【发布时间】：2015-03-29 04:16:25
【问题描述】：
我有一个使用 Jersey 2.6 框架运行 servlet 的 Tomcat 服务器。在 servlet 中，我将 Jackson 用于 JSON POJO 编组。我最近了解了 Moxy，并正在尝试改用它，因为它似乎是 Jersey 的首选。
目前，我的 POM 中有以下内容：
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-moxy</artifactId>
<version>2.6</version>
</dependency>
我的 RESTful 服务之一如下：
@GET
@Path("threatSeverities")
@Produces(MediaType.APPLICATION_JSON)
public List<String> getThreatSeverities() {
return dc.selectAllSeverities();
}
这对杰克逊很有效。当我更改为 Moxy 时，单元测试如下：
@Test
public void testThreatSeverities() {
final Response response = target("threatSeverities").request().get();
List<String> severities = response.readEntity(new GenericType<List<String>> () {});
assertNotNull(severities);
}
会产生以下错误：
org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyReader not found for media type=text/plain, type=interface java.util.List, genericType=java.util.List<java.lang.String>.
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.aroundReadFrom(ReaderInterceptorExecutor.java:225)
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor.proceed(ReaderInterceptorExecutor.java:149)
at org.glassfish.jersey.message.internal.MessageBodyFactory.readFrom(MessageBodyFactory.java:1124)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:853)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:812)
at org.glassfish.jersey.client.ClientResponse.readEntity(ClientResponse.java:377)
at org.glassfish.jersey.client.InboundJaxrsResponse$2.call(InboundJaxrsResponse.java:122)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:228)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:398)
at org.glassfish.jersey.client.InboundJaxrsResponse.readEntity(InboundJaxrsResponse.java:119)
at com.hp.it.scv.mobile.rest.RestTest.testThreatSeverities(RestTest.java:85)
at (... truncated)
有趣的事情要注意，即使控制器方法 getThreatSeverities 有一个 @Produces(MediaType.APPLICATION_JSON)，似乎 Moxy（或其他我不知道的东西）正在将响应的 Content-Type 标头更改为 @ 987654328@ 在单元测试中。这一切都没有发生在杰克逊身上。
还有一点需要注意，这似乎是 List<String> 对象所特有的。 Moxy 可以毫无问题地编组 POJO 列表。
- Moxy 本身是否支持将
List<String>对象编组为 JSON 字符串？似乎答案是否定的。我在网上找不到确切的答案。我想知道是否需要为List<String>对象编写自己的MessageBodyReader和MessageBodyWriter。 - 有人知道在使用 Moxy 时可以将
Content-Type标头更改为text/plain吗？我怀疑是 Moxy，可能是因为它发现我正在尝试返回一个简单的字符串列表。
更新（2015 年 2 月 2 日）：
正如 peeskillet 所指出的，返回的响应是 HTTP 500。我能够从响应中提取堆栈跟踪并得到以下信息：
Stack trace: javax.ws.rs.WebApplicationException: HTTP 500 Internal Server Error
at org.eclipse.persistence.jaxb.rs.MOXyJsonProvider.writeTo(MOXyJsonProvider.java:810)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.invokeWriteTo(WriterInterceptorExecutor.java:263)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor$TerminalWriterInterceptor.aroundWriteTo(WriterInterceptorExecutor.java:250)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.server.internal.JsonWithPaddingInterceptor.aroundWriteTo(JsonWithPaddingInterceptor.java:103)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.server.internal.MappableExceptionWrapperInterceptor.aroundWriteTo(MappableExceptionWrapperInterceptor.java:88)
at org.glassfish.jersey.message.internal.WriterInterceptorExecutor.proceed(WriterInterceptorExecutor.java:162)
at org.glassfish.jersey.message.internal.MessageBodyFactory.writeTo(MessageBodyFactory.java:1154)
at org.glassfish.jersey.server.ServerRuntime$Responder.writeResponse(ServerRuntime.java:571)
at org.glassfish.jersey.server.ServerRuntime$Responder.processResponse(ServerRuntime.java:378)
at org.glassfish.jersey.server.ServerRuntime$Responder.process(ServerRuntime.java:368)
at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:262)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:319)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:236)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1028)
at org.glassfish.jersey.grizzly2.httpserver.GrizzlyHttpContainer.service(GrizzlyHttpContainer.java:363)
at org.glassfish.grizzly.http.server.HttpHandler$1.run(HttpHandler.java:217)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Unknown Source)
Caused by: javax.xml.bind.MarshalException - with linked exception:
[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project. For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.]
at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:403)
at org.eclipse.persistence.jaxb.rs.MOXyJsonProvider.writeTo(MOXyJsonProvider.java:808)
... 25 more
Caused by: Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project. For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.
at org.eclipse.persistence.exceptions.XMLMarshalException.marshalException(XMLMarshalException.java:97)
at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:911)
at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:848)
at org.eclipse.persistence.jaxb.JAXBMarshaller.marshal(JAXBMarshaller.java:401)
... 26 more
Caused by: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class java.lang.String was not found in the project. For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.
at org.eclipse.persistence.exceptions.XMLMarshalException.descriptorNotFoundInProject(XMLMarshalException.java:139)
at org.eclipse.persistence.internal.oxm.Context$ContextState.getSession(Context.java:143)
at org.eclipse.persistence.oxm.XMLContext$XMLContextState.getSession(XMLContext.java:787)
at org.eclipse.persistence.oxm.XMLContext$XMLContextState.getSession(XMLContext.java:1)
at org.eclipse.persistence.internal.oxm.Context.getSession(Context.java:451)
at org.eclipse.persistence.oxm.XMLContext.getSession(XMLContext.java:356)
at org.eclipse.persistence.oxm.XMLContext.getSession(XMLContext.java:1)
at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:568)
at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:1096)
at org.eclipse.persistence.internal.oxm.XMLMarshaller.marshal(XMLMarshaller.java:869)
... 28 more
从Exception Description: A descriptor for class java.lang.String was not found in the project. 看来，如果不手动编码，就无法实现从List<String> 到 JSON 编组。
【问题讨论】：
-
异常看起来在客户端。我没有机会测试它，所以我不确定你的第一个问题，但对于第二个问题，看起来你正在使用 JerseyTest 框架。如果您使用的是 grizzley 容器。如果有 500，它将被映射到一个灰熊响应，即
text/plain。您可以从响应中获取状态码以查看是否为 500 -
好点。我刚刚添加了
System.out.println(response.getHeaderString("Content-type")); System.out.println(response.getStatus());并返回了text-plain 500。这就回答了第二个问题。我仍然想知道为什么 Moxy 不能简单地将List<String>转换为 JSON。 -
moxy 可以做到，我有一些类似的奇怪错误，原因似乎并不相关。请尝试在您的测试中包含 .request(MediaType.APPLICATION_JSON_TYPE)