The IT Journey: Expose Service Layer via RESTful services in Spring + Unit Test with TDD

Series:

Goal:

· We are going to build on top of Service Layer (that we covered in the previous post.)

· We are going to expose Service Layer as RESTful APIs.

· We are going to use TDD to develop the RESTful service functionality.

· We are going to use Jackson which returns JSON object in the RESTful response.

Steps:

1. add dependencies to pom.xml

a. web, mvc, Jackson, selenium, etc.

2. Amend context.xml to include MVC

3. Amend web.xml to include RESTful/Servlet mapping, etc.

4. Create a POJO which exposes the service layer.

a. Accepts HTTP requests (standard HTTP verbs, POST, PUT, GET, etc.)

b. Invokes service layer

c. Returns response as JSON object.

5. Create a Test class which uses Selenium to fire HTTP request with desired RESTful service with proper Verb (we will demonstrate a GET call.)

6. Run the Test Suite

Step 1: Add dependencies

For Spring MVC + JSON related stuff + Selenium (the exact packages are mentioned below in Appendex.)

Step 2: Amend context.xml

Ensure that all relevant namespace and xsd references are included:

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.1.xsd

http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd

http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd

http://www.springframework.org/schema/oxm http://www.springframework.org/schema/oxm/spring-oxm-4.1.xsd

http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.1.xsd

http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.1.xsd">

Scan the RESTFul web layer package:

<context:component-scan base-package="com.mycos.dpweb.ws" />

Add JSON handler:

</bean>

<!--

maps handler methods based on HTTP paths

-->

<util:list id="beanList">

</util:list>

</property>

</bean>

<!--

Converts JSON to POJO and vice versa

-->

</bean>

Step 3: Amend web.xml

<context-param>

<param-name>contextConfigLocation</param-name>

<param-value>/WEB-INF/classes/context.xml</param-value>

</context-param>

<!-- Loads the Spring web application context using the config file defined

above. -->

<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

</listener>

<!-- Define the Spring Dispatcher Servlet for the REST services. The 'contextConfiguration'

param with an empty value means that the Spring Context won't try to load

a default file called restservices-servlet.xml -->

<servlet-name>restservices</servlet-name>

<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>

<init-param>

<param-name>contextConfigLocation</param-name>

<param-value></param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

<!-- This Servlet mapping means that this Servlet will handle all incoming

requests -->

<servlet-mapping>

<servlet-name>restservices</servlet-name>

<url-pattern>/ws/*</url-pattern>

</servlet-mapping>

Step 4: Create POJO for RESTFul service

1. Create a package and a Java class

2. Annotate with @Controller

3. Inject Service Layer Object

4. Inject “View”

5. Inject @RequestMapping wherever is needed.

Please note that for simplicity I have eliminated the detail steps to get to the code. But essentially you start with a blank template method, implement unit test cases, and then start adding flesh to the template.

Code:

@Controller

public class XxxConroller {

@Autowired

private XxxService xxxService;

@Autowired

private View jsonView_i;

@RequestMapping(value = "/user/{userId}", method = RequestMethod.GET)

public ModelAndView getUserID(@PathVariable("userId") String userId) {

/* validate user Id parameter */

if (isEmpty(userId)) {

String sMessage = "Error invoking getUserById - Invalid user Id parameter";

return createErrorResponse(sMessage);

}

try {

return new ModelAndView(jsonView_i, DATA_FIELD, this.xxxService.getUser(userId));

} catch (Exception e) {

String sMessage = "Error invoking getAllLocations. [%1$s]";

return createErrorResponse(String.format(sMessage, e.toString()));

}

Step 5: Create Test Class.

1. Create a package and a class.

public class XxxRESTAPITest extends XxxDBUnitTest{ //extend for the DBUnitTest classes created in the previous post

Create a properties file with expected value. Test case is going to use this value to compare with the json object returned by the RESTful API call. ( ClassPathResource locationTblContent = new ClassPathResource("/webtest/webtest.properties");

2. Handle JSON object.

· You can store the entire json object (john_expected_data={"data"\:{"userId"\:"john","isxxx"\:"Y"}})

· You can store only the relevant value and parse the JSON object from the invoked RESTful call to assert a success or unsuccessful call.

@Test

public void testgetUserByIDRESTAPI() throws Exception {

init();

this.testHTML("user/john/", this.prop.getProperty("john_expected_data"));

}

StringBuilder strBldr = new StringBuilder();

strBldr.append(prop.get("url"));

strBldr.append(uri);

WebDriver driver = new FirefoxDriver();

driver.get(strBldr.toString());

log.debug(driver.findElement(By.tagName("body")).getText());

assertEquals(expectedValue, driver.findElement(By.tagName("body")).getText());

driver.close();

driver.quit();