Spring MVC Web 应用程序：找不到默认构造函数

Question

Project ZIP: http://goo.gl/ddhLg5

---

Spring web app cannot be executed giving HTTP Status 500 error. It also writes out that No default constructor found for DSLR but in fact there is a default constructor. Maybe it has to do with application context or the way my beans declared? What is the reason my application cannot start?

DSLR:

 package main.java.com.springapp.mvc.model;

    public class DSLR {

    public DSLR() {
    }
    public void init() {}

    private int dslrId;
    private String model;
    private int price;
    private String description;

    public int getDslrId() {
        return dslrId;
    }

    public void setDslrId(int dslrId) {
        this.dslrId = dslrId;
    }

    public String getModel() {
        return model;
    }

    public void setModel(String model) {
        this.model = model;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public String toString() {
        return "DSLR [dslr=" + dslrId + ", model=" + model
                + ", price=" + price+ ", description=" + description+"]";
    }
}

web.xml

<web-app version="2.4"
                   xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<display-name>Spring MVC Application</display-name>

<servlet>
    <servlet-name>mvc-dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

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

DSLRServletController-servlet.xml:

 <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:context="http://www.springframework.org/schema/context"
           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-3.0.xsd
       http://www.springframework.org/schema/context 
       http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan base-package="main.java.com.springapp.mvc" >
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/" />
        <property name="suffix" value=".jsp" />
    </bean>


    <bean name="s" class="main.java.com.springapp.mvc.controller.DSLRServletController">
        <property  name="dslrDAO" ref="dslrDAO" />
        <property  name="DSLR" ref="DSLR" />
    </bean>
    <bean id="dslrDAO" class="main.java.com.springapp.mvc.dao.DSLRDAO">

    </bean>
    <bean id="DSLR" class="main.java.com.springapp.mvc.model.DSLR">

    </bean>


</beans>

mvc-dispatcher-servlet.xml

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

    <context:component-scan base-package="main.java.com.springapp.mvc"/>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

</beans>

ERROR:

HTTP Status 500 - Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]: No default constructor found; nested exception is java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()

type Exception report

message Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]: No default constructor found; nested exception is java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]: No default constructor found; nested exception is java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:927)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]: No default constructor found; nested exception is java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()
    org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:108)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveModelAttribute(HandlerMethodInvoker.java:770)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:363)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171)
    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:439)
    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:427)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()
    java.lang.Class.getConstructor0(Class.java:2810)
    java.lang.Class.getDeclaredConstructor(Class.java:2053)
    org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:105)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveModelAttribute(HandlerMethodInvoker.java:770)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:363)
    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171)
    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:439)
    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:427)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:811)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.52 logs.

---

Main controller class:

package main.java.com.springapp.mvc.controller;

import main.java.com.springapp.mvc.dao.DSLRDAO;
import main.java.com.springapp.mvc.model.DSLR;
import main.java.com.springapp.mvc.pckg.DSLRForm;
import main.java.com.springapp.mvc.pckg.DSLRValidaor;
import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.Serializable;
import java.util.*;

@Controller
public class DSLRServletController extends HttpServlet  {
    static Logger logger = Logger.getLogger(DSLRServletController.class);

    private DSLR DSLR;
    private DSLRDAO dslrDAO;
    private DSLR dslr;

   /* request.setCharacterEncoding("UTF-8");
    response.setContentType("text/html; charset=utf-8");
    List list = getActions(request, response);
    response.setContentType("text/html; charset=UTF-8");*/

    //@Autowired   ???
    public DSLRServletController() {
        this.dslrDAO = new DSLRDAO();
    }

    public void init() {logger.error("DSLRServlet.init(): just started"); }
    /*
            /s                                    GET
            /s?id=1                               GET
            /s?action=save                        POST
            /dslrservice?id=1&tm=<timestamp>      GET
     */
@RequestMapping(value = "/s", method = RequestMethod.GET)
public String showHTMLResponse(@ModelAttribute("dslrs") DSLR dslrs[],
                               @ModelAttribute("dslr") DSLR dslr,
                               @ModelAttribute("dslrErrors") HashMap dslrErrors,
                               @ModelAttribute ("dslrform") DSLRForm dslrForm,
                               @RequestParam("id") String paramId,
                               @RequestParam("action") String paramAction,
                               Model model){

