Getting start Java EE Action-Based MVC with Thymeleaf

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(C) CASAREAL, Inc. All rights reserved.

Getting Start Java EE Action-Based MVC

With Thymeleaf

Masatoshi Tada (Casareal ,Inc) JJUG CCC 2016 Spring

2016-5-21(Sat)

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About This Session

!Answer Your Question "Java EE is Useful Framework As Next Struts?"

!View is Thymeleaf !!Code on GitHub

! https://github.com/MasatoshiTada/jjug-action-based-mvc

! Sorry, comments are written in Japanese

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https://github.com/MasatoshiTada/jjug-action-based-mvc

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About Me

!Masatoshi Tada !Casareal, Inc!GlassFish User Group Japan !Trainer(Java EE/Spring/Swift) !Twitter：@suke_masa

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Agenda

① What’s "Action-Based MVC"? ② Getting Start MVC 1.0(EE 8) ③ Using Jersey MVC & RESTEasy HTML in

EE 7 ④ Other Java EE Technologies You Should

Know ⑤ Final Conclusions

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①What’s

"Action-Based MVC"?

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What’s Action-Based MVC?

!Web Framework which focuses HTTP request & response

!Most of framework are Action-Based ! Struts, Spring MVC, …

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What’s Action-Based MVC?

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View

View

Controller Model

request

response

Struts developer friendly

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What’s "Component-Based MVC"?

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View Backing Bean Model

GUI(VB, Android…) developer friendly -> Struts developer Un-Friendly

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Web Framework of Java EE

! JSF !Responses HTML !Component-Based

! JAX-RS !Responses JSON/XML !Action-Based

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There’s no Framework which is "Action-Based" and "Responses HTML"

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Java EE Standard Action-Based MVC!!

!Model-View-Controller API (MVC 1.0) ! Java EE 8 (2017 H1) !Based on JAX-RS

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②Getting Start

MVC 1.0

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MVC 1.0

!MVC 1.0 is Specification ! ≒Set of Interfaces, Annotations, and Exceptions

!Reference Implementation is Ozark ! Set of Implementation Classes of above

interfaces

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Main Functions of Struts

!Controller !Validation !Handling Exception !View Technology !Transaction Token

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in MVC 1.0?

!Controller → ⭕

!Validation → ⭕

!Handling Exception → ⭕

!View Technology → ❌

!Transaction Token → ❌

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Why No View Technologies in MVC?

!Non-Goal 1 of MVC specification"Define a new view (template) language and processor."

! Instead, MVC provides integration with many view technologies!

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View Technologies We Can Use in MVC 1.0

!MVC ! JSP, Facelets

!Ozark !Thymeleaf, Mustache, Freemarker,

Handlerbars, Velocity, AsciiDoc, …

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If you want to use other View, Implement ViewEngine interface

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Problems of JSP and Facelets

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! JSP !Mix of Logic and View ! Sometime Occurs XSS

!Facelets !Cannot Use All Features in MVC 1.0 !Bad Compatibility with JavaScript

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Let’s Use Thymeleaf!

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!Pure HTML! ! Isolate View and Logic absolutely! ! Good Compatibility with JavaScript!

! Link Expression is very useful! ! Internationalizing message!

! http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#a-multi-language-welcome

http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#a-multi-language-welcome

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Using Thymeleaf in MVC 1.0

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<dependency> <groupId>org.glassfish.ozark.ext</groupId> <artifactId>ozark-thymeleaf</artifactId> <version>1.0.0-m02</version> <scope>compile</scope> </dependency>

! Just adding dependency like below

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Why No Transaction Token Feature?

! In Expert Group’s Mailing-List, "This is a client side concern" ! https://java.net/projects/mvc-spec/lists/

jsr371-experts/archive/2015-07/message/2 ! Spring MVC has no transaction token

feature, too.

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https://java.net/projects/mvc-spec/lists/jsr371-experts/archive/2015-07/message/2

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How to Avoid Double-Submit-Problem

! See TERASOLUNA Guideline ! http://terasolunaorg.github.io/guideline/

5.1.0.RELEASE/en/ArchitectureInDetail/DoubleSubmitProtection.html

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http://terasolunaorg.github.io/guideline/5.1.0.RELEASE/en/ArchitectureInDetail/DoubleSubmitProtection.html

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Preparation : Enabling JAX-RS

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@ApplicationPath("/api") public class MyApplication extends Application { }

