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What we will do:

  • Basic Exception Handling
  • Exception Handling is a cross cutting concern
  • Do not handle exceptions in Controllers or Services, if you cannot add value to them.
  • Bit of refactoring on the controllers
  • @ControllerAdvice and Controller Specific Exception Handling
  • Handling Errors thrown from Views

Useful Snippets

@ControllerAdvice
@EnableWebMvc
public class ExceptionController {

	private Log logger = LogFactory.getLog(ExceptionController.class);

	@ExceptionHandler(value = Exception.class)
	public String handleError(HttpServletRequest req, Exception exception) {
		logger.error("Request: " + req.getRequestURL() + " raised " + exception);
		return "error";
	}
}

<error-page>
	    <location>/WEB-INF/views/jsp/error.jsp</location>
</error-page>

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>org.springframework.security</groupId>
			<artifactId>spring-security-web</artifactId>
			<version>4.0.1.RELEASE</version>
  		</dependency>

       <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-config</artifactId>
            <version>4.0.1.RELEASE</version>
        </dependency>	

		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>

		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>bootstrap</artifactId>
			<version>3.3.6</version>
		</dependency>
		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>jquery</artifactId>
			<version>1.9.1</version>
		</dependency>

		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>bootstrap-datepicker</artifactId>
			<version>1.0.1</version>
		</dependency>
		
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-validator</artifactId>
			<version>5.0.2.Final</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/common/ExceptionController.java

package com.in28minutes.common;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@ControllerAdvice
@EnableWebMvc
public class ExceptionController {

	private Log logger = LogFactory.getLog(ExceptionController.class);

	@ExceptionHandler(value = Exception.class)
	public String handleError(HttpServletRequest req, Exception exception) {
		logger.error("Request: " + req.getRequestURL() + " raised " + exception);
		return "error";
	}
}

/src/main/java/com/in28minutes/common/LogoutController.java

package com.in28minutes.common;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class LogoutController {

	@RequestMapping(value = "/logout", method = RequestMethod.GET)
	public String logout(HttpServletRequest request,
			HttpServletResponse response) {
		Authentication auth = SecurityContextHolder.getContext()
				.getAuthentication();
		if (auth != null) {
			new SecurityContextLogoutHandler().logout(request, response, auth);
		}
		return "redirect:/";
	}
}

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

package com.in28minutes.model;

import java.util.Date;

import javax.validation.constraints.Size;

public class Todo {
	private int id;

	private String user;

	@Size(min = 10, message = "Enter atleast 10 Characters.")
	private String desc;

	private Date targetDate;
	private boolean isDone;

	public Todo() {
		super();
	}

	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/security/SecurityConfiguration.java

package com.in28minutes.security;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;

@Configuration
@EnableWebSecurity
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {

	@Autowired
	public void configureGlobalSecurity(AuthenticationManagerBuilder auth)
			throws Exception {
		auth.inMemoryAuthentication().withUser("in28Minutes").password("dummy")
				.roles("USER", "ADMIN");
	}

	@Override
	protected void configure(HttpSecurity http) throws Exception {
		http.authorizeRequests().antMatchers("/login").permitAll()
				.antMatchers("/", "/*todo*/**").access("hasRole('USER')").and()
				.formLogin();
	}
}

/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 Todo retrieveTodo(int id) {
		for (Todo todo : todos) {
			if (todo.getId() == id)
				return todo;
		}
		return null;
	}

	public void updateTodo(Todo todo) {
		todos.remove(todo);
		todos.add(todo);
	}

	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 java.text.SimpleDateFormat;
import java.util.Date;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.propertyeditors.CustomDateEditor;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.in28minutes.model.Todo;
import com.in28minutes.todo.service.TodoService;

@Controller
public class TodoController {

	@Autowired
	private TodoService service;

	@InitBinder
	protected void initBinder(WebDataBinder binder) {
		SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
		binder.registerCustomEditor(Date.class, new CustomDateEditor(
				dateFormat, false));
	}

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

	@RequestMapping(value = "/add-todo", method = RequestMethod.GET)
	public String showAddTodoPage(ModelMap model) {
		model.addAttribute("todo", new Todo());
		return "todo";
	}

	@RequestMapping(value = "/add-todo", method = RequestMethod.POST)
	public String addTodo(ModelMap model, @Valid Todo todo, BindingResult result) {

		if (result.hasErrors())
			return "todo";

		service.addTodo(getLoggedInUserName(), todo.getDesc(),
				todo.getTargetDate(), false);
		model.clear();// to prevent request parameter "name" to be passed
		return "redirect:/list-todos";
	}

	private String getLoggedInUserName() {
		Object principal = SecurityContextHolder.getContext()
				.getAuthentication().getPrincipal();

		if (principal instanceof UserDetails)
			return ((UserDetails) principal).getUsername();

		return principal.toString();
	}

	@RequestMapping(value = "/update-todo", method = RequestMethod.GET)
	public String showUpdateTodoPage(ModelMap model, @RequestParam int id) {
		model.addAttribute("todo", service.retrieveTodo(id));
		return "todo";
	}

