05 - mvc with struts - mvc with struts.pdf · 1 cse 135 the mvc design pattern & the struts...

1

CSE 135

The MVC Design Pattern &The Struts Framework

for every JSP page pfor every type of request r to p

insert in p code to implement the action requested by r

Previous Attempts:Model 1 Design Pattern

Messy JSP!

Messy JSP!

students.jspIf request to insert student

perform SQL INSERTIf request to delete student

perform SQL UPDATEIf request to update student

perform SQL DELETE

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http://.../students.jsp?action=insert&...

perform SQL DELETE

HTML part of the JSPINSERT STUDENTUPDATE STUDENTDELETE STUDENT

http://.../students.jsp?action=update&...

http://.../students.jsp?action=delete&...

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The MVC Design Pattern:Separating Model, View & Controller

View

• Development “Best Practice”

Control unit 2Control unit 1

View

Controller

BrowsableWeb/ multi-device

applications

• Known well before web items– Smalltalk pioneered

• Model: Access to Underlying Databases and Info Sources

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Databases

Model• Controller: Control Flow of Web App

• View: Look-and-Feel

The MVC Design Pattern

• MVC originated as Model 2 in web developers community

• Model 1: Application logic is attached to JSPs– Similar to previous attempts of students.jsp

• Model 2: Data access and control flow decisions in Java Beans

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3

Data Entry Example – MVC Attempt

students.jsp

HTML part of the JSPINSERT STUDENT

View

INSERT STUDENTUPDATE STUDENTDELETE STUDENT

Insert Student

UpdateStudent

Delete Student

Controller/Actions

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DB

Model Java classes export methods that encapsulate SQL accessModel

The Process and the Frictions

Analysis/S ifi i

Business Process Owner (Client)

COMMUNICATIONbusiness process T get of Ph e 1Specification

Phase

DevelopmentPhase

Chief Architect/Technical Project Leader

business process and specification of Web application

COMMUNICATION technical specification

Target of Phase 1

Target of Phase 3

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Phase pand development

Developer

Problem is even worse in evolution phase when application logic is hidden in thousands of lines of code

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Struts

• Black-Box Framework Implementing MVC– Framework: reusable “partial” application

St t id hi h l l t l • Struts ActionServlet provides high level control of workflow (i.e., “what happens next”)

• You provide Beans and files to customize framework according to your application needs1. JSPs provide HTML presentation (View)2. ActionForm Beans “collect” form data (Part of Controller)

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3. Action Beans provide details of flow (Part of Controller)4. struts-config.xml declares Beans and JSPs

How To Develop Struts Applications

From 10 Miles High:• Pass high-level control to ActionServlet

– By appropriate URL mapping in web.xml

• Design “workflow” in diagrams and then code it in struts-config.xml

• Develop ActionForm Beans responsible for collecting data

• Develop Action Beans responsible for changing

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p p g gthe state of the application and deciding next step

• Develop Model Beans (not part of Struts) responsible for encapsulating database access

• Develop HTML and JSP pages for user interface

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ViewView

Struts application lifetime: How is a browser request processed?

ActionForward(Page or Action)

Request/SessionScopeRequest/SessionScope

DataDataget

ActionFormActionForm

HTTP Request ModelBean

ActionServlet

ActionAction2

3

567

HTTP Response

InitiatingPage

4Form Validation

set

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ModelModel

ControllerController

struts‐config.xml

DB

1Error

Struts Single Request Processing (cont’d)

• When web app is loaded, ActionServlet parses struts-config.xml and associates URL paths with A ti and A ti F Beans

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with Action and ActionForm Beans– Location of struts-config.xml is given in web.xml

• The user issues an HTTP request from an initiating page P to the ActionServlet

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10

6


• The ActionServlet instantiates the ActionFormBean associated with the HTTP request URL in t t fi l and sets its properties

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struts-config.xml, and sets its properties using the HTTP request parameters (user-submitted data)

• The ActionForm Bean validates its property values and if validation fails, ActionServletresponds with the initiating page P displaying appropriate error messages for the user to

4

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appropriate error messages for the user to correct his/her form data


• If validation succeeds, the ActionServletinstantiates the Action Bean associated with the HTTP request URL in t t fi l and

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HTTP request URL in struts-config.xml, and calls its execute method passing as parameters the ActionForm Bean, the HTTP request and the HTTP response objects

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• Within its execute method, the Action Bean instantiates/calls Model Beans, which open a connection to the database execute SQL

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connection to the database, execute SQL operations, and return sets of tuplesThe Action Bean places the sets of tuples in the session so that JSP pages (View components) can access them

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• The Action Bean returns to the ActionServletone of the ActionForwards with which the HTTP request URL is associated in t t fi l

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request URL is associated in struts-config.xmlAn ActionForward is a possible outcome of the Action Bean and represents either an JSP/HTML page or another Action that will be the response to the user’s requestUpon receiving the ActionForward, the

d t th ’ t

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ActionServlet responds to the user’s request with the corresponding JSP/HTML page or Action

