java - Jersey 客户端无法反序列化 XML 输出 : message body reader was not found

Question

我正在使用旧的 com.sun.jersey.jersey-client@1.19.4 库来调用私有(private)第三方 REST 服务上的 POST，使用 application/x-www-form-urlencoded 内容类型。

一切似乎都按预期运行，但是，响应并未自动反序列化到我的 POJO。异常是 ClientHandlerException，声称该 POJO 没有消息正文解析器。

可用的默认提供程序有:

com.sun.jersey.core.impl.provider.entity.FormProvider com.sun.jersey.core.impl.provider.entity.StringProvider com.sun.jersey.core.impl.provider.entity.ByteArrayProvider com.sun.jersey.core.impl.provider.entity.FileProvider com.sun.jersey.core.impl.provider.entity.InputStreamProvider com.sun.jersey.core.impl.provider.entity.DataSourceProvider com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General com.sun.jersey.core.impl.provider.entity.ReaderProvider com.sun.jersey.core.impl.provider.entity.DocumentProvider com.sun.jersey.core.impl.provider.entity.SourceProvider$StreamSourceReader com.sun.jersey.core.impl.provider.entity.SourceProvider$SAXSourceReader com.sun.jersey.core.impl.provider.entity.SourceProvider$DOMSourceReader com.sun.jersey.json.impl.provider.entity.JSONJAXBElementProvider$General com.sun.jersey.json.impl.provider.entity.JSONArrayProvider$General com.sun.jersey.json.impl.provider.entity.JSONObjectProvider$General com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General com.sun.jersey.core.impl.provider.entity.XMLRootObjectProvider$General com.sun.jersey.core.impl.provider.entity.EntityHolderReader com.sun.jersey.json.impl.provider.entity.JSONRootElementProvider$General com.sun.jersey.json.impl.provider.entity.JSONListElementProvider$General com.sun.jersey.json.impl.provider.entity.JacksonProviderProxy

预期的第三方服务XML输出模板:

<foobar>
    <foo>Foooooooo</foo>
    <bar>Barrrrrrr</bar>
</foobar>

POJO:

@XmlRootElement(name = "foobar")
@XmlAccessorType(XmlAccessType.FIELD)
public class Foobar {

    @XmlElement(name = "foo")
    private String foo;

    @XmlElement(name = "bar")
    private String bar;

    public String getFoo() {
        return foo;
    }

    public void setFoo(String foo) {
        this.foo = foo;
    }

    public String getBar() {
        return bar;
    }

    public void setBar(String bar) {
        this.bar = bar;
    }

}

请求:

MultivaluedMap parameters = new MultivaluedMapImpl();

parameters.add(...);

Foobar response = client.resource(URL)
        .type(MediaType.APPLICATION_FORM_URLENCODED)
        .accept(MediaType.APPLICATION_XML)
        .post(Foobar.class, parameters);

异常(exception):

Exception in thread "main" com.sun.jersey.api.client.ClientHandlerException: A message body reader for Java class foo.bar.Foobar, and Java type class foo.bar.Foobar, and MIME media type text/html; charset=UTF-8 was not found at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:630) at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:586) at com.sun.jersey.api.client.WebResource.handle(WebResource.java:686) at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) at com.sun.jersey.api.client.WebResource$Builder.post(WebResource.java:570) at foo.bar.Main.jerseySample(Main.java:103) at foo.bar.Main.main(Main.java:109)

使用 JAXB 解码器反序列化 XML 字符串效果很好，但是 Jersey 无法单独完成此操作(可能需要借助 XMLJAXBElementProvider、XMLRootElementProvider、 XMLRootObjectProvider？)。这是怎么回事？

Answer 1

我发现解决此问题的最简洁方法是创建自定义 MessageBodyReader。

public static class FoobarMessageBodyReader implements MessageBodyReader<Foobar> {

    private Unmarshaller unmarshaller;

    public RespostaIncluirMessageBodyReader() throws JAXBException {
        unmarshaller = JAXBContext.newInstance(Foobar.class).createUnmarshaller();
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type.isAssignableFrom(Foobar.class);
    }

    @Override
    public Foobar readFrom(Class<Foobar> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, String> httpHeaders, InputStream entityStream) throws IOException, WebApplicationException {
        try {
            return (Foobar) unmarshaller.unmarshal(entityStream);
        }
        catch (JAXBException e) {
            throw new IOException("Could not unmarshal the XML output", e);
        }
    }

}

...并将其添加到客户端配置中，如下所示:

ClientConfig clientConfig = new DefaultClientConfig();
clientConfig.getClasses().add(FoobarMessageBodyReader.class);
Client client = Client.create(clientConfig);

您现在应该已成功反序列化您的对象。