Why error is coming after adding javascript , bootstrap and CSS path in list-todos.jsp

Question

I am working on spring-boot project. Code is working fine until I add javascript , bootstrap and CSS path in list-todos.jsp but after I add them and hit URL "http://localhost:8080/list-todos", it is giving error (NullPointerException). Also, if I remove those paths it is working fine.

list-todos.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<html>

<head>
<title> Todo's for ${name}</title>
<link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
                rel="stylesheet">
</head>

<body>
   <H1>Your Todos</H1>
   <table>
      <caption>Your todos are</caption>
      <thead>
           <tr>
               <th>Description</th>
               <th>Target Date</th>
               <th>Is it Done?</th>
           </tr>
      </thead>
      <tbody>
         <c:forEach items="${todos}" var="todo">
           <tr>
              <td>${todo.desc}</td>
              <td>${todo.targetDate}</td>
              <td>${todo.done}</td>
           </tr>
         </c:forEach>
      </tbody>
   </table>
   
  
  <Br/>
  <a href = "/add-todo">Add a Todo</a>
  
  
    <script src="webjars/jquery/1.9.1/jquery.min.js"></script>
    <script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
        
        
</body>

TodoController.java

package com.in28minutes.springboot.web.controller;

import java.util.Date;

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;

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



@Controller
@SessionAttributes("name")
public class TodoController {
    
    
    @Autowired
    TodoService service;
    
    @RequestMapping(value="/list-todos", method = RequestMethod.GET)
    public String showTodos( ModelMap model  ) {
        String name = (String) model.get("name");
        model.put("todos", service.retrieveTodos(name));
        return "list-todos";
    }
    
    @RequestMapping(value="/add-todo", method = RequestMethod.GET)
    public String showAddTodos( ModelMap model  ) {
        return "todo";
    }
    

    @RequestMapping(value="/add-todo", method = RequestMethod.POST)
    public String addTodo(ModelMap model, @RequestParam String desc){
        service.addTodo((String) model.get("name"), desc, new Date(), false);
        return "redirect:/list-todos";
    }
    }

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, "Rajeev", "Learn Spring MVC", new Date(),
                false));
        todos.add(new Todo(2, "Rajeev", "Learn Struts", new Date(), false));
        todos.add(new Todo(3, "Rajeev", "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();
            }
        }
    }
}

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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.7</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.in28minutes.springboot.web</groupId>
    <artifactId>spring-boot-first-web-application</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-first-web-application</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>13.0.2</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>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>
            <optional>true</optional>
        </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>

Error in Compiler

 : Forwarding to [/WEB-INF/jsp/todo.jsp]
2022-05-14 13:39:49.257 DEBUG 3120 --- [nio-8080-exec-5] o.s.web.servlet.DispatcherServlet        : Completed 200 OK
2022-05-14 13:39:52.036 DEBUG 3120 --- [nio-8080-exec-6] o.s.web.servlet.DispatcherServlet        : POST "/add-todo", parameters={masked}
2022-05-14 13:39:52.037 DEBUG 3120 --- [nio-8080-exec-6] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to com.in28minutes.springboot.web.controller.TodoController#addTodo(ModelMap, String)
2022-05-14 13:39:52.046 DEBUG 3120 --- [nio-8080-exec-6] o.s.web.servlet.view.RedirectView        : View name 'redirect:', model {}
2022-05-14 13:39:52.048 DEBUG 3120 --- [nio-8080-exec-6] o.s.web.servlet.DispatcherServlet        : Completed 302 FOUND
2022-05-14 13:39:52.053 DEBUG 3120 --- [nio-8080-exec-7] o.s.web.servlet.DispatcherServlet        : GET "/list-todos", parameters={}
2022-05-14 13:39:52.053 DEBUG 3120 --- [nio-8080-exec-7] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped to com.in28minutes.springboot.web.controller.TodoController#showTodos(ModelMap)
2022-05-14 13:39:52.057 DEBUG 3120 --- [nio-8080-exec-7] o.s.web.servlet.DispatcherServlet        : Failed to complete request: java.lang.NullPointerException
2022-05-14 13:39:52.067 ERROR 3120 --- [nio-8080-exec-7] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

java.lang.NullPointerException: null

Path

Error in Browser

Paths, These path if I am removing them, code is working fine.

<script src="webjars/jquery/1.9.1/jquery.min.js"></script>
        <script src="webjars/bootstrap/3.3.6/js/bootstrap.min.js"></script>
        <link href="webjars/bootstrap/3.3.6/css/bootstrap.min.css"
                rel="stylesheet">

Please let me know, if any additional information required. Please help me with the issue.

The `NullPointerException` is thrown in the `TodoService` on line 28 - can you provide this code too? — Jelmen, May 14 '22 at 11:49

Why error is coming after adding javascript , bootstrap and CSS path in list-todos.jsp

0 Answers0