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What we will do:

  • Session vs Model vs Request.
  • Be cautious about what you use Session for.
  • @SessionAttributes("name") and how it works?
  • Why use Model? "adding elements directly to the HttpServletRequest (as request attributes) would seem to serve the same purpose. The reason to do this is obvious when taking a look at one of the requirements we have set for the MVC framework: It should be as view-agnostic as possible, which means we’d like to be able to incorporate view technologies not bound to the HttpServletRequest as well." - Rod Johnson et. al’s book Professional Java Development with the Spring Framework
  • Spring documentation states that the @SessionAttributes annotation “list the names of model attributes which should be transparently stored in the session or some conversational storage.”

Files List

/pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.in28minutes</groupId>
	<artifactId>in28Minutes-springmvc</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>

	<dependencies>
		<dependency>
			<groupId>javax</groupId>
			<artifactId>javaee-web-api</artifactId>
			<version>6.0</version>
			<scope>provided</scope>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>4.2.2.RELEASE</version>
		</dependency>

		<dependency>
			<groupId>log4j</groupId>
			<artifactId>log4j</artifactId>
			<version>1.2.17</version>
		</dependency>
	</dependencies>

	<build>
		<pluginManagement>
			<plugins>
				<plugin>
					<groupId>org.apache.maven.plugins</groupId>
					<artifactId>maven-compiler-plugin</artifactId>
					<version>3.2</version>
					<configuration>
						<verbose>true</verbose>
						<source>1.8</source>
						<target>1.8</target>
						<showWarnings>true</showWarnings>
					</configuration>
				</plugin>
				<plugin>
					<groupId>org.apache.tomcat.maven</groupId>
					<artifactId>tomcat7-maven-plugin</artifactId>
					<version>2.2</version>
					<configuration>
						<path>/</path>
						<contextReloadable>true</contextReloadable>
					</configuration>
				</plugin>
			</plugins>
		</pluginManagement>
	</build>
</project>

/src/main/java/com/in28minutes/login/LoginController.java

package com.in28minutes.login;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.SessionAttributes;

@Controller
@SessionAttributes("name")
public class LoginController {

	@Autowired
	private LoginService loginService;

	@RequestMapping(value = "/login", method = RequestMethod.GET)
	public String showLoginPage() {
		return "login";
	}

	@RequestMapping(value = "/login", method = RequestMethod.POST)
	public String handleUserLogin(ModelMap model, @RequestParam String name,
			@RequestParam String password) {

		if (!loginService.validateUser(name, password)) {
			model.put("errorMessage", "Invalid Credentials");
			return "login";
		}

		model.put("name", name);
		return "welcome";
	}
}

/src/main/java/com/in28minutes/login/LoginService.java

package com.in28minutes.login;

import org.springframework.stereotype.Service;

@Service
public class LoginService {
	public boolean validateUser(String user, String password) {
		return user.equalsIgnoreCase("in28Minutes") && password.equals("dummy");
	}

}

/src/main/java/com/in28minutes/model/Todo.java

package com.in28minutes.model;

import java.util.Date;

public class Todo {
	private int id;
	private String user;
	private String desc;
	private Date targetDate;
	private boolean isDone;

	public Todo(int id, String user, String desc, Date targetDate, boolean isDone) {
		super();
		this.id = id;
		this.user = user;
		this.desc = desc;
		this.targetDate = targetDate;
		this.isDone = isDone;
	}

	public int getId() {
		return id;
	}

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

	public String getUser() {
		return user;
	}

	public void setUser(String user) {
		this.user = user;
	}

	public String getDesc() {
		return desc;
	}

	public void setDesc(String desc) {
		this.desc = desc;
	}

	public Date getTargetDate() {
		return targetDate;
	}

	public void setTargetDate(Date targetDate) {
		this.targetDate = targetDate;
	}

	public boolean isDone() {
		return isDone;
	}

	public void setDone(boolean isDone) {
		this.isDone = isDone;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + id;
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Todo other = (Todo) obj;
		if (id != other.id)
			return false;
		return true;
	}