Inherit Application class

Add Annotation

jjug-mvc10/src/main/java/com/example/rest/MyApllication.java

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Basic Controller

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@Path("/employee") public class EmployeeController { @GET @Path("/index") @Controller public String index() { return "employee/index.html"; } } Path of View

(extention is REQUIRED)

Indicate as controller method

Mapping to URL & HTTP method

※Italic is feature of MVC

jjug-mvc10/src/main/java/com/example/rest/controller/EmployeeController.java

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Form Class

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public class EmployeeIdForm { @QueryParam("id") @NotBlank @Pattern(regexp = "[1-9][0-9]*") private String id; // setter/getter }

Mapping to "id" Query Parameter

Constraint of Bean Validation

jjug-mvc10/src/main/java/com/example/rest/form/EmployeeIdForm.java

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Send Object to View

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public class EmployeeController { @Inject private Models models;

@GET @Path("/result") @Controller @ValidateOnExecution(type=ExecutableType.NONE) public String result(…) { models.put("employee", employee); return "employee/result.html"; }

Box of Object (Map + Iterator)

Object referred by View



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Referring Object in View

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<table th:unless="${employee == null}"> <tr th:object="${employee}"> <td th:text="*{empId}">99999</td> <td th:text="*{name}">Taro Yamada</td> <td th:text="*{joinedDate}">2020-01-01</td> <td th:text="*{department.deptId}">99</td> <td th:text="*{department.name}">Admin</td> </tr> </table> WEB-INF/views is view folder

jjug-mvc10/src/main/webapp/WEB-INF/views/employee/result.html

Name put to Models

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Validation

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public class EmployeeController { @Inject private BindingResult br;

@GET @Path("/result") @Controller @ValidateOnExecution(type=ExecutableType.NONE) public String result( @Valid @BeanParam EmployeeIdForm form) { if (br.isFailed()) { models.put("bindingResult", br); return "employee/index.html"; // To input view

Box of Messages

Enable Validation

Error Processing



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Showing Error Messages

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<ul th:if="${bindingResult != null}"> <li th:each="message : ${bindingResult.allMessages}" th:text="${message}"> This is Dummy Message </li> </ul>

Get Messages From BindingResult

jjug-mvc10/src/main/webapp/WEB-INF/views/employee/index.html

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Writing Error Messages

!Write messages in src/main/resources/ValidationMessages.properties

! Specify Key of Message to "message" attribute in Annotation

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Specifying Error Message Key

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public class EmployeeIdForm { @QueryParam("id") @NotBlank(message = "{id.notblank}") @Pattern(regexp = "[1-9][0-9]*", message = "{id.pattern}") private String id; // setter/getter

Key of Message with "{}"

jjug-mvc10/src/main/java/com/example/rest/form/EmployeeIdForm.java

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Caution : MVC has No "Form-Binding" Feature

!@BeanParam is not "Form-Binding" !On error, If You want to leave values in

input-components on view, Write view as Next

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Implementing Form-Binding

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<form action="./result" method="get"> <input type="text" name="id" value="" th:value="${param.id == null} ? '' : ${param.id[0]}"/> <input type="submit" value="search"/> </form>

jjug-mvc10/src/main/webapp/WEB-INF/views/employee/index.html

Maybe Complex with selectbox …

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Handling Exception

! Implement ExceptionMapper interface !When error occurs, ExceptionMapper

catches Exception !You can implement multiple

ExceptionMappers

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ExceptionMapper class

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@Provider public class ExceptionMapper implements javax.ws.rs.ext.ExceptionMapper<Exception> { public Response toResponse( Exception exception) { // Forward to Error View… } }

Don’t Forget @Provider

Catches Exception as Method Argument

Implement ExceptionMapper

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Other Features of MVC

! Security (XSS, CSRF) !File Upload, Download !MvcContext (Easy Specifying URL) !Hybrid Class (HTML and REST)

!More Details, See GUGJ Slides below ! http://www.slideshare.net/masatoshitada7/java-ee-8mvc-10

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http://www.slideshare.net/masatoshitada7/java-ee-8mvc-10

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Conclusions of this chapter

!MVC 1.0 + Thymeleaf covers almost features of Struts!

!Need to implement Transaction Token and Form-Binding By Yourself

!Features of MVC are Simple, Reveraging existing Java EE Features.

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③Using Jersey MVC &

RESTEasy HTML in EE 7

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What framework should we use in Java EE 7?

!MVC 1.0 is Java EE 8 ! Java EE 8 will be released in 2017 H1

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Let’s use Jersey MVC or RESTEasy HTML in EE7!

