• Enable to render models in the browser without any implementation to specify view.
• Maps view names to actual views
• Built-in view resolvers:
  • InternalResourceViewResolver
  • XmlViewResolver
  • ...

Allow use to set properties, such as prefix or sufix to the view name to generate the view page

Put JSP files as views under WEB-INF, to hide them from direct access (entered URL). Only controllers will be able to access them.

    @Bean
    public ViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);
        return resolver;
    }

• Accepts a configuration file written in XML with the same DTD as Spring's XML bean factories
• XML file default location is /WEB-INF/views.xml
• Implement Ordered interface to allow for flexible participation in ViewResolver chaining

Some special views could be defined via XmlViewResolver (give it a order value) while all remaining views could be resolved by other view resolver

• Define a bean that return XmlViewResolver as ViewResolver in WebConfig
• Create a views.xml in /WEB-INF/views.xml by default or in resources (path src/main/resources)

   <bean id="home" class="org.springframework.web.servlet.view.RedirectView">
       <property name="url" value="http://www.google.com" />
   </bean>

  • If XmlViewResolver is applied, when HomeController runs, the browser is redirected to Google website
• We can set location for dedicated XML file
• Set order

    @Bean
    public ViewResolver xmlViewResolver() {
        XmlViewResolver resolver = new XmlViewResolver();
        Resource resource = new ClassPathResource("/views.xml"); // src/main/resources/views.xml
        resolver.setLocation(resource);
        resolver.setOrder(1);
        return resolver;
    }

• Delegates to other ViewResolver to resolve a view based on the request file name or Accept header
• Set order for the view resolvers to help work properly.
• View resolver uses request media type to select a suitable view for request.

Dishes out JSON, XML or other formatted data with the same components. For example: we have data of a user list. For each type of request user makes, our application returns corresponding formatted data.

• /users.xml return users list in XML format
• /users.json return users list in JSON format
• /users return users list in HTML format

• Override configureContentNegotiation, set default content is html, supports xml and json only.

• Creates a ContentNegotiationManager and configures it with one or more ContentNegotiationStrategy instances.
• The order in which strategies are configured is fixed

    @Override
    public void configureContentNegotiation
            (ContentNegotiationConfigurer configurer) {
        configurer
                .defaultContentType(MediaType.TEXT_HTML)
                .mediaType("xml", MediaType.APPLICATION_XML)
                .mediaType("json", MediaType.APPLICATION_JSON);
    }

• Define a bean that return ContentNegotiatingViewResolver as ViewResolver in WebConfig

    @Bean
    public ViewResolver contentNegotiatingViewResolver(ContentNegotiationManager manager){
        ContentNegotiatingViewResolver cnViewResolver = new ContentNegotiatingViewResolver();
        cnViewResolver.setContentNegotiationManager(manager);
        return cnViewResolver;
    }

• Add JsonViewResolver

Ref: https://spring.io/blog/2013/05/11/content-negotiation-using-spring-mvc

• Import com.fasterxml.jackson.core library

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.8.7</version>
        </dependency>

• Must do:
  • Open Project Structure, go to Artifacts, add all com.fasterxml.jackson.core:jackson-xxxx libraries to output
  • Build Artifacts

• Define a custom view resolver, ex: JsonViewResolver, that implement ViewResolver

public class JsonViewResolver implements ViewResolver {
    @Override
    public View resolveViewName(String viewName, Locale locale)
            throws Exception {
        MappingJackson2JsonView view = new MappingJackson2JsonView();
        view.setPrettyPrint(true);
        return view;
    }
}

• Add JsonViewResolver bean

    @Bean
    public ViewResolver jsonViewResolver(){
        JsonViewResolver resolver = new JsonViewResolver();
        return resolver;
    }

• Add @XmlRootElement(name="user") before the class model we need to get XML formatted data