Consumer Driven Contracts using Spring Cloud Contract

Jasvinder S Saggu

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Jul 17, 2021

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1. What is CDC or Consumer Driven Contract?
2. Why do I need this?
3. How to implement?
4. Workshop

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.5.2</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.saggu</groupId>
   <artifactId>service-provider</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>service-provider</name>
   <description>Service-provider</description>
   <properties>
      <java.version>11</java.version>
      <spring-cloud.version>2020.0.3</spring-cloud.version>
      <spring-cloud-contract.version>3.0.1</spring-cloud-contract.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-web</artifactId>
      </dependency>

      <dependency>
         <groupId>org.projectlombok</groupId>
         <artifactId>lombok</artifactId>
         <version>1.18.20</version>
      </dependency>

      <dependency>
         <groupId>io.springfox</groupId>
         <artifactId>springfox-boot-starter</artifactId>
         <version>3.0.0</version>
      </dependency>

      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-contract-verifier</artifactId>
         <scope>test</scope>
      </dependency>

      <dependency>
         <groupId>io.springfox</groupId>
         <artifactId>springfox-swagger-ui</artifactId>
         <version>3.0.0</version>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>

   </dependencies>
   <dependencyManagement>
      <dependencies>
         <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
         </dependency>
      </dependencies>
   </dependencyManagement>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-contract-maven-plugin</artifactId>
            <version>3.0.3</version>
            <extensions>true</extensions>
            <configuration>
               <testFramework>JUNIT5</testFramework>
            </configuration>
         </plugin>

         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>

         <plugin>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-contract-maven-plugin</artifactId>
            <version>${spring-cloud-contract.version}</version>
            <extensions>true</extensions>
            <configuration>
               <baseClassForTests>com.saggu.cdc.CdcBaseClass</baseClassForTests>
            </configuration>
         </plugin>

      </plugins>
   </build>

</project>

OrderController.java

package com.saggu.cdc;

import com.saggu.cdc.OrderService.Order;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import static java.util.Objects.isNull;
import static org.springframework.http.ResponseEntity.notFound;
import static org.springframework.http.ResponseEntity.ok;

@RestController
public class OrderController {

    private final OrderService orderService;

    public OrderController(OrderService orderService) {
        this.orderService = orderService;
    }

    @GetMapping(value = "/orders/{orderId}", produces = "application/json")
    public ResponseEntity<Order> getOrder(@PathVariable("orderId") String orderId) {
        Order order = orderService.getOrder(orderId);
        if (isNull(order)) {
            return notFound().build();
        }
        return ok(order);
    }
}

OrderService.java

package com.saggu.cdc;

import lombok.AllArgsConstructor;
import lombok.Data;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

import static java.util.Objects.isNull;
import static org.springframework.http.ResponseEntity.notFound;
import static org.springframework.http.ResponseEntity.ok;

@Service
public class OrderService {

    static Map<String, Order> orders = Map.of(
            "1", new Order("1", "Sony TV", 500.00, 1),
            "2", new Order("2", "Samsung TV", 480.00, 1),
            "3", new Order("3", "Washing Machine", 1500.0, 1)
    );

    public Order getOrder(String orderId) {
       return orders.get(orderId);
    }

    @Data
    @AllArgsConstructor
    static class Order {
        private String orderId;
        private String itemName;
        private double price;
        private int units;
    }
}

CdcBaseClass.java

package com.saggu.cdc;

import io.restassured.module.mockmvc.RestAssuredMockMvc;
import org.junit.jupiter.api.BeforeEach;
import org.mockito.Mockito;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.mock.mockito.MockBean;

@SpringBootTest(classes = ProviderApplication.class)
public abstract class CdcBaseClass {

    @Autowired
    OrderController orderController;

    @MockBean
    OrderService orderService;

    @BeforeEach
    public void setup() {
        RestAssuredMockMvc.standaloneSetup(orderController);

        Mockito.when(orderService.getOrder("1"))
                .thenReturn(OrderService.orders.get("1"));
    }
}

order_for_client1.groovy

package contracts

import org.springframework.cloud.contract.spec.Contract

Contract.make {

    description "should return order by id=1"

    request {
        url "/orders/1"
        method GET()
    }

    response {
        status OK()
        headers {
            contentType applicationJson()
        }
        body(
                "id": "1",
                "itemName": "Sony TV",
                "price": 500.0,
                "units": 1
        )
    }
}