一. 背景知识
有时候微服务需要提供给多个消费者, 而不通过的消费者可能希望依据自身情况使用不同的协议. 另一方面, 有时候如果原本服务以 dubbo 协议提供服务, 但是为了调试或者监控方便, 我们也提供 rest 协议.
本文示例服务者同时提供 dubbo 和 rest 协议. 使用的 dubbo 版本为 2.7.1, springboot 版本为 2.1.5.
为了真实地模拟不同微服务之间的调用, 本文将服务者和消费分开. 对应的项目有两个, 分别为dubboshop-inventory(服务者)和dubboshop-order(消费者). 其结构如下:
dubboshop-inventory (库存微服务. 这个项目主要演示服务提供者角色)
|- dubbo-api: 包含服务接口和 DTO 对象. 打包成 `dubboshop-inventory:1.0.0-snapshot.jar`, 通过 `mvn install`到本地或者`mvn deploy`部署到私服, 在下面`dubboshop-order`项目中引用依赖.
|- fun.faceless.dubboshop.comms.entity.Result.java
|- fun.faceless.dubboshop.comms.entity.CommRetCode.java
|- dubbo-provider: 服务接口具体实现类
|- fun.faceless.dubboshop.inventory.dubboprovider.DubboApplication.java
|- fun.faceless.dubboshop.inventory.dubboprovider.impl.InventoryProviderImpl.java
dubboshop-order (订单微服务)
|- dubbo-provider: 订单服务的提供者, 同时是dubboshop-inventory服务的消费者. 这里主要演示其作为消费者的角色.
|- fun.faceless.dubboshop.order.dubboprovider.impl.OrderProviderImpl.java
二. 通用dubbo配置
本文两个项目都作为服务者, 也都支持dubbo和rest协议, 所以两者dubbo相关的依赖都包含以下几部分.
1) 首先引入通用 dubbo 依赖
org.apache.dubbo
dubbo-bom
pom
org.apache.dubbo
dubbo
${dubbo.version}
org.apache.thrift
libthrift
org.apache.dubbo
dubbo-spring-boot-starter
org.apache.dubbo
dubbo-dependencies-zookeeper
2.7.1
pom
log4j
log4j
slf4j-log4j12
org.slf4j
2) dubbo rest 依赖
org.apache.dubbo
dubbo-rpc-rest
org.apache.tomcat.embed
tomcat-embed-core
三. 服务者(Provider)实现
3.1 服务接口定义 dubbo-api
1) 数据传输对象定义 Result.java:
注意一定要定义默认构造函数和实现Serializable接口.
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Result implements Serializable {
private static final long serialVersionUID = 1L;
public static String SUCCESS_MSG = "SUCC";
public static String DEFAULT_FAIL_MSG = "FAIL";
private String code;
private String msg;
private String subCode;
private String subMsg;
private String sign;
private Object data;
private Result(String code, String msg, Object data) {
this.code = code;
this.msg = msg;
this.data = data;
this.subCode = "";
this.subMsg = "";
this.sign = "";
}
/**
* Return succ result with given data.
* @return
*/
public static Result succ() {
return new Result(CommRetCode.OK, SUCCESS_MSG, null);
}
/**
* Return succ result with given data.
* @param msg
* @return
*/
public static Result succ(String msg) {
return new Result(CommRetCode.OK, msg, null);
}
/**
* Return failed result with given code, msg, and data
* @param code
* @param msg
* @param data
* @return
*/
public static Result fail(String code, String msg, Object data) {
return new Result(code, msg, data);
}
// 其他省略...
}
2) 通用返回值 CommRetCode.java
package fun.faceless.dubboshop.comms.entity;
public interface CommRetCode {
/** 一切 ok */
public final static String OK = "00000";
// 其他省略...
}
3) 定义服务提供者接口API: InventoryProvider.java
注意 REST 相关的注解都放在接口类中.
package fun.faceless.dubboshop.inventory.dubboprovider;
import javax.ws.rs.*;
import fun.faceless.dubboshop.comms.entity.Result;
import org.apache.dubbo.config.annotation.Service;
import org.apache.dubbo.rpc.protocol.rest.support.ContentType;
/**
* Order Dubbo Service
*/
@Service
@Path("inventory")
@Produces({ContentType.APPLICATION_JSON_UTF_8})
@Consumes({ContentType.APPLICATION_JSON_UTF_8})
public interface InventoryProvider {
@GET
@Path("hello")
Result hello();
/**
* 减扣商品库存
*/
@POST
@Path("debit")
Result debit(@QueryParam("goodsId") int goodsId, @QueryParam("amount") int amount);
}
3.2 服务实现具体实现
本节示例 Inventory 微服务即库存服务提供者.
1) 提供的服务的具体实现类 InventoryProviderImpl.java
package fun.faceless.dubboshop.inventory.dubboprovider.impl;
import fun.faceless.dubboshop.comms.entity.Result;
import fun.faceless.dubboshop.inventory.dao.InventoryDao;
import fun.faceless.dubboshop.inventory.dubboprovider.InventoryProvider;
import lombok.extern.slf4j.Slf4j;
import org.apache.dubbo.config.annotation.Service;
import org.springframework.beans.factory.annotation.Autowired;
@Slf4j
@Service
public class InventoryProviderImpl implements InventoryProvider {
@Autowired
InventoryDao inventoryDao;
@Override
public Result hello() {
return Result.succ("hello from inventory center");
}
@Override
public Result debit(int goodsId, int amount) {
log.debug("debit() goodsId: {}", goodsId);
log.debug("debit() amount: {}", amount);
inventoryDao.debit(goodsId, amount);
return Result.succ();
}
}
2) 服务启动类 DubboApplication.java
package fun.faceless.dubboshop.inventory.dubboprovider;
import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@EnableDubbo
@ComponentScan("fun.faceless.dubboshop.inventory")
@MapperScan("fun.faceless.dubboshop.inventory.dao.mapper")
public class DubboApplication {
public static void main(String[] args) {
SpringApplication.run(DubboApplication.class, args);
}
}
3) 模块配置文件 application-dev.yaml.