	@RequestMapping(value = "/update-todo", method = RequestMethod.POST)
	public String updateTodo(ModelMap model, @Valid Todo todo,
			BindingResult result) {
		if (result.hasErrors())
			return "todo";

		todo.setUser(getLoggedInUserName());
		service.updateTodo(todo);

		model.clear();// to prevent request parameter "name" to be passed
		return "redirect:/list-todos";
	}

	@RequestMapping(value = "/delete-todo", method = RequestMethod.GET)
	public String deleteTodo(@RequestParam int id) {
		service.deleteTodo(id);

		return "redirect:/list-todos";
	}

}

/src/main/java/com/in28minutes/welcome/WelcomeController.java

package com.in28minutes.welcome;

import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class WelcomeController {

	@RequestMapping(value = "/", method = RequestMethod.GET)
	public String showWelcomePage(ModelMap model) {
		model.put("name", getLoggedInUserName());
		return "welcome";
	}

	private String getLoggedInUserName() {
		Object principal = SecurityContextHolder.getContext()
				.getAuthentication().getPrincipal();

		if (principal instanceof UserDetails)
			return ((UserDetails) principal).getUsername();

		return principal.toString();
	}

}

/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>
    
    <mvc:resources mapping="/webjars/**" location="/webjars/"/>
    
</beans>

/src/main/webapp/WEB-INF/views/common/footer.jspf


<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
<script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<script
	src="webjars/bootstrap-datepicker/1.0.1/js/bootstrap-datepicker.js"></script>

</body>
</html>

/src/main/webapp/WEB-INF/views/common/header.jspf

<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<html>
<head>
<title>Todos Application</title>
<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
	rel="stylesheet">
</head>

<body>

/src/main/webapp/WEB-INF/views/common/navigation.jspf

<nav role="navigation" class="navbar navbar-default">

	<div class="">
		<a href="http://www.in28minutes.com" class="navbar-brand">in28Minutes</a>
	</div>

	<div class="navbar-collapse">
		<ul class="nav navbar-nav">
			<li class="active"><a href="/">Home</a></li>
			<li><a href="/list-todos">Todos</a></li>
		</ul>
		<ul class="nav navbar-nav navbar-right">
			<li><a href="/logout">Logout</a></li>
		</ul>
	</div>

</nav>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>
<div class="container">
	Application has encountered an error. Please contact support on ...
</div>

<%@ include file="common/footer.jspf"%>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>

<div class="container">
	<table class="table table-striped">
		<caption>Your Todos are</caption>
		<thead>
			<tr>
				<th>Description</th>
				<th>Date</th>
				<th>Completed</th>
				<th></th>
			</tr>
		</thead>
		<tbody>
			<c:forEach items="${todos}" var="todo">
				<tr>
					<td>${todo.desc}</td>
					<td><fmt:formatDate pattern="dd/MM/yyyy"
							value="${todo.targetDate}" /></td>
					<td>${todo.done}</td>
					<td><a type="button" class="btn btn-primary"
						href="/update-todo?id=${todo.id}">Edit</a> <a type="button"
						class="btn btn-warning" href="/delete-todo?id=${todo.id}">Delete</a>
					</td>
				</tr>
			</c:forEach>
		</tbody>
	</table>
	<div>
		<a type="button" class="btn btn-success" href="/add-todo">Add</a>
	</div>
</div>
<%@ include file="common/footer.jspf"%>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>
<div class="container">
	<form:form method="post" commandName="todo">
		<form:hidden path="id" />
		<fieldset class="form-group">
			<form:label path="desc">Description</form:label>
			<form:input path="desc" type="text" class="form-control"
				required="required" />
			<form:errors path="desc" cssClass="text-warning" />
		</fieldset>
		<fieldset class="form-group">
			<form:label path="targetDate">Target Date</form:label>
			<form:input path="targetDate" type="text" class="form-control"
				required="required" />
			<form:errors path="targetDate" cssClass="text-warning" />
		</fieldset>
		<button type="submit" class="btn btn-success">Submit</button>
	</form:form>
</div>

<%@ include file="common/footer.jspf"%>

<script>
	$('#targetDate').datepicker({
		format : 'dd/mm/yyyy'
	});
</script>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>
<div class="container">
	Welcome ${name}. You are now authenticated.
</div>

<%@ include file="common/footer.jspf"%>

/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>
    
   <filter>
    		<filter-name>springSecurityFilterChain</filter-name>
    		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
   </filter>
 
   <filter-mapping>
   		<filter-name>springSecurityFilterChain</filter-name>
    		<url-pattern>/*</url-pattern>
   </filter-mapping> 
   
    <error-page>
	    <location>/WEB-INF/views/error.jsp</location>
	</error-page>
</web-app>