accounts, 
    new TypeReference<List<Account>>(){}
);

assertThat(accountList.get(0).getId()).isEqualTo(expectedId);

回答by nurb

I had a similar exception (but different problem) - java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to org.bson.Document, and fortunately it's solved easier:

我有一个类似的异常（但不同的问题） - java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to org.bson.Document，幸运的是它更容易解决：

Instead of

代替

List<Document> docs = obj.get("documents");
Document doc = docs.get(0)

which gives error on second line, One can use

在第二行给出错误，可以使用

List<Document> docs = obj.get("documents");
Document doc = new Document(docs.get(0));

回答by user2578871

Try the following:

请尝试以下操作：

POJO pojo = mapper.convertValue(singleObject, POJO.class);

or:

或者：

List<POJO> pojos = mapper.convertValue(
    listOfObjects,
    new TypeReference<List<POJO>>() { });

See conversion of LinkedHashMapfor more information.

有关更多信息，请参阅LinkedHashMap 的转换。

回答by Himadri Pant

The way I could mitigate the JSON Array to collection of LinkedHashMap objectsproblem was by using CollectionTyperather than a TypeReference. This is what I did and worked:

我可以减轻JSON 数组到 LinkedHashMap 对象集合问题的方法是使用CollectionType而不是 TypeReference. 这就是我所做的和工作的：

public <T> List<T> jsonArrayToObjectList(String json, Class<T> tClass) throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    CollectionType listType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, tClass);
    List<T> ts = mapper.readValue(json, listType);
    LOGGER.debug("class name: {}", ts.get(0).getClass().getName());
    return ts;
}

---

---

Using the TypeReference, I was still getting an ArrayList of LinkedHashMaps, i.e. does not work:

使用TypeReference，我仍然得到 LinkedHashMaps 的 ArrayList，即不起作用：

public <T> List<T> jsonArrayToObjectList(String json, Class<T> tClass) throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    List<T> ts = mapper.readValue(json, new TypeReference<List<T>>(){});
    LOGGER.debug("class name: {}", ts.get(0).getClass().getName());
    return ts;
}

回答by Mohamed Farghaly

I have this method for deserializing an XML and converting the type:

我有这种反序列化 XML 和转换类型的方法：

public <T> Object deserialize(String xml, Class objClass ,TypeReference<T> typeReference ) throws IOException {
    XmlMapper xmlMapper = new XmlMapper();
    Object obj = xmlMapper.readValue(xml,objClass);
    return  xmlMapper.convertValue(obj,typeReference );   
}

and this is the call:

这是电话：

List<POJO> pojos = (List<POJO>) MyUtilClass.deserialize(xml, ArrayList.class,new TypeReference< List< POJO >>(){ });