Development tips : July 2015

Wednesday, July 8, 2015

Rest & Angular - Spring MVC4

To implement Rest & Angular client in MVC4, you need to :

1- Create the rest controller

@RestController
public class ReleasesReportController {

    @RequestMapping("/releases")
    public List<Release> getReleases(){
        List<Release> releases=new ArrayList<Release>();

        Release release1 =new Release();
        release1.setName("Strong bad");

        Release release2 =new Release();
        release2.setName("Back to the feature");

        Release release3 =new Release();
        release3.setName("Trogdor");

        releases.add(release1);
        releases.add(release2);
        releases.add(release3);

        return releases;

    }
}

2- Add JSON mapping to the WebAppInitializer class

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        WebApplicationContext context = getContext();
        servletContext.addListener(new ContextLoaderListener(context));
        ServletRegistration.Dynamic dispatcher = servletContext.addServlet("DispatcherServlet", new DispatcherServlet(context));
        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("*.html");
        dispatcher.addMapping("*.pdf");
        dispatcher.addMapping("*.json");

    }

3- Bind it to the front end

<html ng-app>

<head>
<title> Hello Releases Tracker</title>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.8/angular.min.js" > </script>
<script type="text/javascript" src="releases.js"></script>
</head>

<body>
    <div ng-controller="Releases">
        I have {{releases.length}} releases !

        <ul class="releases-container">
            <li ng-repeat="release in releases">
            {{release.name}}
            </li>

        </ul>
    </div>

</body>

</html>

4- Create the angular file (releases.js) under src/main/webapp folder

function Releases($scope, $http){

   $http.get('http://localhost:8080/ReleaseTracker/releases.json').
       success(function(data){
       $scope.releases=data;
   });

}

Custom validation example - Spring MVC 4

To build a custom validation example you need to:

1-Create an Interface
2-Create a class that implements ConstraintValidator
3-Use the custom validation in the Bean

Step 1:

@Documented
@Constraint(validatedBy=PhoneConstraintValidator.class)
@Target({ElementType.METHOD,ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface Phone {

    String message() default "{Phone}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

Step 2:

public class PhoneConstraintValidator implements ConstraintValidator<Phone, String> {

    @Override
    public void initialize(Phone phone) {

     }

    @Override
    public boolean isValid(String phoneField, ConstraintValidatorContext cxt) {
        if (phoneField == null){
            return false;
        }
        return phoneField.matches("[0-9()-]*");
    }

}

Step 3:

@NotEmpty @Phone
    private String phoneNumber;

Tuesday, July 7, 2015

Famous Exceptions in Spring MVC 4

java.lang.UnsupportedOperationException: Cannot change HTTP accept header

The DispatcherServlet  looks for a bean with the name localeResolver.

If this isn't detected it will use the default,

which is a AcceptHeaderLocaleResovler.

 @Bean
 public MessageSource messageSource(){
  
  ResourceBundleMessageSource messageSource=new

                ResourceBundleMessageSource();
  messageSource.setBasename("messages");
  return messageSource;
  
 }
 
 @Bean
 public LocaleResolver localeResolver(){
  SessionLocaleResolver resolver =new SessionLocaleResolver();
  resolver.setDefaultLocale(Locale.ENGLISH);
  return resolver;
 }
 
 @Override
 public void addInterceptors(InterceptorRegistry registry)
 {
  LocaleChangeInterceptor changeInterceptor=new

                LocaleChangeInterceptor();
  changeInterceptor.setParamName("language");
  registry.addInterceptor(changeInterceptor);
 }

Monday, July 6, 2015

Spring - MVC4 - web.xml file sample

<web-app id="WebApp_ID" version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

<display-name>Archetype Created Web Application</display-name>

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

   <init-param>
       <param-name>contextConfigLocation</param-name>
       <param-value>com.saifmasadeh.WebConfig</param-value>
   </init-param>

   <init-param>
       <param-name>contextClass</param-name>
       <param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
   </init-param>

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

<servlet-mapping>
   <servlet-name>springDispatcherServlet</servlet-name>
   <url-pattern>*.html</url-pattern>
</servlet-mapping>

</web-app>