关于Spring Boot Rest API和Javascript Ajax呼叫通信的问题

Question

After login, I connect to home page automatically. When the button is pressed, I want to access the 'findAllUsers' method on the controller in the spring boot and display the registered users in a table format. I used ajax get call for this. But I get the console error I mentioned in the photo below. What do I need to change? What should I do?

USER.java

@Data
@Entity
@Table(name = "user")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "user_id")
    private int id;
    @Column(name = "email")
    @Email(message = "*Please enter a valid Email")
    @NotEmpty(message = "*Please provide an email")
    private String email;
    @Column(name = "password")
    @Length(min = 5, message = "*Your password must have at least 5 characters")
    @NotEmpty(message = "*Please enter your password")
    private String password;
    @Column(name = "name")
    @NotEmpty(message = "*Please enter your name")
    private String name;
    @Column(name = "last_name")
    @NotEmpty(message = "*Please enter your last name")
    private String lastName;
    @Column(name = "active")
    private int active;
    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private Set<Role> roles;

    //G&S
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public int getActive() {
        return active;
    }
    public void setActive(int active) {
        this.active = active;
    }
    public Set<Role> getRoles() {
        return roles;
    }
    public void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
}

Service.java

@Service
public class UserService {

    private UserRepository userRepository;
    private RoleRepository roleRepository;
    private BCryptPasswordEncoder bCryptPasswordEncoder;

    @Autowired
    public UserService(UserRepository userRepository,
                       RoleRepository roleRepository,
                       BCryptPasswordEncoder bCryptPasswordEncoder) {

        this.userRepository = userRepository;
        this.roleRepository = roleRepository;
        this.bCryptPasswordEncoder = bCryptPasswordEncoder;
    }

    public List<User> findAllUsers(){
        return userRepository.findAll();
    }

    public User findUserByEmail(String email) {
        return userRepository.findByEmail(email);
    }

    public List<User> findByName(String name){
        return userRepository.findByName(name);
    }

    public List<User> findByLastName(String lastName){
        return userRepository.findByLastName(lastName);
    }

    //CREATE USER
    public User saveUser(User user) {
        user.setPassword(bCryptPasswordEncoder.encode(user.getPassword()));
        user.setActive(1);
        Role userRole = roleRepository.findByRole("ADMIN");
        user.setRoles(new HashSet<Role>(Arrays.asList(userRole)));
        return userRepository.save(user);
    }
}

Controller.java

@Controller
public class LoginController {

    @Autowired
    private UserService userService;

    //LOGIN
    @RequestMapping(value={"/", "/login"}, method = RequestMethod.GET)
    public ModelAndView login(){
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("login");
        return modelAndView;
    }

    //REGISTRATION GET
    @RequestMapping(value="/registration", method = RequestMethod.GET)
    public ModelAndView registration(){
        ModelAndView modelAndView = new ModelAndView();
        User user = new User();
        modelAndView.addObject("user", user);
        modelAndView.setViewName("registration");
        return modelAndView;
    }

    //REGISTRATION POST
    @RequestMapping(value = "/registration", method = RequestMethod.POST)
    public ModelAndView createNewUser(@Valid User user, BindingResult bindingResult) {
        ModelAndView modelAndView = new ModelAndView();
        User userExists = userService.findUserByEmail(user.getEmail());
        if (userExists != null) {
            bindingResult
                    .rejectValue("email", "error.user",
                            "There is already a user registered with the email provided");
        }
        if (bindingResult.hasErrors()) {
            modelAndView.setViewName("registration");
        } else {
            userService.saveUser(user);
            modelAndView.addObject("successMessage", "Registered successfully");
            modelAndView.addObject("user", new User());
            modelAndView.setViewName("registration");

        }
        return modelAndView;
    }

    //HOME PAGE
    @RequestMapping(value="/admin/home", method = RequestMethod.GET)
    public ModelAndView home(){
        ModelAndView modelAndView = new ModelAndView();
        Authentication auth = SecurityContextHolder.getContext().getAuthentication();
        User user = userService.findUserByEmail(auth.getName());
        modelAndView.addObject("userName", "Welcome " + user.getName() + " " + user.getLastName() + " (" + user.getEmail() + ")");
        modelAndView.addObject("adminMessage","Content Available Only for Users with Admin Role");
        modelAndView.setViewName("admin/home");
        return modelAndView;
    }

    //GET ALL USERS
    @RequestMapping(value="/findAllUsers", method = RequestMethod.GET)
    public List<User> findAllUsers(){
        return userService.findAllUsers();
    }
}

login.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://www.thymeleaf.org">

