Java 创建文本/纯泽西响应
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Create a text/plain Jersey response
提问by Jess
I have some code that works, but I am looking for a better way to do it. I have a RESTful web API that I want to support JSON, XML, and TEXT media types. The JSON and XML is easy with a JAXB annotated "bean" class. I just got text/plainto work, but I wish Jersey was a little more intelligent and would be able to convert a list of my beans, List<Machine>to a string using toString.
我有一些有效的代码，但我正在寻找更好的方法来做到这一点。我有一个 RESTful Web API，我希望它支持 JSON、XML 和 TEXT 媒体类型。JSON 和 XML 使用 JAXB 注释的“bean”类很容易。我只是让text/plain工作，但我希望 Jersey 更智能一点，并且能够将我的 bean 列表转换为List<Machine>使用toString.
Here is the Resource class. The JSON and XML media types use a JAXB annotated bean class. The text plain uses a custom string format (basically the stdout representation of a command).
这是资源类。JSON 和 XML 媒体类型使用 JAXB 注释 bean 类。纯文本使用自定义字符串格式（基本上是命令的标准输出表示）。
@Path("/machines")
public class MachineResource {
private final MachineManager manager;
@Inject
public MachineResource(MachineManager manager) {
this.manager = manager;
}
@GET @Path("details/")
@Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML })
public List<Machine> details() {
return manager.details();
}
@GET @Path("details/")
@Produces({ MediaType.TEXT_PLAIN })
public String detailsText() {
StringBuilder text = new StringBuilder();
for(Machine machine : manager.details()) {
text.append(machine.toString());
}
return text.toString();
}
Is there a better way to do this with Jersey automatically converting to a string, so I only have to implement one method here?(That can handle all 3 media types)
有没有更好的方法可以让 Jersey 自动转换为字符串，所以我只需要在这里实现一个方法？（可以处理所有 3 种媒体类型）
I see that I can implement a MessageBodyWriter, but that seems like a lot more trouble.
我看到我可以实现MessageBodyWriter，但这似乎更麻烦。
EDIT:
编辑：
If it matters, I am using the embedded Jetty and Jersey options.
如果重要的话，我正在使用嵌入式 Jetty 和 Jersey 选项。
Thanks!
谢谢！
采纳答案by bdoughan
Implementing a MessageBodyReader/Writerwould be what you need to do in order to do the following:
实现MessageBodyReader/Writer将是您需要做的，以便执行以下操作：
@GET @Path("details/")
@Produces({ MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML, MediaType.TEXT_PLAIN })
public List<Machine> details() {
return manager.details();
}
It's not very much code to write, and if you are able to write it generic enough you will be able to get some re-use out of it.
要编写的代码并不多，如果您能够编写足够通用的代码，您将能够对其进行重用。
回答by Jess
1. @Provider
1.@提供者
For some reason the documentation does not mention that I need to annotate the MessageBodyWriterclass with @Provider. I have done that...
出于某种原因，文档没有提到我需要MessageBodyWriter用@Provider. 我已经这样做了...
@Provider
@Produces(MediaType.TEXT_PLAIN)
public class PlainTextWriter implements MessageBodyWriter<Machine> {
... and now I see this message on start up.* (Good)
...现在我在启动时看到此消息。*（好）
INFO: Provider classes found:
class com.blah.resources.PlainTextWriter
I still get the exception,
我仍然得到例外，
SEVERE: A message body writer for Java class java.util.ArrayList,
and Java type java.util.List<com.blah.beans.Machine>,
and MIME media type text/plain was not found
- Without @Provider, you get this message on start-up:
INFO: No provider classes found.
- 如果没有@Provider，您会在启动时收到此消息：
INFO: No provider classes found.
2. Use the correct type
2.使用正确的类型
The second part is that I was not implementing for the correct type. I had a Listof beans. I assumed Jersey would be smart enough to understand how to serialize a list, but I guess it could do that in different ways. Here was my second change: (Note the addition of List)
第二部分是我没有为正确的类型实现。我有一个List豆子。我认为 Jersey 足够聪明，可以理解如何序列化列表，但我想它可以以不同的方式做到这一点。这是我的第二个更改：（注意添加了List）
@Provider
@Produces(MediaType.TEXT_PLAIN)
public class PlainTextWriter implements MessageBodyWriter<List<Machine>>
It is working now. It's pretty cool because now I have a generic plain/text implementation. I only have to implement the toPlainTextmethod of my interface for each Bean. No sweat!
它现在正在工作。这很酷，因为现在我有了一个通用的纯文本/文本实现。我只需要toPlainText为每个 Bean实现我的接口的方法。没有汗！
3. Use the correct package.
3. 使用正确的包装。
It broke again. Looking at the log I see this:
又断了。查看日志我看到了这个：
INFO: Scanning for root resource and provider classes in the packages:
com.my.project.resources
...
INFO: No provider classes found.
So I refactored my MessageBodyWriter into that package and it works again!
所以我将我的 MessageBodyWriter 重构到那个包中，它又可以工作了！
