如何自定义JAXB对象列表到JSON的序列化？ [英] How can I customize serialization of a list of JAXB objects to JSON?
问题描述
我正在使用Jersey为服务器组件创建REST Web服务。
I'm using Jersey to create a REST web service for a server component.
我要在列表中序列化的JAXB注释对象如下所示：
The JAXB-annotated object I want to serialize in a list looks like this:
@XmlRootElement(name = "distribution")
@XmlType(name = "tDistribution", propOrder = {
"id", "name"
})
public class XMLDistribution {
private String id;
private String name;
// no-args constructor, getters, setters, etc
}
我有一个REST资源来检索一个看起来像这样的发行版：
I have a REST resource to retrieve one distribution which looks like this:
@Path("/distribution/{id: [1-9][0-9]*}")
public class RESTDistribution {
@GET
@Produces("application/json")
public XMLDistribution retrieve(@PathParam("id") String id) {
return retrieveDistribution(Long.parseLong(id));
}
// business logic (retrieveDistribution(long))
}
我还有一个REST资源来检索所有发行版的列表，如下所示：
I also have a REST resource to retrieve a list of all distributions, which looks like this:
@Path("/distributions")
public class RESTDistributions {
@GET
@Produces("application/json")
public List<XMLDistribution> retrieveAll() {
return retrieveDistributions();
}
// business logic (retrieveDistributions())
}
<我使用ContextResolver来自定义JAXB序列化，目前配置如下：
I use a ContextResolver to customize JAXB serialization, which is currently configured like this:
@Provider
@Produces("application/json")
public class JAXBJSONContextResolver implements ContextResolver<JAXBContext> {
private JAXBContext context;
public JAXBJSONContextResolver() throws Exception {
JSONConfiguration.MappedBuilder b = JSONConfiguration.mapped();
b.nonStrings("id");
b.rootUnwrapping(true);
b.arrays("distribution");
context = new JSONJAXBContext(b.build(), XMLDistribution.class);
}
@Override
public JAXBContext getContext(Class<?> objectType) {
return context;
}
}
两种REST资源都可以使用，以及上下文解析器。这是第一个输出的示例：
Both REST resources work, as well as the context resolver. This is an example of output for the first one:
// path: /distribution/1
{"id":1,"name":"Example Distribution"}
这正是我想要的。这是列表输出的示例：
Which is exactly what I want. This is an example of output for the list:
// path: /distributions
{"distribution":[{"id":1,"name":"Sample Distribution 1"},{"id":2,"name":"Sample Distribution 2"}]}
这不是我想要的。
我不明白为什么有一个封闭的发布标签。我想在上下文解析器中使用 .rootUnwrapping（true）删除它，但显然只删除了另一个封闭标记。这是输出 .rootUnwrapping（false）：
I don't understand why there is an enclosing distribution tag there. I wanted to remove it with .rootUnwrapping(true) in the context resolver, but apparently that only removes another enclosing tag. This is the output with .rootUnwrapping(false):
// path: /distribution/1
{"distribution":{"id":1,"name":"Example Distribution"}} // not ok
// path: /distributions
{"xMLDistributions":{"distribution":[{"id":1,"name":"Sample Distribution 1"},{"id":2,"name":"Sample Distribution 2"}]}}
我还必须配置 .arrays（distribution）总是得到一个JSON数组，即使只有一个元素。
I also had to configure .arrays("distribution") to always get a JSON array, even with only one element.
理想情况下，我想把它作为输出：
Ideally, I'd like to have this as an output:
// path: /distribution/1
{"id":1,"name":"Example Distribution"} // currently works
// path: /distributions
[{"id":1,"name":"Sample Distribution 1"},{"id":2,"name":"Sample Distribution 2"}]
我试图返回列表< XMLDistribution> ， XMLDistributionList （列表中的包装）， XMLDistribution [] ，但我找不到aw ay以我所需的格式获得一个简单的JSON分发数组。
I tried to return a List<XMLDistribution>, a XMLDistributionList (wrapper around a list), a XMLDistribution[], but I couldn't find a way to get a simple JSON array of distributions in my required format.
我还尝试了 JSONConfiguration.natural（）返回的其他符号， JSONConfiguration.mappedJettison（）等，并且无法获得类似于我需要的任何内容。
I also tried the other notations returned by JSONConfiguration.natural(), JSONConfiguration.mappedJettison(), etc, and couldn't get anything resembling what I need.
有没有人知道是否可以配置JAXB来执行此操作？
Does anyone know if it is possible to configure JAXB to do this?
推荐答案
我找到了一个解决方案：替换JAXB JSON序列化程序，具有像Jackson这样表现更好的JSON序列化程序。简单的方法是使用jackson-jaxrs，它已经为你完成了它。该课程是JacksonJsonProvider。您所要做的就是编辑项目的web.xml，以便Jersey（或其他JAX-RS实现）扫描它。以下是您需要添加的内容：
I found a solution: replace the JAXB JSON serializer with a better behaved JSON serializer like Jackson. The easy way is to use jackson-jaxrs, which has already done it for you. The class is JacksonJsonProvider. All you have to do is edit your project's web.xml so that Jersey (or another JAX-RS implementation) scans for it. Here's what you need to add:
<init-param>
<param-name>com.sun.jersey.config.property.packages</param-name>
<param-value>your.project.packages;org.codehaus.jackson.jaxrs</param-value>
</init-param>
这就是它的全部内容。 Jackson将用于JSON序列化，它的工作方式与列表和数组的预期方式相同。
And that's all there is to it. Jackson will be used for JSON serialization, and it works the way you expect for lists and arrays.
更长的方法是编写自己的自定义MessageBodyWriter，以生成application / json。下面是一个例子：
The longer way is to write your own custom MessageBodyWriter registered to produce "application/json". Here's an example:
@Provider
@Produces("application/json")
public class JsonMessageBodyWriter implements MessageBodyWriter {
@Override
public long getSize(Object obj, Class type, Type genericType,
Annotation[] annotations, MediaType mediaType) {
return -1;
}
@Override
public boolean isWriteable(Class type, Type genericType,
Annotation annotations[], MediaType mediaType) {
return true;
}
@Override
public void writeTo(Object target, Class type, Type genericType,
Annotation[] annotations, MediaType mediaType,
MultivaluedMap httpHeaders, OutputStream outputStream)
throws IOException {
new ObjectMapper().writeValue(outputStream, target);
}
}
您需要确保您的web.xml包含该包，至于上面的现成解决方案。
You'll need to make sure your web.xml includes the package, as for the ready-made solution above.
无论哪种方式：瞧！你会看到正确形成的JSON。
Either way: voila! You'll see properly formed JSON.
你可以从这里下载Jackson：
http://jackson.codehaus.org/
You can download Jackson from here: http://jackson.codehaus.org/
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