java 使用 spring-hateoas 反序列化包含（_links 和 _embedded）的 JSON
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Deserialize JSON containing (_links and _embedded) using spring-hateoas
提问by Heyjojo
I am trying to invoque very simple json webservices that return data of this form:
我正在尝试调用返回这种形式的数据的非常简单的 json webservices：
{
"_embedded": {
"users": [{
"identifier": "1",
"firstName": "John",
"lastName": "Doe",
"_links": {
"self": {
"href": "http://localhost:8080/test/users/1"
}
}
},
{
"identifier": "2",
"firstName": "Paul",
"lastName": "Smith",
"_links": {
"self": {
"href": "http://localhost:8080/test/users/2"
}
}
}]
},
"_links": {
"self": {
"href": "http://localhost:8080/test/users"
}
},
"page": {
"size": 20,
"totalElements": 2,
"totalPages": 1,
"number": 0
}
}
As you can see, it is pretty straight forward. I have no problems parsing the links, having my POJOs extending form ResourceSupport. Here is what they look like:
如您所见，它非常简单。我解析链接没有问题，我的 POJO 扩展了 ResourceSupport。这是它们的样子：
UsersJson (the root element)
UsersJson（根元素）
public class UsersJson extends ResourceSupport {
private List<UserJson> users;
[... getters and setters ...]
}
UserJson
用户Json
public class UserJson extends ResourceSupport {
private Long identifier;
private String firstName;
private String lastName;
[... getters and setters ...]
}
The thing is that I was expecting Hymanson and spring to be smart enough to parse the _embedded property and populate my UsersJson.users attribute but it isn't.
问题是我希望 Hymanson 和 spring 足够聪明，可以解析 _embedded 属性并填充我的 UsersJson.users 属性，但事实并非如此。
I tried various things I found on the internet but the only thing I could get to work properly was to create a new class acting as an _embedded wrapper:
我尝试了在互联网上找到的各种东西，但我唯一能正常工作的方法是创建一个充当 _embedded 包装器的新类：
UsersJson (the root element)
UsersJson（根元素）
public class UsersJson extends ResourceSupport {
@JsonProperty("_embedded")
private UsersEmbeddedListJson embedded;
[... getters and setters ...]
}
Embedded "wrapper"
嵌入式“包装器”
public class UsersEmbeddedListJson extends ResourceSupport {
private List<UserJson> users;
[... getters and setters ...]
}
It works but I find it quite ugly.
它有效，但我觉得它很丑。
Yet I though the following configuration of the RestTemplate would have worked (especially when I saw EmbeddedMapper in Hymanson2HalModule), but it didn't:
然而，我虽然 RestTemplate 的以下配置会起作用（尤其是当我在 Hymanson2HalModule 中看到 EmbeddedMapper 时），但它没有：
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
mapper.registerModule(new Hymanson2HalModule());
MappingHymanson2HttpMessageConverter converter = new MappingHymanson2HttpMessageConverter();
converter.setSupportedMediaTypes(MediaType.parseMediaTypes("application/hal+json"));
converter.setObjectMapper(mapper);
RestTemplate restTemplate = new RestTemplate(Collections.singletonList(converter));
ResponseEntity<UsersJson> result = restTemplate.getForEntity("http://localhost:8089/test/users", UsersJson.class, new HashMap<String, Object>());
System.out.println(result);
Can somebody tell me what I am missing?
有人可以告诉我我缺少什么吗？
采纳答案by Heyjojo
Finally, I found a better a way to consume those application/hal+json APIs.
最后，我找到了一种更好的方式来使用那些 application/hal+json API。
Spring hateoas actually provides a client almost ready to use: org.springframework.hateoas.client.Traverson.
Spring hateoas 实际上提供了一个几乎可以使用的客户端：org.springframework.hateoas.client.Traverson。
Traverson traverson = new Traverson(new URI("http://localhost:8080/test"), MediaTypes.HAL_JSON);
TraversalBuilder tb = traverson.follow("users");
ParameterizedTypeReference<Resources<UserJson>> typeRefDevices = new ParameterizedTypeReference<Resources<UserJson>>() {};
Resources<UserJson> resUsers = tb.toObject(typeRefDevices);
Collection<UserJson> users= resUsers .getContent();
As you can see, I got rid UsersJson and UsersEmbeddedListJson.
如您所见，我摆脱了 UsersJson 和 UsersEmbeddedListJson。
Here are the maven dependencies I added
这是我添加的 maven 依赖项
<dependency>
<groupId>org.springframework.hateoas</groupId>
<artifactId>spring-hateoas</artifactId>
<version>0.19.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.plugin</groupId>
<artifactId>spring-plugin-core</artifactId>
<version>1.2.0.RELEASE</version>
</dependency>
<dependency>
<groupId>com.jayway.jsonpath</groupId>
<artifactId>json-path</artifactId>
<version>2.0.0</version>
</dependency>
回答by Whimusical
Had to add this to my DTO:
必须将此添加到我的 DTO：
@JsonProperty("_links")
public void setLinks(final Map<String, Link> links) {
links.forEach((label, link) -> add(link.withRel(label)) );
}
since ResourceSupport has no POJO standard/Json-signaled setter/constructor for links
因为 ResourceSupport 没有用于链接的 POJO 标准/Json 信号设置器/构造器
回答by k_o_
I had to extend my DTO POJO with a custom setter parsing the produced output of Spring Hateos in the REST client side by using Hymanson as mapper:
我必须使用 Hymanson 作为映射器，使用自定义 setter 扩展我的 DTO POJO，在 REST 客户端解析 Spring Hateos 的生成输出：
HREF= "href"and RELis "rel"as constants.
HREF= "href"并且REL是"rel"作为常量。
@JsonProperty("link")
public void setLink(final List<Map<String, String>> links) {
if (links != null) {
links.forEach(l ->
{
final String[] rel = new String[1];
final String[] href = new String[1];
l.entrySet().stream().filter((e) -> e.getValue() != null)
.forEach(e -> {
if (e.getKey().equals(REL)) {
rel[0] = e.getValue();
}
if (e.getKey().equals(HREF)) {
href[0] = e.getValue();
}
});
if (rel[0] != null && href[0] != null) {
add(new Link(href[0], rel[0]));
}
}
);
}
}