	@Override
	public String toString() {
		return String.format(
				"Todo [id=%s, user=%s, desc=%s, targetDate=%s, isDone=%s]", id,
				user, desc, targetDate, isDone);
	}

}

/src/main/java/com/in28minutes/todo/service/TodoService.java

package com.in28minutes.todo.service;

import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

import org.springframework.stereotype.Service;

import com.in28minutes.model.Todo;

@Service
public class TodoService {
	private static List<Todo> todos = new ArrayList<Todo>();
	private static int todoCount = 3;

	static {
		todos.add(new Todo(1, "in28Minutes", "Learn Spring MVC", new Date(),
				false));
		todos.add(new Todo(2, "in28Minutes", "Learn Struts", new Date(), false));
		todos.add(new Todo(3, "in28Minutes", "Learn Hibernate", new Date(),
				false));
	}

	public List<Todo> retrieveTodos(String user) {
		List<Todo> filteredTodos = new ArrayList<Todo>();
		for (Todo todo : todos) {
			if (todo.getUser().equals(user))
				filteredTodos.add(todo);
		}
		return filteredTodos;
	}

	public void addTodo(String name, String desc, Date targetDate, boolean isDone) {
		todos.add(new Todo(++todoCount, name, desc, targetDate, isDone));
	}

	public void deleteTodo(int id) {
		Iterator<Todo> iterator = todos.iterator();
		while (iterator.hasNext()) {
			Todo todo = iterator.next();
			if (todo.getId() == id) {
				iterator.remove();
			}
		}
	}
}

/src/main/java/com/in28minutes/todo/TodoController.java

package com.in28minutes.todo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.SessionAttributes;

import com.in28minutes.todo.service.TodoService;

@Controller
@SessionAttributes("name")
public class TodoController {

	@Autowired
	private TodoService service;

	@RequestMapping(value = "/list-todos", method = RequestMethod.GET)
	public String showLoginPage(ModelMap model, String name) {
		String user = (String) model.get("name");
		model.addAttribute("todos", service.retrieveTodos(user));
		return "list-todos";
	}
}

/src/main/resources/log4j.properties

log4j.rootLogger=TRACE, Appender1, Appender2
 
log4j.appender.Appender1=org.apache.log4j.ConsoleAppender
log4j.appender.Appender1.layout=org.apache.log4j.PatternLayout
log4j.appender.Appender1.layout.ConversionPattern=%-7p %d [%t] %c %x - %m%n

/src/main/webapp/WEB-INF/todo-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    <context:component-scan base-package="com.in28minutes" />

    <mvc:annotation-driven />
    
    <bean
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix">
            <value>/WEB-INF/views/</value>
        </property>
        <property name="suffix">
            <value>.jsp</value>
        </property>
    </bean>
    
</beans>

/src/main/webapp/WEB-INF/views/list-todos.jsp

<html>
<head>
<title>Todos for ${name}</title>
</head>
<body>
<H1>Your Todos</H1>
 ${todos}
</body>
</html>

/src/main/webapp/WEB-INF/views/login.jsp

<html>
<head>
<title>Yahoo!!</title>
</head>
<body>
    <p><font color="red">${errorMessage}</font></p>
    <form action="/login" method="POST">
        Name : <input name="name" type="text" /> Password : <input name="password" type="password" /> <input type="submit" />
    </form>
</body>
</html>

/src/main/webapp/WEB-INF/views/welcome.jsp

<html>
<head>
<title>Yahoo!!</title>
</head>
<body>
Welcome ${name}. You are now authenticated. <a href="/list-todos">Click here</a> to start maintaining your todo's.
</body>
</html>

/src/main/webapp/WEB-INF/web.xml

<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <display-name>To do List</display-name>

    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/todo-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>