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What’s Jersey MVC?

!Original Extension of Jersey(JAX-RS RI) ! Similar to MVC 1.0 !GlassFish/Payara inside !WebLogic not inside

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What’s RESTEasy HTML?

!Original Extension of RESTEasy (other implementation of JAX-RS) !RESTEasy is inside WildFly/JBoss,

but RESTEasy HTML is not inside

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Basic Jersey MVC

!Register MvcFeature class to Your Application sub class (ResourceConfig is Convinient)

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@ApplicationPath("/api") public class MyApplication extends ResourceConfig { public MyApplication() { register(MvcFeature.class); property(MvcFeature.TEMPLATE_BASE_PATH, "/WEB-INF/views/"); packages(true, "com.example.rest"); } } jjug-jersey-mvc/src/main/java/com/example/rest/MyApplication.java

※Italic is Jersey MVC’s feature

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Basic Jersey MVC

!Return Viewable in controller methods

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@Path("/employee") public class EmployeeController { @GET @Path("/index") public ThymeleafViewable index(…) { return new ThymeleafViewable( "employee/index.html"); } }

My original class (Viewable’s subclass)

jjug-jersey-mvc/src/main/java/com/example/rest/controller/EmployeeControler.java


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Basic Jersey MVC

!Add value to Viewable constructor’s 2nd parameter

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@Path("/employee") public class EmployeeController { @GET @Path("/result") public ThymeleafViewable result(…) { Map<String, Object> models = … return new ThymeleafViewable( "employee/result.html", models); }

Put objects to Map

jjug-jersey-mvc/src/main/java/com/example/rest/controller/EmployeeControler.java


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How to Use Thymeleaf with Jersey MVC

! Implment TemplateProcessor interface (Provided by Jersey)

!AbstractTemplateProcessor class is useful ! implementation of TemplateProcessor

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ThymeleafTemplateProcessor

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@Provider public class ThymeleafTemplateProcessor extends AbstractTemplateProcessor<String> { private TemplateEngine templateEngine; @Inject public ThymeleafTemplateProcessor( Configuration config, ServletContext servletContext) { super(config, servletContext, "html", "html"); TemplateResolver templateResolver = new ServletContextTemplateResolver(); templateResolver.setPrefix((String) config.getProperty( MvcFeature.TEMPLATE_BASE_PATH)); templateEngine = new TemplateEngine(); templateEngine.setTemplateResolver(templateResolver); } // to next slide jjug-jersey-mvc/src/main/java/com/example/rest

/thymeleaf/ThymeleafTemplateProcessor.java


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ThymeleafTemplateProcessor

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// 続き

@Override public void writeTo(...) { WebContext webContext = new WebContext( request, response, servletContext, request.getLocale()); Map<String, Object> map = (Map) viewable.getModel(); webContext.setVariables(map); templateEngine.process(viewable.getTemplateName(), webContext, response.getWriter()); } }

jjug-jersey-mvc/src/main/java/com/example/rest /thymeleaf/ThymeleafTemplateProcessor.java

Thymeleaf write the response


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Validation in Jersey MVC

!Jersey provides @ErrorTemplate annotation to specify error view, but… !This annotation is feature for handling

exception (not for validation) !MVC 1.0 doesn’t have similar feature, so

migration will be difficult !Cannot use "Validation Group" and "Group

Sequence" (Features of Bean Validation)

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Validate in Controller Methods

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@Inject Validator validator; @GET @Path("/result") public ThymeleafViewable result( @BeanParam EmployeeIdForm form) { Set<ConstraintViolation<EmployeeIdForm>> violations = validator.validate(form); if (!violations.isEmpty()) { Map<String, Object> model = …; model.put("violations", violations); return new ThymeleafViewable( "employee/index.html", model); }

Execute Bean Validation

No @Valid to arguments

Validate

On error, return to input view

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Showing Error Message

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<ul th:if="${violations != null}"> <li th:each="violation : ${violations}" th:text="${violation.message}"> This is Dummy Message </li> </ul>

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About This Method

!Advantage !Pure JAX-RS code !Easy MVC 1.0 migration !Avoid excess framework customization

!Disadvantage ! It takes time and effort

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I Tried a variety of methods, this method is best

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Handling Exception

!ExceptionMapper ! Same to MVC 1.0 sample code

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Redirect

! JAX-RSのコードで書けばOK

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@GET @Path("/redirect") public Response redirect( @Context UriInfo uriInfo) throws Exception { URI location = uriInfo.getBaseUriBuilder() .path(HelloResource.class) .path("redirect2") .build(); return Response.status(Response.Status.FOUND) .location(location).build(); }

