在带有Jersey的REST Web服务中返回JSON时，找不到媒体类型= application/json的MessageBodyWriter [英] MessageBodyWriter not found for media type=application/json when returning JSON in REST web service with Jersey

问题描述

我正在尝试使用Jersey创建一个非常简单的REST服务.这是服务代码

I am trying to create a very simple REST service using Jersey. Here is the service code

@Path("/UserService")
public class UserService {

    @GET
    @Path("/users")
    @Produces(MediaType.APPLICATION_XML)
    public List<User> getUsers() {
        User user = new User(1, "Thomas", "Greene");
        List<User> userList = new ArrayList<User>();
        userList.add(user);
        return userList;
    }
}

当我通过Postman运行它时，它会返回一个XML响应

When I run it through Postman, it returns me a XML response

现在，我想返回一个JSON响应.因此，我将媒体类型更改为application/json:

Now, I want to get a JSON response back. So, I changed the mediatype to application/json:

@Path("/UserService")
public class UserService {

    @GET
    @Path("/users")
    @Produces(MediaType.APPLICATION_JSON)
    public List<User> getUsers(){ 
        User user = new User(1, "Thomas", "Greene");
        List<User> userList = new ArrayList<User>();
        userList.add(user);
        return userList;
   }    
}

它在Tomcat日志中给我以下错误:

It gives me the below error in Tomcat logs:

严重:找不到媒体type = application/json，type = class java.util.ArrayList，genericType = java.util.List的MessageBodyWriter.

SEVERE: MessageBodyWriter not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.List.

有人可以指导我如何获取JSON响应吗?

Can someone please guide me how to get a JSON response back?

推荐答案

要将Jackson 2.x用作JSON提供程序，您需要添加

To use Jackson 2.x as your JSON provider you need to add jersey-media-json-jackson module to your pom.xml file:

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-jackson</artifactId>
    <version>2.22.2</version>
</dependency>

然后注册 在您的 / ResourceConfig 子类.

And then register the JacksonFeature in your Application/ResourceConfig subclass.

有关更多详细信息，请查看Jersey 文档

For more details, have a look at Jersey documentation.

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