Resteasy将列表转换为LinkedHashMap [英] Resteasy converting List to LinkedHashMap

问题描述

我正在使用resteasy在一些宁静的Web服务之间发送键/值对.

I am using resteasy to send key/value pairs in between some restful web-services.

要发布这些对的列表，我要使用此代码段

to post a list of these pairs i use this snippet

List<Pair> pairs = new ArrayList<>();
pairs.add(new Pair("name", "Arnold"));
pairs.add(new Pair("age", "20"));

ResteasyClient resteasyClient = getClient();
ResteasyWebTarget target = resteasyClient.target(targetURI);
Invocation.Builder request = target.request();
request.post(Entity.entity(entity, MediaType.APPLICATION_JSON_TYPE));

Pair只是带有

public String key,
public String value 
default constructor 
(key,value) constructor

目标资源通过以下方式接收该信息:

The target resource an receive this via:

 @POST
 @Path("/metadata")
 @Consumes(MediaType.APPLICATION_JSON)
 public Response postMetadata(List<Pair> properties) {...

jax-rs资源可以正确读取列表.

the jax-rs resource can read the List correctly.

现在另一种方法是问题:

Now the other way is the Problem:

检索资源定义为:

@GET
@Path("/getUrl.../{id}")
@Produces(MediaType.APPLICATION_JSON)
public Response getMetadata(@PathParam("id") String id) {
data_from_hibernate = em.find(id);
...
List<Pair> properties = new ArrayList<>();
//fill List from data
return Response.ok().entity(properties).build();

客户端是:

Response response = request.get("http://getUrl.../"+id);
List<Pair> properties = response.readEntity(List.class);

logger.info("got properties != null? " +(properties!=null));
logger.info("size: "+properties.size());
logger.info("[0]" + properties.get(0));
logger.info("type: "+properties.get(0).getClass().getName());

列表不为空；

大小正确；

get(0)确实以奇怪的格式输出:[0] {"name":"value"};

get(0) does output in a strange format: [0]{"name": "value"};

其次是奇怪格式的原因:异常告诉我:

this is followed by the strange format's reason: an Exception tells me that:

java.util.LinkedHashMap无法强制转换为Pair

java.util.LinkedHashMap cannot be cast to Pair

此时properties是LinkedHashMap是什么，或者更确切地说是:LinkedHashMaps列表?

How is properties a LinkedHashMap at this point, or rather: a List of LinkedHashMaps?

推荐答案

在没有类型信息的情况下(当您使用readEntity时)，Jackson(底层反序列化器)会将任意JSON对象转换为LinkedHashMap.

Without type information (when you use readEntity), Jackson (the underlying deserializer) will convert arbitrary JSON objects to LinkedHashMap.

使用readEntity时，通过使用 GenericType .

When using readEntity, you provide generic type information by using GenericType.

List<Pair> properties = response.readEntity(new GenericType<List<Pair>>(){});

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