Jersey - 注入的@Context注释。它是如何工作的？ [英] Jersey - The @Context annotation for injection. How does it work?

问题描述

我正在使用Jersey查看一个很好的 REST教程。
在页面下方，有一个构建的Web资源，名为 TodoResource ，它本身包含两个实例变量

I was looking at a good REST tutorial using Jersey. Down the page, there is a web resource that is built which is entitled TodoResource which itself contains two instance variables

public class TodoResource {
    @Context
    UriInfo uriInfo;

    @Context
    Request request;

    String id;

    public TodoResource(UriInfo uriInfo, Request request, String id) {
        this.uriInfo = uriInfo;
        this.request = request;
        this.id = id;
    }
}

我想知道 UriInfo 和请求实例变量是否已初始化？我知道使用 @Context 注释可以注入信息，但这会发生在什么时候？这会由泽西自动处理吗？

I was wondering exactly how the UriInfo and Request instance variables are initialized? I know that using the @Context annotation allows for information to be injected, but at what point does this happen? Will this be handled automatically by Jersey?

推荐答案

泽西岛不会修改这个类，但它在客户端的每个请求中创建。

调用类构造函数后，将注入上下文字段。$
（你应该尝试访问构造函数中的那些字段，它们将是 null ）

After the class constructor was invoked, the context fields are injected.
(Should you try to access those fields inside the constructor, they will be null)

在你的情况下，该类不需要特定的构造函数，所以只需：

In your case, the class wouldn't need a specific constructor, so just:

public TodoResource () {
    // in most cases the ctor stays empty.
    // don't do much work here, remember: the ctor is invoked at every client request
}

但是用 @POST，@ GET，... 注释的内部方法（代表网络资源）你可以访问上下文字段。

But inside methods (which represent web-resources) annotated with @POST, @GET, ... you would have access to context fields.

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