<head>
    <title>Spring Security Tutorial</title>
    <link rel="stylesheet" type="text/css" th:href="@{/css/login.css}"/>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>

<body>

<div class="container">
    <img th:src="@{/images/login.png}" class="img-responsive center-block" width="170" height="170" alt="Logo"/>
    <form th:action="@{/login}" method="POST" class="form-signin">
        <h3 class="form-signin-heading" th:text="Welcome"></h3>
        <br/>

        <input type="text" id="email" name="email" th:placeholder="Email"
               class="form-control"/> <br/>
        <input type="password" th:placeholder="Password"
               id="password" name="password" class="form-control"/> <br/>

        <div align="center" th:if="${param.error}">
            <p style="font-size: 20; color: #FF1C19;">Email or Password invalid, please verify</p>
        </div>
        <button class="btn btn-lg btn-primary btn-block" name="Submit" value="Login" type="Submit"
                th:text="Login"></button>
    </form>
        <form th:action="@{/registration}" method="get" class="form-signin">
         <button class="btn btn-md btn-warning btn-block" type="Submit">Registration</button>
        </form>
</div>
</body>
</html>

home.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:th="http://www.thymeleaf.org">

<head>
    <title>Admin Panel</title>
    <link rel="stylesheet" type="text/css" th:href="@{/css/home.css}"/>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
    <script src="/js/getUsers.js"></script>
</head>

<body>
<div class="container">

    <form th:action="@{/logout}" method="get" class="logout">
        <button class="btn btn-md btn-danger btn-block" name="registration"
                type="Submit">Logout
        </button>
    </form>

    <div class="panel-group" style="margin-top:40px">
        <div class="panel panel-primary">
            <div class="panel-heading">
                <span th:utext="${userName}"></span>
            </div>
            <div class="panel-body">
            </div>
            <p class="admin-message-text text-center" th:utext="${adminMessage}"></p>
        </div>
    </div>
    <!-- USERS DETAILS -->
  <div class="col-sm-7" style="margin:20px 0px 20px 0px">
      <button id="getAllUsers">Get users details</button>
      <div id="getResultDiv1" style="padding:20px 10px 20px 50px">
            <ul class="list-group">
          </ul>
        </div>
      </div>
    </div>

</div>
</body>
</html>

ajax get request

$( document ).ready(function() {

    $("#getAllUsers").click(this.disabled=1,function(event){
        event.preventDefault();
        ajaxGet();
    });

    function ajaxGet(){
        $.ajax({
            type : "GET",
            url :  "http://localhost:8080/findAllUsers/",
            dataType : 'json', 
            contentType:'application/x-www-form-urlencoded',

            success: function(result){
                alert("Users have loaded!");
                $('#getResultDiv1 ul').empty();
                var tableTitle = "<h2><strong>Users List</strong></h2>";
                var userList = "<table border='1'>";
                userList += "<tr><td><strong>Name</strong></td><td><strong>Surname</strong></td><td><strong>E-Mail</strong></td></tr>";

                $.each(result, function(i, users){
                    userList +="<tr>";
                    userList +="<td>"+users.name +"</td>";
                    userList +="<td>"+users.lastName+"</td>";
                    userList +="<td>"+users.email+"</td>";
                    userList +="</tr>";
                });
                userList +="</table>";
                $('#getResultDiv1').append(tableTitle, userList)
                console.log("Success: ", result);
        },
            error : function(e) {
                $("#getResultDiv1").html("<strong>Something went wrong</strong>");
                console.log("Something went wrong: ", e);
            }
        }); 
    }
})

Console Log Project Structure

Spring error logs:

org.thymeleaf.exceptions.TemplateInputException: Error resolving template [findAllUsers], template might not exist or might not be accessible by any of the configured Template Resolvers
    at org.thymeleaf.engine.TemplateManager.resolveTemplate(TemplateManager.java:869) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:607) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1098) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1072) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.view.ThymeleafView.renderFragment(ThymeleafView.java:362) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.view.ThymeleafView.render(ThymeleafView.java:189) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1371) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1117) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1056) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:320) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:119) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:116) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:74) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:334) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:215) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:178) ~[spring-security-web-5.1.5.RELEASE.jar:5.1.5.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:357) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:270) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:109) ~[spring-web-5.1.8.RELEASE.jar:5.1.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.8.0_221]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.8.0_221]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.21.jar:9.0.21]
    at java.lang.Thread.run(Unknown Source) [na:1.8.0_221]

Answer 1

Anotate the controller method to return application/json mime type.

@RequestMapping(value="/findAllUsers", method = RequestMethod.GET, produces={ "application/json"})
    public List<User> findAllUsers(){
        return userService.findAllUsers();
    }