带有嵌入式Jetty的Jersey - MessageBodyWriter找不到application/json

Question

我试图用Jersey返回POJO作为JSON，但是我得到以下错误:

然而，当我运行应用程序时，我得到:

SEVERE: MessageBodyWriter not found for media type=application/json, type=class com.uk.jacob.model.Person, genericType=class com.uk.jacob.model.Person.

我有以下Jersey资源

@Path("")
public class TestResponse {
    @GET
    @Path("hello")
    @Produces(MediaType.APPLICATION_JSON)
    public Response paramMethod() {
        CacheControl control = new CacheControl();
        control.setMaxAge(60);
        Person jacob = new Person("Jacob");
        return Response
                .ok(jacob)
                .cacheControl(control)
                .build();
    }
}

使用一个简单的Person POJO

public class Person {
    private String firstName;
    public Person(String firstName){
        this.firstName = firstName;
    }
    public String getFirstName(){
        return firstName;
    }
}

使用以下嵌入的Jetty配置

public static void main(String[] args) {
        ServletContextHandler context = new ServletContextHandler(ServletContextHandler.NO_SESSIONS);
        context.setContextPath("/");
        String webPort = System.getenv("PORT");
        if(webPort == null || webPort.isEmpty()) {
            webPort = "3000";
        }
        Server jettyServer = new Server(Integer.valueOf(webPort));
        jettyServer.setHandler(context);
        ServletHolder jerseyServlet = context.addServlet(ServletContainer.class, "/*");
        jerseyServlet.setInitOrder(0);
        jerseyServlet.setInitParameter("jersey.config.server.provider.packages", "com.uk.jacob.api");
        jerseyServlet.setInitParameter("com.sun.jersey.api.json.POJOMappingFeature", "true");
        try {
            jettyServer.start();
            jettyServer.join();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            jettyServer.destroy();
        }
    }

正如您在上面看到的，我已经启用了POJOMappingFeature

    jerseyServlet.setInitParameter("com.sun.jersey.api.json.POJOMappingFeature", "true");

Answer 1

POJOMappingFeature表示Jersey 1。对于Jersey 2，您应该添加以下依赖项

<dependency>
    <groupId>org.glassfish.jersey.media</groupId>
    <artifactId>jersey-media-json-jackson</artifactId>
    <version>${jersey2.version}</version>
</dependency>

并注册特性

jerseyServlet.setInitParameter(
        "jersey.config.server.provider.classnames",
        "org.glassfish.jersey.jackson.JacksonFeature");