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Install Struts

• We will use Struts 1.3 for Phase 2 of the project– Struts 2 will be covered later on and will not be used

for the projectfor the project• Download struts-1.3.10-all.zip• Struts is only a package containing:

\doc, \src, \lib, \apps• Within \apps is a set of *.war files

– struts-blank-1.3.10.war

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– struts-examples-1.3.10.war– struts-cookbook-1.3.10.war

Struts Examples

• To play with Struts examples:– Copy struts-cookbook-1.3.10.war under \webapps

A htt //l lh t 8080/ t t kb k 1 3 10/– Access http://localhost:8080/struts-cookbook-1.3.10/• To play with more Struts examples:

– Copy struts-examples-1.3.10.war under \webapps– This automatically deploys a new web app directory– Access http://localhost:8080/struts-examples-1.3.10/

• To start your own Struts application:

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– Copy struts-blank-1.3.10.war under \webapps– Rename \struts-blank-1.3.10 to \your_app_name

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Pass Control to ActionServlet

web.xmll

URLs of requests ending with “.do”, pass all .do requests to ActionServlet

<servlet>

<servlet-name>action</servlet-name>

<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>

<init-param>

<param-name>config</param-name>

<param-value>/WEB-INF/struts-config.xml</param-value>

</init-param>

l d 2 /l d

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<load-on-startup>2</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>action</servlet-name>

<url-pattern>*.do</url-pattern>

</servlet-mapping>

Let’s reconsider the “students” example

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10

Data Entry Example - 7th Attempt

Web Application Workflow

Students(hyperlink)

menu.jsp

success

success !validate

!validate

students.jspshowStudents.doshowStudents.do

insertStudent.doinsertStudent.do

StudentFormInsertUpdateStudentFormInsertUpdate

StudentFormInsertUpdateStudentFormInsertUpdate StudentForm

DeleteStudentForm

Delete

Insert(button)

Update(button)

Delete(button)

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success

success

updateStudent.doupdateStudent.do

deleteStudent.dodeleteStudent.do

Data Entry Example - 7th Attempt

Web AppliationWorkflow

Students(hyperlink)

menu.jsp

set getRequest ScopeRequest Scope

StudentsRowSetStudentsRowSet

success

success !validate

!validate

students.jspshowStudents.doshowStudents.do

insertStudent.doinsertStudent.do


StudentFormInsertUpdateStudentFormInsertUpdate StudentForm

DeleteStudentForm

Delete

Insert(button)

Update(button)

Delete(button)

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success

success

updateStudent.doupdateStudent.do

deleteStudent.dodeleteStudent.do

StudentModel.getAllStudents()(SELECT * FROM Students)

StudentModel.insertStudent()(INSERT INTO Students…)

StudentModel.updateStudent()(UPDATE Students…)

StudentModel.deleteStudent()(DELETE FROM Students…)

DB

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ViewView

showStudents.do Request Processing

students.jsp getRequest ScopeRequest Scope

StudentsRowSetStudentsRowSet


…/showStudents.doStudentModelActionServlet ShowStudentsActionShowStudentsAction

success

menu.jsp

set

2

3

5

4

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ModelModelstruts‐config.xml

DB1

showStudents.do Configuration

struts-config.xml<struts-config>

...

<action-mappings>

<action

path="/showStudents"

type="dataentry.actions.ShowStudentsAction">

<forward

name="success”

path "/pages/students jsp"/>

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path="/pages/students.jsp"/>

</action>

...

</action-mappings>

...

</struts-config>

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showStudents.do Action Bean

ShowStudentsAction.javapackage dataentry.actions;

import javax.sql.RowSet;

import org.apache.struts.action.Action;

import org.apache.struts.action.ActionForm;

import org.apache.struts.action.ActionForward;

import dataentry.model.StudentModel;

...

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public class ShowStudentsAction extends Action {

...

showStudents.do Action Bean

ShowStudentsAction.java (cont’d)...

public ActionForward execute(public ActionForward execute(

ActionMapping mapping, ActionForm form,

HttpServletRequest request,

HttpServletResponse response) throws DBException {

// retrieve all students

RowSet crsStudents = StudentModel.getAllStudents();

// t th R S t i th t

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// store the RowSet in the request scope

request.setAttribute("crsStudents", crsStudents);

return mapping.findForward("success");

}

}

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showStudents.do Model Bean

StudentsModel.javapackage dataentry.model;

...

public class StudentModel {

private static String selectStr = ...;

private static String insertStr = ...;

private static String updateStr = ...;

private static String deleteStr = ...;

public static CachedRowSet getAllStudents() { }

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public static CachedRowSet getAllStudents() {...}

public static void insertStudent(StudentBean student) {...}

public static void updateStudent(StudentBean student) {...}

public static void deleteStudent(StudentBean student) {...}

}

showStudents.do ActionForward

students.jsp<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>

...

<%-- -------- Iteration Code -------- --%>

<% RowSet crsStudents = (RowSet) request.getAttribute("crsStudents");

while (crsStudents.next()) { %>

<tr>

...

<td>

<html:text property=”middle" size="15"

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p p y

value="<%=crsStudents.getString(\”middleName\")%>" />

</td>

...