多协议支持的配置主要包含:
dubbo.config.multiple = true: 开启多个 protocol 配置绑定.
dubbo.protocols: 支持的 prottocols 列表.
# 此处省略项目其他配置...
# ========= Dubbo Provider ==============
dubbo:
config:
# 开启多个protocol配置绑定
multiple: true
# 注册中心配置
registry:
id: dubboshop-registry
address: zookeeper://yyadmin:2181
group: dubboshop
simplified: true
application:
name: dubboshop-inventory
id: dubboshop-inventory
logger: slf4j
qos-enable: false
qos-accept-foreign-ip: true
qos-port: 22223
protocols:
dubbo:
name: dubbo
port: 20882
server: netty4
rest:
name: rest
server: tomcat
port: 8082
scan:
# dubbo 服务提供者实现类所在包
base-packages: fun.faceless.dubboshop.inventory.dubboprovider
四. 消费者(Consumer)实现
本节示例 Order 微服务即作为订单的模块的服务者, 同时作为上面库存(Inventory)的消费者. 本例注重消费者.
1) 在pom.xml中添加服务者api的依赖:
fun.faceless.dubboshop.inventory
dubboapi
2) 在 OderProviderImpl.java 中消费接口.
package fun.faceless.dubboshop.order.dubboprovider.impl;
public class OrderProviderImpl implements OrderProvider {
@Autowired
private OrderDao orderDao;
// 通过 protocol="dubbo" 或者 protocol="rest" 指定使用的协议
@Reference(protocol="dubbo")
private InventoryProvider inventoryProvider;
@Override
public int createOrder(int userId, int goodsId, int orderCount) {
// 调用服务接口
Result debitResult = inventoryProvider.debit(goodsId, orderCount);
return this.saveOrder(userId, goodsId, orderCount);
}
// 省略其他代码...
}
五. 注意事项
5.1 返回值对象一定要有 默认构造函数 并实现 Serializiable 接口.
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Result implements Serializable {
private static final long serialVersionUID = 1L;
// ...
如果没有默认构造函数, 则在使用 rest protocol 时, 返回值无法消费端反序列化. 消费端会报类似如下异常:
org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class fun.faceless.xxx.Result]: can not instantiate from JSON object (need to add/enable type information?)
如果没有实现 Serializiable 接口, 则在使用 dubbo protocol 时, 服务提供者无法正常序列化返回值. 服务 (provider) 端会报类似如下异常:
Caused by: org.apache.dubbo.remoting.RemotingException: Failed to send response: Response [id=2, version=2.0.2, status=20, event=false, error=null, result=RpcResult [result=Result(code=00000, msg=SUCC, subCode=, subMsg=, sign=, data=null), exception=null]], cause: java.lang.IllegalStateException: Serialized class fun.faceless.dubboshop.comms.entity.Result must implement java.io.Serializable
java.lang.IllegalStateException: Serialized class fun.faceless.dubboshop.comms.entity.Result must implement java.io.Serializable
5.2 调试时修改依赖模块的代码, 注意及时install/deploy
如果修改公共项目, 或者服务提供者接口所在的module, 在 mvn install 或 mvn deploy 之后, 一定也要记得再调用这些 module 的项目重新导入依赖, 否则会因为缓存, 即便重启消费者服务, 也无济于事.
5.3 REST 注解放到服务接口上
对于 rest protocol, 如果是将接口单独打包 (即不带实现类在包内) 提供给消费者. 那么需要将 JAX-RS 相关的注解放到接口上. 否则会报如下错误:
RESTEASY004600: You must use at least one, but no more than one http method annotation on XXX
这是因为 resteasy jax-rs 2客户端似乎不直接接受实现类。要使其工作，必须创建一个正确注释的接口。示例接口注解:
// InventoryProvider.java, 在 `dubboshop-inventory`项目`dubbo-api`模块中, 单独发布给消费者使用.
@Service
@Path("inventory")
@Produces({ContentType.APPLICATION_JSON_UTF_8})
@Consumes({ContentType.APPLICATION_JSON_UTF_8})
public interface InventoryProvider {
@GET
@Path("hello")
Result hello();
/**
* 减扣商品库存
*/
@POST
@Path("debit")
Result debit(@QueryParam("goodsId") int goodsId, @QueryParam("amount") int amount);
}
对应的实现类如下:
// InventoryProviderImpl.java, 在 `dubboshop-inventory`项目`dubbo-provider`模块中, 与消费者无关.
@Slf4j
@Service
public class InventoryProviderImpl implements InventoryProvider {
@Autowired
InventoryDao inventoryDao;
@Override
public Result hello() {
return Result.succ("hello from inventory center");
}
@Override
public Result debit(int goodsId, int amount) {
inventoryDao.debit(goodsId, amount);
return Result.succ();
}
}
5.4 消费端可以指定服务的服务方式
@Reference(protocol="dubbo")
// 或 @Reference(protocol="rest")
private InventoryProvider inventoryProvider;