Marshal / Un marshal使用JAXB在Jersey JAX-RS中列出对象 [英] Marshal/Un marshal List objects in Jersey JAX-RS using JAXB

问题描述

早上好。今天早上，当我通过泽西实体提供商 MessageBodyReader 和 MessageBodyWriter 时，我遇到了以下问题。

Good Morning. Today morning when I am going through Jersey Entity providers MessageBodyReaders and MessageBodyWriters I came across the following problem.

我想写一个资源方法和客户端，它返回一个自定义对象列表，媒体类型是 application / xml 。所以我想使用JAXB（我是JAXB的新手）。我能够通过编写自己的扩展 MessageBodyReader 和 MessageBodyWriter 来实现这一目标。但我害怕跟随的方式。看看我实施的方式：

I want to write a resource method and client that returns a list of custom objects and media type is application/xml. So I would like to use JAXB (I am new to JAXB). I was able to achieve this by writing my own extended MessageBodyReader and MessageBodyWriter. But I am afraid of the way I am following. Just look at the way I implemented:

资源方法：

@Path("productlist/xml")
@GET
public RetObjects getProductsXml(){
    List<Product> pList = new ArrayList<Product>();
    pList.add(new Product("1","Dell latitude E6000",2900,500));
    pList.add(new Product("2","Xperia Z2",549,400));
    RetObjects obj = new RetObjects();
    obj.setObject(pList);
    return obj;
}

我的自定义对象：

@Entity
@Table (name="PRODUCT")
@XmlRootElement(name="product")
public class Product {

    @Id
    @Column(name = "CODE")
    private String code;
    ...
    // rest of the fields, constructors, getters and setters
 }

包装我的自定义对象列表的对象：

Object that wraps my list of custom object:

 @XmlRootElement(name = "products")
 @XmlAccessorType (XmlAccessType.FIELD)
 public class RetObjects {

     @XmlElement(name = "product")
     private List<Product> object = null;

     public List<Product> getObject() {
         return object;
     }

     public void setObject(List<Product> object) {
         this.object = object;
     }
 }

MessageBodyReader / Writer 直接使用Jaxb unmarshaller和marshaller而不是 RetObjects 对象。

MessageBodyReader/Writer are straight forward just using Jaxb unmarshaller and marshaller over the RetObjects object.

使用此实现它正如预期的那样正常工作，我能够获取 RetObjects 在客户端完美地包装产品列表。

With this implementation it is working fine as expected and i am able to fetch the RetObjects wrapping the list of Products perfectly fine at client.

这里我的问题是，在我的情况下，不是将我的产品列表包装到一个中间对象中，而是 RetObjects ，我无法直接编组和解组产品列表对象。如果我想编写另一个返回订单列表的服务，我需要用另一个中间对象包装它。实现这一目标的正确方法是什么？如果没有中间对象，我怎么能这样做？

Here my question is, instead of wrapping my List of Products into a intermediate object, RetObjects in my case, couldn't I marshal and unmarshal List of Products object directly. If I want to write another service that returns List of Orders, I need to wrap this with one more intermediate object. What is the right approach to achieve this? How could I do this without intermediate objects?

推荐答案

首先

你不需要你自己的 MessageBodyWriter / Reader 。 Jersey / JAX-RS alread对此有标准支持。我会坚持使用默认值，除非你有一个真的，非常的理由需要你自己动手。

You don't need your own MessageBodyWriter/Reader. Jersey/JAX-RS alread has standard support for this. I would stick with the default, unless you have a really, really good reason for needed to whip up your own.

第二

我们不需要包装，你可以简单回报 GenericEntity 。这将自动将元素包装在复数包装元素中，即< product> - > < products> 。

We don't need the wrapper, you can simple return a GenericEntity. This will automatically wrap the elements in a "plural wrapper" element, i.e. <product> -> <products>.

List<Product> list = new ArrayList<>();
GenericEntity<List<String>> entity = new GenericEntity<List<Product>>(list) {};
Response response = Response.ok(entity).build();

要接受资源方法中的正文，只需接受 List< Product> 作为参数就足够了。它将接受< products>< product />< product />< / products>

For accepting a body in resource method, simply accepting List<Product> as an argument is enough. It will accept <products><product/><product/></products>

更新

检索列表< Product> 在客户端，我们应该使用 GenericType 。请这篇文章。

To retrieve the List<Product> on the client side, we should make use of GenericType. Se this post.

Jersey 1

WebResource resource = client.resource("...");
List<Product> products = resource.get(new GenericType<List<Product>>(){});

泽西岛2 / JAX-RS 2

Jersey 2/JAX-RS 2

Response response = ...
List<Product> products = response.readEntity(new GenericType<List<Product>>(){});

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