</tr>

<% } %>

...

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ViewView

insertStudent.do Request Processing

showStudents.do(Step on Slide 8)2


…/insertStudent.do StudentModel

ActionServlet

InsertStudentActionInsertStudentAction

success

students.jsp

Form ValidationError

2 5 6

7

4

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ModelModel


struts‐config.xml

DB

rror

1 34

insertStudent.do Configuration

struts-config.xml...

<form bean name="studentFormInsertUpdate”<form-bean name="studentFormInsertUpdate”

type="dataentry.forms.StudentFormInsertUpdate"/>

...

<action

path="/insertStudent”

type="dataentry.actions.InsertStudentAction"

validate="true”

scope "request"

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scope="request"

input="/showStudents.do”

name="studentFormInsertUpdate">

<forward name="success" path="/showStudents.do”

redirect="true"/>

</action>

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insertStudent.do ActionForm Bean

StudentFormInsertUpdate.java

package dataentry forms;package dataentry.forms;

...

public class StudentFormInsertUpdate extends ActionForm {

private String id = null;

private String first = null;

private String middle = null;

i t St i l t ll

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private String last = null;

public String getId() { return id; }

public void setId(String id) { this.id = id; }

...


StudentFormInsertUpdate.java (cont’d)

...

/**

* Reset all properties to their default values.

*/

public void reset(ActionMapping mapping,

HttpServletRequest request) {

setId(null);

tFi t( ll)

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setFirst(null);

setMiddle(null);

setLast(null);

}

...

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StudentFormInsertUpdate.java (cont’d)...

public ActionErrors validate(ActionMapping mappingpublic ActionErrors validate(ActionMapping mapping,

HttpServletRequest request) {

ActionErrors errors = new ActionErrors();

if ((id == null) || (id.length() < 1))

errors.add("idMsgTag1",

new ActionMessage("errors required" ”ID"))

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new ActionMessage("errors.required", ”ID"));

...

return errors;

}

}

insertStudent.do Action Bean

InsertStudentAction.javapublic class InsertStudentAction extends Action {

public ActionForward execute(ActionMapping mappingpublic ActionForward execute(ActionMapping mapping,

ActionForm form, HttpServletRequest request,


// cast the form

StudentFormInsertUpdate iForm =

(StudentFormInsertUpdate) form;

// i t th t d t

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// insert the student

StudentModel.insertStudent(iForm);

return mapping.findForward("success");

}

}

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insertStudent.do ActionForward

students.jsp<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>

...The corresponding A i F b

<html:errors />

...

<tr>

<html:form action="/insertStudent">

<td><html:text property="id" size="10" /></td>

<td><html:text property="first" size="15" /></td>

<td><html:text property="middle" size="15" /></td>

ActionForm bean will also be used to populate HTML

form

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<td><html:text property middle size 15 /></td>

<td><html:text property="last" size="15" /></td>

<td><html:submit value="Insert" /></td>

<td><html:reset /></td>

</html:form>

</tr>

...

struts-config.xml Structure

<struts-config><form-beans>...</form-beans>

<global-exceptions>...</global-exceptions>

<global-forwards>...</global-forwards>

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<action-mappings>...</action-mappings>

<message-resources parameter="MessageResources" />

</struts-config>

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Global Exceptions

struts-config.xml

<! ==================== Global Exception Definitions >

<global-exceptions>

<exception key="error.db"

type="dataentry.db.DBException"

path="/pages/dbException.jsp"/>

</global-exceptions>

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Global Exceptions

DBException.java

package dataentry db;package dataentry.db;

public class DBException extends Exception {

public DBException() {

super();

}

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public DBException(String message) {

super(message);

}

}

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Global Exceptions

StudentModel.java

public static void insertStudent(public static void insertStudent(

StudentFormInsertUpdate student) throws DBException {

try {

...

} catch (SQLException ex) {

throw new DBException(ex);

} catch (NamingException ex) {

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} catch (NamingException ex) {

throw new DBException(ex);

}

}

Global Exceptions

InsertStudentAction.java

public class InsertStudentAction extends Action {public class InsertStudentAction extends Action {

public ActionForward execute(ActionMapping mapping,

ActionForm form, HttpServletRequest request,


...

StudentModel.insertStudent(...);

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...

}

}

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Global Exceptions

dbException.jsp

<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>

<html>

<body>

<h2>Database Exception</h2>

...

<h3>Here is the message generated by the thrown database

exception:</h3>

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<p><html:errors /></p>

</body>

</html>

Global Forwards

struts-config.xml



<global-forwards>

<forward name="showStudents" path="/showStudents.do"/>

</global-forwards>

menu.jsp

<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>

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<b>Data Entry Menu</b>

<ul>

<li><html:link forward="showStudents">Students</html:link></li>

...

</ul>

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Message Resources

MessageResources.properties

# -- app --

app.title=Struts Data Entry Application

...

students.jsp

<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%>

<html>

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<head>

<title><bean:message key="app.title" /></title>

</head>

...

</html>

05 - mvc with struts - mvc with struts.pdf · 1 cse 135 the mvc design pattern & the struts...

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