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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
  • Whitelabel Error Page provided by default by Spring Boot
  • You can see a few details of the errors
  • We can customize if we would want to
  • @ControllerAdvice and Controller Specific Exception Handling
  • Handling Errors thrown from Views

Useful Snippets

@Controller("error")
public class ExceptionController {

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

    @ExceptionHandler(Exception.class)
    public ModelAndView handleError(HttpServletRequest req, Exception ex) {
        logger.error("Request: " + req.getRequestURL() + " raised " + ex);

        ModelAndView mav = new ModelAndView();
        mav.addObject("exception", ex);
        mav.addObject("url", req.getRequestURL());
        mav.setViewName("error");
        return mav;
    }
}

Files List

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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.springboot.web</groupId>
	<artifactId>spring-boot-first-web-application</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>spring-boot-first-web-application</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.4.3.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-security</artifactId>
		</dependency>

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

		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>bootstrap</artifactId>
			<version>3.3.6</version>
		</dependency>
		
		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>bootstrap-datepicker</artifactId>
			<version>1.0.1</version>
		</dependency>
		
		<dependency>
			<groupId>org.webjars</groupId>
			<artifactId>jquery</artifactId>
			<version>1.9.1</version>
		</dependency>

		<dependency>
			<groupId>org.apache.tomcat.embed</groupId>
			<artifactId>tomcat-embed-jasper</artifactId>
			<scope>provided</scope>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-devtools</artifactId>
			<scope>runtime</scope>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

src/main/java/com/in28minutes/springboot/web/controller/ErrorController.java

package com.in28minutes.springboot.web.controller;

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

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;

@Controller("error")
public class ErrorController {
	
	@ExceptionHandler(Exception.class)
	public ModelAndView handleException
		(HttpServletRequest request, Exception ex){
		ModelAndView mv = new ModelAndView();

		mv.addObject("exception", ex.getLocalizedMessage());
		mv.addObject("url", request.getRequestURL());
		
		mv.setViewName("error");
		return mv;
	}

}

src/main/java/com/in28minutes/springboot/web/controller/LogoutController.java

package com.in28minutes.springboot.web.controller;

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.core.userdetails.UserDetails;
import org.springframework.security.web.authentication.logout.LogoutHandler;
import org.springframework.security.web.authentication.logout.SecurityContextLogoutHandler;
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 LogoutController {

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

		return "redirect:/";
	}
}

src/main/java/com/in28minutes/springboot/web/controller/TodoController.java

package com.in28minutes.springboot.web.controller;

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.springboot.web.model.Todo;
import com.in28minutes.springboot.web.service.TodoService;

@Controller
public class TodoController {

	@Autowired
	TodoService service;

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

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

	private String getLoggedInUserName(ModelMap model) {
		Object principal = SecurityContextHolder.getContext()
				.getAuthentication().getPrincipal();
		
		if (principal instanceof UserDetails) {
			return ((UserDetails) principal).getUsername();
		}
		
		return principal.toString();
	}

	@RequestMapping(value = "/add-todo", method = RequestMethod.GET)
	public String showAddTodoPage(ModelMap model) {
		model.addAttribute("todo", new Todo(0, getLoggedInUserName(model),
				"Default Desc", new Date(), false));
		return "todo";
	}

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

		if(id==1)
			throw new RuntimeException("Something went wrong");
		
		service.deleteTodo(id);
		return "redirect:/list-todos";
	}

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

		service.updateTodo(todo);

		return "redirect:/list-todos";
	}

	@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(model), todo.getDesc(), todo.getTargetDate(),
				false);
		return "redirect:/list-todos";
	}
}

src/main/java/com/in28minutes/springboot/web/controller/WelcomeController.java

package com.in28minutes.springboot.web.controller;

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/java/com/in28minutes/springboot/web/model/Todo.java

package com.in28minutes.springboot.web.model;

import java.util.Date;

import javax.validation.constraints.Size;

public class Todo {
    private int id;
    private String user;
    
    @Size(min=10, message="Enter at least 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/springboot/web/security/SecurityConfiguration.java

package com.in28minutes.springboot.web.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.WebSecurityConfigurerAdapter;

@Configuration
public class SecurityConfiguration extends WebSecurityConfigurerAdapter{
	//Create User - in28Minutes/dummy
	@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/springboot/web/service/TodoService.java

package com.in28minutes.springboot.web.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.springboot.web.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().equalsIgnoreCase(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/springboot/web/SpringBootFirstWebApplication.java

package com.in28minutes.springboot.web;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@ComponentScan("com.in28minutes.springboot.web")
public class SpringBootFirstWebApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootFirstWebApplication.class, args);
	}
}

src/main/resources/application.properties

spring.mvc.view.prefix=/WEB-INF/jsp/
spring.mvc.view.suffix=.jsp
logging.level.org.springframework.web=INFO

src/main/webapp/WEB-INF/jsp/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>
<script>
	$('#targetDate').datepicker({
		format : 'dd/mm/yyyy'
	});
</script>

</body>
</html>

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

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>

<html>

<head>
<title>First Web Application</title>
<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
	rel="stylesheet">

</head>

<body>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>
<div class="container">
An exception occurred! Please contact Support!
</div>
<%@ include file="common/footer.jspf"%>

src/main/webapp/WEB-INF/jsp/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>Target Date</th>
					<th>Is it Done?</th>
					<th></th>
					<th></th>
				</tr>
			</thead>
			<tbody>
				<c:forEach items="${todos}" var="todo">
					<tr>
						<td>${todo.desc}</td>
						<td><fmt:formatDate value="${todo.targetDate}" pattern="dd/MM/yyyy"/></td>
						<td>${todo.done}</td>
						<td><a type="button" class="btn btn-success"
							href="/update-todo?id=${todo.id}">Update</a></td>
						<td><a type="button" class="btn btn-warning"
							href="/delete-todo?id=${todo.id}">Delete</a></td>
					</tr>
				</c:forEach>
			</tbody>
		</table>
		<div>
			<a class="button" href="/add-todo">Add a Todo</a>
		</div>
	</div>
<%@ include file="common/footer.jspf" %>

src/main/webapp/WEB-INF/jsp/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">Add</button>
	</form:form>
</div>
<%@ include file="common/footer.jspf" %>

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

<%@ include file="common/header.jspf"%>
<%@ include file="common/navigation.jspf"%>
<div class="container">
	Welcome ${name}!! <a href="/list-todos">Click here</a> to manage your
	todo's.
</div>
<%@ include file="common/footer.jspf"%>

src/test/java/com/in28minutes/springboot/web/SpringBootFirstWebApplicationTests.java

package com.in28minutes.springboot.web;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBootFirstWebApplicationTests {

	@Test
	public void contextLoads() {
	}

}

todo.txt

Implementing Server Side Validation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Command Bean or Form Backing Bean

Add Validation
Use Validation on Controller
Display Errors in View

Command Bean
~~~~~~~~~~~~
Controller
View - Spring Form Tags



LoginController -> adds name to model
welcome.jsp -> shows ${name}

TodoController -> redirects to list-todos.jsp
${name} is empty 


Component, Service, Repository, Controller
Autowired
ComponentScan

Field dummyService in com.in28minutes.springboot.web.controller.LoginController 
required a bean of type 'com.in28minutes.dummy.DummyService' 
that could not be found.

Spring Boot Starter Parent
Spring Boot Starter Web
@SpringBootApplication
Auto Configuration

Dispatcher Servlet

/login => "login"

"login" => src/main/webapp/WEB-INF/jsp/login.jsp 


Search for a view named "login"



/login => LoginController