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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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

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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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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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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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@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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@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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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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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")
@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")
@GET @Path("/result")
public ThymeleafViewable result(…) {
Map<String, Object> models = …
"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);
"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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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;
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 {
@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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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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Java EE Action-Based MVC with Thymeleaf

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