我们在从Web API返回的模型对象上使用JAXB注释,我们希望数据本地化,并根据用户偏好格式化其他值(即度量与法规)。我们通过向Marshaller添加自定义适配器来实现这一点。
Marshaller marshaller = jc.createMarshaller();
marshaller.setAdapter(NumberPersonalizedXmlAdapter.class,
new NumberPersonalizedXmlAdapter(locale);
marshaller.marshal(expected, writer);
尝试最简单的方法,我只从HTTP请求标头中获取Locale,并将其提供给MessageBodyWriter类中的Marshaller。
我考虑过扩展默认注册的提供程序,如XMLRootElementProvider,但意识到它们大多是最终的,所以我放弃了这种方法。无论如何,我至少需要扩展10门课,所以这并不理想。
有人知道如何最好地让MessageBodyWriter中的整理器为每个请求设置客户适配器吗?我确信这与ContextResolver有关。
为封送编写ContextResolver会产生比编写MessageBodyWriter更干净、更合适的解决方案。所有JAXB类都使用Providers.getContextResolver方法来获取整理程序。我提供了我的自定义ContextResolver,并且我有i18n响应。
@Provider
@Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
public class JaxbPersonalizerContextResolver implements ContextResolver<Marshaller> {
private HttpHeaders requestHeaders;
public JaxbPersonalizerContextResolver(@Context HttpHeaders requestHeaders) {
this.requestHeaders = requestHeaders;
}
@Override
public Marshaller getContext(Class<?> type) {
Locale locale = If.first(this.requestHeaders.
getAcceptableLanguages(), Locale.US);
NumberFormat formatter = NumberFormat.getNumberInstance(locale);
formatter.setMaximumFractionDigits(1);
Marshaller marshaller;
try {
JAXBContext jc = JAXBContext.newInstance(type);
marshaller = jc.createMarshaller();
} catch (JAXBException e) {
throw new RuntimeException(e);
}
marshaller.setAdapter(QuantityXmlAdapter.class,
new QuantityXmlAdapter.Builder().locale(locale).build());
marshaller.setAdapter(NumberPersonalizedXmlAdapter.class,
new NumberPersonalizedXmlAdapter.Builder().
formatter(formatter).build());
return marshaller;
}
}
JSON没有本地化,经过一些调查,我意识到使用的是Jackson JSON库,而不是与Jersey库一起分发的JAXBJSONElementProvider。我删除了web.xml中的POJOMappingFeature配置,并本地化了JSON,但它不如Jackson JSON好。
一个非常干净的解决方案,它让我认为JAX-RS和Jersey实现做得非常好。
我解决了编写自己的MessageBodyWriter的问题,它接收注入构造函数的HttpHeaders,稍后在编写响应时使用。我将包括整个班级,因为它没有那么大。
@Produces(MediaType.APPLICATION_XML)
@Provider
public class JaxbPersonalizationProvider implements MessageBodyWriter<Object> {
private HttpHeaders requestHeaders;
private Providers providers;
public JaxbPersonalizationProvider(@Context HttpHeaders requestHeaders, @Context Providers providers) {
this.requestHeaders = requestHeaders;
this.providers = providers;
}
@Override
public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
return type.getAnnotation(XmlRootElement.class) != null && mediaType.equals(MediaType.APPLICATION_XML_TYPE);
}
@Override
public long getSize(Object t, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
return -1;
}
@Override
public void writeTo(Object t, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType,
MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException,
WebApplicationException {
Locale locale = If.first(this.requestHeaders.getAcceptableLanguages(), Locale.US);
NumberFormat formatter = NumberFormat.getNumberInstance(locale);
formatter.setMaximumFractionDigits(1);
Marshaller marshaller;
try {
JAXBContext jc = JAXBContext.newInstance(TrackInfo.class);
marshaller = jc.createMarshaller();
marshaller.setAdapter(QuantityXmlAdapter.class, new QuantityXmlAdapter.Builder().locale(locale).build());
marshaller.setAdapter(NumberPersonalizedXmlAdapter.class, new NumberPersonalizedXmlAdapter.Builder()
.formatter(formatter).build());
marshaller.marshal(t, entityStream);
} catch (JAXBException e) {
throw new RuntimeException(e);
}
}
}
它生成了这个默认语言环境为en-US:的xml摘录
<display lang="en_US">
<value>3,286.1</value>
</display>
当fr-fr的区域设置在标题中发送时,这个xml摘录:
<display lang="fr_FR">
<value>3 286,1</value>
</display>
这种方法仍然不理想,因为我现在需要为JSON编写一个类似的MessageBodyWriter,或者为此MessageBodyWriter添加JSON支持。此外,我假设默认的JAXB提供者正在进行一些我没有利用的调整。
MessageBodyWriter
是这个用例的正确方法。我建议将以下字段添加到您的MessageBodyWriter
:
@javax.ws.rs.core.Context
protected Providers providers;
然后使用它访问JAXBContext以创建Marshaller
public void writeTo(DataObject dataObject, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> multivaluedMap, OutputStream outputStream) throws IOException, WebApplicationException {
JAXBContext jaxbContext = null;
ContextResolver<JAXBContext> resolver = providers.getContextResolver(JAXBContext.class, arg3);
if(null != resolver) {
jaxbContext = resolver.getContext(type);
}
if(null == jaxbContext) {
jaxbContext = JAXBContext.newInstance(type);
}
Marshaller marshaller = jaxbContext.createMarshaller();
}
相关示例
- 在JPA/JAX-RSWeb服务中验证JAXBElement