Struts 2 + Spring

Struts 2 + Spring Aug 19th, 2009 Bryan Hsueh

Agenda

Layer architecture: Presentation, Business Logic, DB

Spring framework

Model-View-Controller

Struts 2

Case A: Simple POJO

Case B: Decouple web layer (Action) from Service

Case C: Use Service and DTO

Integration between layers

Other thoughts

Layer Architecture

Client :

Presentation

Application Server :

Business Logic

Database :

Data Modeling

Spring Modules Core Struts or Spring MVC Context Web AOP JMS JCA DAO ORM (Hibernate) JMX … … DB browser

Model-View-Controller Controller Model DB Business Service Object Front Controller Servlet Controller View JSP Browser Server API getXyz()

Model-View-Controller

Provide a loose coupling between View and Model, which can make application significantly easier to create and maintain.

View:

Presentation: JSP, Tablib, Tiles, Validation, etc.

Controller:

application flow is mediated by a central/front controller

front controller delegates requests to a handler/controller/action

each handler acts as an adapter between the request and the Model

control is usually then forwarded to appropriate View

Model:

represents, or encapsulates, an application's business logic or state

provide business APIs to be used by upper layers

Struts 2 DB * One way of interpreting Struts 2 MVC. Why put Action in Model?

A Simple POJO (case A)

public String add () {

....

return “success”;

}

public String update () {

....

return “success”;

}

public String login () {

....

if (ok) return “success”;

else return “error”;

}

}

public class User { private String name; private String gender; private Date birth; public String getName() { return name; } void setName(String s) { name = s; } public Date getBirth() { ... } void setBirth(Date d) { ... } public String getGender() { ... } void setGender(String s) { ... } Could use simple POJO as Action in Struts 2

In struts.xml <action name=“user_add" class=" xxx.User " method=" add "> <result>/jsp/user.jsp</result> <result name=“error”>/jsp/error.jsp</result> </action> <action name=“user_delete" class=" xxx.User " method=“ update "> <result>/jsp/user.jsp</result> </action> <action name=“user_login" class=" xxx.User " method=“ login "> <result name=“ success ”>/jsp/user.jsp</result> <result name=“ error ”>error.jsp</result> </action> <action name=“user_ * " class=" xxx.User " method=“ {1} "> <result>/jsp/user.jsp</result> <result name=“error”>/jsp/error.jsp</result> </action>

The Action in Struts 2

The Action class actually plays more role as Controller.

Handle the interaction between View and Model

Use the data and APIs from Model (business service)

Heavily coupled with the view page (navigation logic)

(new in Struts 2) Can also add properties, to be used by View.

Combine ActionForm (in Struts 1) in the Action

(new in Struts 2) Could use POJO (model) as Action

Works with simple object. But …

Heavy coupling of navigation logic in each function

Forward to different view: also in action mapping (struts.xml)

Not easy to manage the coupling between layers

Business layer should not tie to the web layer framework.

In most cases, Action will extend from ActionSupport class

ActionSupport class (case B) public class UserAction extends ActionSupport { private User user; private String name; private String gender; private Date birth; public String getName() { return name; } void setName(String s) { name = s; } public Date getBirth() { ... } void setBirth(Date d) { ... } public String getGender() { ... } void setGender(String s) { ... } public class ActionSupport implements Action , Validateable , ValidationAware , TextProvider , LocaleProvider , Serializable public String add () { user.add(); .... return “success”; } public String update () { user.update(); .... return “success”; } public String login () { user.login(); .... if (ok) return “success”; else return “error”; } } Decouple business service from web layer

In struts.xml <action name=“user_add" class=" xxx.UserAction " method=" add "> <result>/jsp/user.jsp</result> <result name=“ error ”>/jsp/error.jsp</result> </action> <action name=“user_delete" class=" xxx.UserAction " method=“ update "> <result>/jsp/user.jsp</result> </action> <action name=“user_login" class=" xxx.UserAction " method=“ login "> <result name=“ success ”>/jsp/user.jsp</result> <result name=“ error ”>error.jsp</result> </action> <action name=“user_ * " class=" xxx.UserAction " method=“ {1} "> <result>/jsp/user.jsp</result> <result name=“error”>/jsp/error.jsp</result> </action>

Service and DTO (case C) public class UserAction extends ActionSupport { private AccountService accountService; private User user; public AccountService getAccountServic () { return user; } void setAccountServic (AccountService s) { accountService = s; } public User getUser () { return user; } void setUser (User u) { user = u; } public String add () { accountService.add(user); .... return “success”; } public String update () { accountService.update(user); .... return “success”; } public String login () { accountService.login(user); .... if (ok) return “success”; else return “error”; } } Use Business Service and DTO (Data Transfer Object)

Service and DTO

public class AccountService {

public String add(User u) {

....

}

public String update(User u) {

....

}

public String login(User u) {

....

}

}

public class User { private String name; private String gender; private Date birth; public String getName() { return name; } void setName(String s) { name = s; } public Date getBirth() { ... } void setBirth(Date d) { ... } public String getGender() { ... } void setGender(String s) { ... } } DTO: simple Java bean, reduce overhead Business Service Object: - implement business logic and provide service API to upper layers - managed by container - usually fewer service objects than DTOs - use Data Access Object (DAO) to get data (DTO) from DB

Web and Business Layers DB Business Service Object Web Service, XML-RPC, etc. * Business layer should not tie to web layer framework. Spring MVC Struts

Integration between layers