QConnector

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h1. Programming Guide - Web Services (RESTful)

This guide describes how to develop the _RESTful_ based web services.

In general, the web services should contains the following layers:

* *Web Services Layer* _(a.k.a controller)_ - this is the only place where the client will talk to

* *Services Layer* - contains the business logic on how to handle the client's request

* *DAO layer* - contains the logic on how to retrieve & persist data

!web_services_layers.png!

h2. Step-By-Step

> Assume that you have setup the [[General Info:Setup Development Environment|Eclipse environment]] 

# launch *Eclipse*

# create a new *Dynamic Web Project*:

** _Dynamic web module version_ should set to _2.4_ or above

** _JDK_ compiler compliance version should set to _5.0_ or above

# and then *configure* the project:

## obtain the [[Programming Guide - Web Services (RESTful)#Project-Dependencies|project dependencies]] and then place it in the <code>WEB-INF/lib</code> folder

## replace the *web.xml* with this attachment:"web.xml"

## create the following folder:

*** <code>src/META-INF/spring</code>

## copy attachment:"applicationContext.xml" to <code>src/META-INF/spring</code> folder

*** edit the following line to put in the *root package* of the project

<pre>

<code class="XML">

<context:component-scan base-package="my.root.package"/>

</code>

</pre>

## copy attachment:"restful-servlet.xml" to <code>src/META-INF/spring</code> folder

*** edit the following line to put in the *package name* which contains all of the *controller* classes

<pre>

<code class="XML">

<context:component-scan base-package="my.package.controller"/>

</code>

</pre>

# after configured the project, let's start coding the following layers:

** *Web Services/Controller* - _see_ [[Programming_Guide_-_Web_Services_(RESTful)#Controller-Layer|Coding Guidelines]]

** *Services* - _see_ [[Programming_Guide_-_Web_Services_(RESTful)#Services-Layer|Coding Guidelines]]

** *DAO* - _optional but it's highly recommended to implement it_

# done

> download this sample project, attachment:sample_restful_project.zip to view all code snippets

h2. Project Dependencies

* com.springsource.org.aopalliance-1.0.0.jar

* jackson-core-asl-1.9.0.jar

* jackson-jaxrs-1.9.0.jar

* jackson-mapper-asl-1.9.0.jar

* jcl-over-slf4j-1.6.1.jar

* org.springframework.aop-3.0.5.RELEASE.jar

* org.springframework.asm-3.0.5.RELEASE.jar

* org.springframework.beans-3.0.5.RELEASE.jar

* org.springframework.context.support-3.0.5.RELEASE.jar

* org.springframework.context-3.0.5.RELEASE.jar

* org.springframework.core-3.0.5.RELEASE.jar

* org.springframework.expression-3.0.5.RELEASE.jar

* org.springframework.jdbc-3.0.5.RELEASE.jar

* org.springframework.transaction-3.0.5.RELEASE.jar

* org.springframework.web.servlet-3.0.5.RELEASE.jar

* org.springframework.web-3.0.5.RELEASE.jar

* slf4j-api-1.6.1.jar

* slf4j-log4j12-1.6.1.jar

* spring-security-config-3.0.5.RELEASE.jar

* spring-security-core-3.0.5.RELEASE.jar

* spring-security-web-3.0.5.RELEASE.jar

These dependencies can be found in:

* [[General Info:SearchBrowse_artifact|Nexus]]

* download attachment:web_inf_lib.zip and extract it to <code>WEB-INF/lib</code> folder

h1. Coding Guidelines

This guidelines will be revised anytime to accommodate requirement changes.

h2. Controller Layer

* the controller class must be *thread safe* as there's only *one instance* will be created to serve all web request

* every controller *must annotated* with <code>@Controller</code> at the class level

<pre>

<code class="JAVA">

@Controller

public class RegistrationController {

  ...

}

</code>

</pre>

* use the <code>@RequestMapping</code> to map the web request to the *handler class* or *handler method*, e.g.:

<pre>

<code class="JAVA">

@Controller

@RequestMapping(value = "/reg-services")

public class RegistrationController {

  @RequestMapping(value = "/shopper", method = RequestMethod.POST)

  @ResponseBody

  public boolean registerMember(@RequestBody MemberRegistrationRequest request) {

		return registrationServices.registerMember(request);

  }

}

</code>

</pre>

** for this example, the following web request will be mapped to the *registerMember* method:

*** *request URL* - http://.../.../reg-services/shopper

*** *request method* - POST

* refer to this "link":http://en.wikipedia.org/wiki/Representational_state_transfer#RESTful_web_services for the guidelines about how to choose the appropriate *HTTP methods* and *request URI*

* every *method handler* should be annotated with <code>@ResposeBody</code> at the method level and return a value _(do not return <code>void</code>)_

<pre>

<code class="JAVA">

@ResponseBody

public boolean registerMember(@RequestBody MemberRegistrationRequest request) {

   return registrationServices.registerMember(request);

}

</code>

</pre>

* if an argument is annotated with <code>@RequestBody</code>, the body of the web request will be automatically parsed.

<pre>

<code class="JAVA">

public boolean registerMember(@RequestBody MemberRegistrationRequest request) {

</code>

</pre>

* to bound the value of a *URI template variable*, just annotate, <code>@PathVariable</code> to the *target argument*

<pre>

<code class="JAVA">

@RequestMapping(value = "/shopper/{shopperRefNo}", method = RequestMethod.GET)	

@ResponseBody

public MemberInfo retrieveMemberInfo(@PathVariable int refNo) {

...

</code>

</pre>

** for this example, the value of the URI template variable, *shopperRefNo* will be bound to the argument, *refNo*.

* use <code>@RequestParam</code> to access the specific *Servlet request paramater*. Parameter values will be converted to the declared argument type.

<pre>

<code class="JAVA">

public String setupForm(@RequestParam("petId") int petId)

</code>

</pre>

** *note:* By default, the parameter is required. To make the parameter as optional, set the *required* attribute to *false*, e.g.:

*** <code>@RequestParam(value="id", required=false)</code>

h2. Services Layer

* the service class is just a *POJO* (plain-old-java-object)

* the service class must be *thread safe* if, and only if it is one of the *field members* of the *controller*

* the service class should contains the *business logics only*. Try to delegate the un-relevant codes to other appropriate layers.