将Google原型缓冲区与Jersey / JAX-RS相结合 [英] Combining Google proto buffers with Jersey/JAX-RS

问题描述

目前我有一个RESTful Web服务，其端点通过Jersey / JAX-RS公开：

Currently I have a RESTful web service with endpoints that are exposed via Jersey/JAX-RS:

@Path("/widgets")
public class WidgetResource {
    @GET
    List<Widget> getAllWidgets() {
        // gets Widgets somehow
    }

    @POST
    Widget save(Widget w) {
        // Save widget and return it
    }
}

我使用Jackson将我的POJO序列化/反序列化为JSON ，我的服务都响应并将我的POJO作为 application / json 发回。

I use Jackson for serializing/deserializing my POJOs into JSON, and my service both responds to and sends back my POJOs as application/json.

我现在正在寻找可能使用Google协议缓冲区（或等效技术）来帮助压缩/优化客户端和服务之间的通信，因为JSON /文本非常笨重/浪费。

I am now looking to possibly use Google protocol buffers (or an equivalent technology) to help compress/optimize the communication between client and service, as JSON/text is pretty bulky/wasteful.

实际上，我有一个由微服务架构组成的大型后端;数十种REST服务相互通信;这就是为什么我希望优化在它们之间来回发送的消息。

In reality, I have a large backend that consists of a "microservice" architecture; dozens of REST services communicating with each other; this is why I'm looking to optimize the the messages sent backk and forth between all of them.

所以我问：是否有可能仍然有Jersey / JAX- RS提供我的服务端点，但要删除Jackson / JSON的东西并用Google协议缓冲区替换它？如果是这样，这段代码可能是什么样的？

So I ask: is it possible to still have Jersey/JAX-RS serve up my service endpoints, but to gut out the Jackson/JSON stuff and replace it with Google protocol buffers? If so, what might this code look like?

推荐答案

JAX-RS使用 MessageBodyReader 和 MessageBodyWriter 序列化/反序列化来自不同的媒体类型。您可以在 JAX-RS实体提供商上阅读更多内容。您可以自己编写protobuf对象的序列化/派生的句柄。然后只需通过发现显式或隐式地向应用程序注册提供者。

JAX-RS uses implementations of MessageBodyReader and MessageBodyWriter to serialize/deserialize to and from differen media types. You can read more at JAX-RS Entity Providers. You can write your own the handle the serializion/derialization of your protobuf objects. Then just register the "provider(s)" with the application, either explicitly or implicitly through discovery.

widgets.proto

widgets.proto

package widget;

option java_package = "protobuf.example";
option java_outer_classname = "WidgetsProtoc";

message Widget {
    required string id = 1;
    required string name = 2;
}

message WidgetList {
    repeated Widget widget = 1;
}

编译完成后，我将留下 WidgetsProtoc 具有静态内部 Widget 和 WidgetList 类的类。

When this is compiled, I will be left with a WidgetsProtoc class with static inner Widget and WidgetList classes.

WidgetResource

WidgetResource

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Response;
import protobuf.example.WidgetsProtoc.Widget;
import protobuf.example.WidgetsProtoc.WidgetList;

@Path("/widgets")
public class WidgetResource {

    @GET
    @Produces("application/protobuf")
    public Response getAllWidgets() {
        Widget widget1 = 
                Widget.newBuilder().setId("1").setName("widget 1").build();
        Widget widget2 = 
                Widget.newBuilder().setId("2").setName("widget 2").build();
        WidgetList list = WidgetList.newBuilder()
                .addWidget(widget1).addWidget(widget2).build();
        return Response.ok(list).build();
    }

    @POST
    @Consumes("application/protobuf")
    public Response postAWidget(Widget widget) {
        StringBuilder builder = new StringBuilder("Saving Widget \n");
        builder.append("ID: ").append(widget.getId()).append("\n");
        builder.append("Name: ").append(widget.getName()).append("\n");
        return Response.created(null).entity(builder.toString()).build();
    }
}

您会注意到<$ c的使用$ c>application / protobuf媒体类型。这不是标准媒体类型，但有工作中的工作。此外， Guava库已将此媒体类型定义为 MediaType.PROTOBUF ，转换为application / protobuf，所以我选择坚持 。

You'll notice the use of the "application/protobuf" media type. This isn't a standard media type, but there is a draft in the working. Also the Guava library has define this media type as MediaType.PROTOBUF, which translates to "application/protobuf", so I chose to stick with that.

MessageBodyReader 和 MessageBodyWriter 所有在一个类中定义。您可以选择单独进行。没有区别。

MessageBodyReader and MessageBodyWriter all defined in one class. You can choose to do it separately. Makes no difference.

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import javax.ws.rs.BadRequestException;
import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import protobuf.example.WidgetsProtoc.Widget;
import protobuf.example.WidgetsProtoc.WidgetList;

@Provider
@Produces("application/protobuf")
@Consumes("application/protobuf")
public class WidgetProtocMessageBodyProvder 
                   implements MessageBodyReader, MessageBodyWriter {

    @Override
    public boolean isReadable(Class type, Type type1, 
            Annotation[] antns, MediaType mt) {
        return Widget.class.isAssignableFrom(type) 
                || WidgetList.class.isAssignableFrom(type);
    }

    @Override
    public Object readFrom(Class type, Type type1, Annotation[] antns, 
            MediaType mt, MultivaluedMap mm, InputStream in) 
            throws IOException, WebApplicationException {
        if (Widget.class.isAssignableFrom(type)) {
            return Widget.parseFrom(in);
        } else if (WidgetList.class.isAssignableFrom(type)) {
            return WidgetList.parseFrom(in);
        } else {
            throw new BadRequestException("Can't Deserailize");
        }
    }

    @Override
    public boolean isWriteable(Class type, Type type1, 
            Annotation[] antns, MediaType mt) {
        return Widget.class.isAssignableFrom(type) 
                || WidgetList.class.isAssignableFrom(type);
    }

    @Override
    public long getSize(Object t, Class type, Type type1, 
            Annotation[] antns, MediaType mt) {  return -1; }

    @Override
    public void writeTo(Object t, Class type, Type type1, 
            Annotation[] antns, MediaType mt, 
            MultivaluedMap mm, OutputStream out) 
            throws IOException, WebApplicationException {
        if (t instanceof Widget) {
            Widget widget = (Widget)t;
            widget.writeTo(out);
        } else if (t instanceof WidgetList) {
            WidgetList list = (WidgetList)t;
            list.writeTo(out);
        }
    }  
}

TestCase （确保提供商已在服务器和客户端注册）

TestCase (Make sure the provider is registered both with the server and client)

@Test
public void testGetIt() {
    // Get all list
    WidgetList list = target.path("widgets")
                            .request().get(WidgetList.class);
    System.out.println("===== Response from GET =====");
    for (Widget widget: list.getWidgetList()) {
        System.out.println("id: " + widget.getId() 
                         + ", name: " + widget.getName());
    }

    // Post one 
    Widget widget = Widget.newBuilder().setId("10")
                          .setName("widget 10").build();
    Response responseFromPost = target.path("widgets").request()
            .post(Entity.entity(widget, "application/protobuf"));
    System.out.println("===== Response from POST =====");
    System.out.println(responseFromPost.readEntity(String.class));
    responseFromPost.close();
}

结果：

===== Response from GET =====
id: 1, name: widget 1
id: 2, name: widget 2
===== Response from POST =====
Saving Widget 
ID: 10
Name: widget 10

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