UriInfo has variety of method to build URI

Specify URI to Location header

Status code 3xx

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Basic RESTEasy HTML

!Create Application’s sub class !No need to register any specific class

! By JAX-RS "Providers"

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@ApplicationPath("/api") public class MyApplication extends Application { }

jjug-resteasy-html/src/main/java/com/example/rest/MyApplication.java

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Basic RESTEasy HTML

!Return Renderable in controller method

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<<interface>>

Renderable

View class (Forward)

Redirect class (Redirect)

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Using Thymeleaf in RESTEasy HTML

!Create Renderable implementation class

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<<interface>>

Renderable

View Redirect ThymeleafView

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ThymeleafView

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public class ThymeleafView implements Renderable { private String templateName; private Map<String, Object> models; private TemplateEngine templateEngine; public ThymeleafView(String templateName) { this(templateName, new HashMap<>()); } public ThymeleafView(String templateName, Map<String, Object> models) { this.templateName = templateName; this.models = models; } void setTemplateEngine(TemplateEngine templateEngine) { this.templateEngine = templateEngine; }

Implement Renderable

※Italic is RESTEasy HTML feature

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ThymeleafView

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// from previous slide @Override public void render(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException, WebApplicationException { response.setCharacterEncoding("UTF-8"); WebContext webContext = new WebContext( request, response, request.getServletContext(), request.getLocale()); webContext.setVariables(models); templateEngine.process(templateName, webContext, response.getWriter()); } }

Call TemplateEngine#process() in render()


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Creating Interceptor Setting TemplateEngine to ThymeleafView

!Use JAX-RS WriterInterceptor !Create custom annotation with

NameBinding, to specify which controller apply interceptor

!There’re many ways(This is not only way)

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Creating annotation

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@NameBinding @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.METHOD, ElementType.TYPE}) @Documented public @interface ThymeleafController { }

Create annotation with @NameBinding

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Creating WriterInterceptor

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@Provider @ThymeleafController public class ThymeleafWriterInterceptor implements WriterInterceptor { private TemplateEngine templateEngine; @PostConstruct public void init() { TemplateResolver resolver = new ServletContextTemplateResolver(); resolver.setPrefix("/WEB-INF/views/"); templateEngine = new TemplateEngine(); templateEngine.setTemplateResolver(resolver); }

Specify annotation you created

Implement WriterInterceptor

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Creating WriterInterceptor

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@Override public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException { Object entity = context.getEntity(); if (ThymeleafView.class.isAssignableFrom(entity.getClass())) { ThymeleafView thymeleafView = (ThymeleafView) context.getEntity(); thymeleafView.setTemplateEngine(templateEngine); } context.proceed(); } }

Set TemplateEngine before context.proceed()

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Controller

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@GET @Path("result") @ThymeleafController public ThymeleafView result(…) { Map<String, Object> models = …; models.put("employee", employee); return new ThymeleafView( "employee/result.html", models); }

Specify annotation →Applying interceptor

View path and values


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Validation and Handling Exception

! Same as Jersey MVC sample code

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Conclusions of this chapter

! In Java EE 7, Use Jersey MVC or RESTEasy HTML!

!Controller methods, views and handling exceptions are same as MVC 1.0!

!They have no BindingResult, so validate in controller methods!

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④Other Java EE

Technologies You Should Know

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JAX-RS

! Specific features of MVC 1.0/Jersey MVC/RESTEasy HTML are not many

!To achieve what you want to do, and trouble-shooting, knowledge of JAX-RS is very important

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JAX-RS Reference

! JSR-339 JAX-RS 2.0 rev.A !You should learn Processing Pipeline

(Appendix C) !https://jcp.org/en/jsr/detail?id=339

! Jersey Document !RESTEasy Document

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https://jcp.org/en/jsr/detail?id=339

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Others

!Bean Validation !CDI ! JPA

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⑤Final Conclusions

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Final Conclusions

!MVC 1.0 + Thymeleaf covers almost features of Struts!

! In EE 7, Use Jersey MVC or RESTEasy HTML!

!Understanding JAX-RS is very important!

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Caution

! Jersey MVC and RESTEasy HTML are NOT "Java EE 7 standard" !They will be out of range

of server vendors’ support ! In "Java EE 7 standard",

JSF is the ONLY HTML Framework

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Enjoy Java EE!!

!Thank you!

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