    if(paramId == null || paramId.equals("")){
        //show_all_dslrs
        dslrs = getAllDslrs();    // DSLR adslrs[] -> to MODEL;
       return "dslrs";
    }else{
        //show_this_dslr;
        HashMap<String,Object> dslrHashMap = getDSLRById(paramId);
        dslr = (DSLR) dslrHashMap.get("dslr");
        dslrForm = (DSLRForm)dslrHashMap.get("dslrForm");
        dslrErrors = (HashMap)dslrHashMap.get("dslrErrors");

            if(dslr != null){
//                getServletConfig().getServletContext().getRequestDispatcher("/dslr.jsp").forward(request, response);
                return "dslr";
            }

            else{
                return "error";
            }


    }
}

@RequestMapping(value = "/s", method = RequestMethod.POST)
public String showHTMLResponsePOST(@ModelAttribute("dslrs") DSLR dslrs[],
                               @ModelAttribute("dslrErrors") HashMap<?,?> dslrErrors,
                               @ModelAttribute ("dslrform") DSLRForm dslrForm,

                               @RequestParam("id") String paramId,
                               @RequestParam("action") String paramAction,
                               @RequestParam("dslr_model") String paramModel,
                               @RequestParam("price") String paramPrice,
                               @RequestParam("description") String paramDescription,
                               Model model){
    int iStatusCode = 0;
    if(paramAction.equals("save") )
        iStatusCode = saveDSLR(paramId, paramModel, paramPrice, paramDescription, dslrErrors, dslrForm);    // POST

    return "dslrs";

}

    private int saveDSLR(String paramId,
                         String paramModel,
                         String paramPrice,
                         String paramDescription,
                         HashMap<?,?> context_dslrErrors,
                         DSLRForm context_dslrForm
                         ) {
        int byte0 = 1;
        try {

            DSLRValidaor dslrValidaor = new DSLRValidaor();

            DSLRForm dslrForm = new DSLRForm();
            dslrForm.setDslrId(paramId);
            dslrForm.setModel(paramModel);
            dslrForm.setPrice(paramPrice);
            dslrForm.setDescription(paramDescription);

            HashMap hashmap = dslrValidaor.Validate(dslrForm);
            if(hashmap.size() > 0) {
                context_dslrForm = dslrForm;
                context_dslrErrors = hashmap;
                byte0 = -1;
            } else{
                DSLRDAO planedao = new DSLRDAO();
                DSLR dslr = new DSLR();
                dslr.setDslrId(Integer.parseInt(paramId));
                dslr.setModel(paramModel);
                dslr.setPrice(Integer.parseInt(paramPrice));
                dslr.setDescription(paramDescription);
                planedao.update(dslr);
            }
        }
        catch(Exception exception)
        {
            logger.error((new StringBuilder()).append("DSLRServlet.saveDSLR():").append(exception.getMessage()).toString());
            byte0 = -1;
        }
        return byte0;

    }

    private DSLR[] getAllDslrs(){
        DSLR adslrs[] = null;
        try
        {
            DSLRDAO DSLRDAO = new DSLRDAO();
            adslrs = (DSLR[])DSLRDAO.findAll();
        }
        catch(Exception exception)
        {
            logger.error((new StringBuilder()).append("PlaneServlet.getAllPlanes():").append(exception.getMessage()).toString());
        }
//        request.setAttribute("dslrs", adslrs);
        return adslrs;
    }

    private HashMap<String, Object> getDSLRById(String s)
    {
        HashMap<String,Object> map = new HashMap<String, Object>();

        DSLR dslr = null;
        try {
            int i = Integer.parseInt(s);
            DSLRDAO DSLRDAO = new DSLRDAO();
            dslr = (DSLR)DSLRDAO.findById(i);

            DSLRForm dslrForm = new DSLRForm();
            dslrForm.setDslrId(Integer.toString(dslr.getDslrId()));
            dslrForm.setModel(dslr.getModel());
            dslrForm.setPrice(Integer.toString(dslr.getPrice()));
            dslrForm.setDescription(dslr.getDescription());


            map.put("dslr", dslr);
            map.put("dslrform", dslrForm);
            map.put("dslrErrors", new HashMap());
        }
        catch(Exception exception)
        {
            logger.error((new StringBuilder()).append("DSLRServlet.getDSLRById():").append(exception.getMessage()).toString());
        }
        return map;
    }

    public void setDslrDAO(DSLRDAO dslrDAO) {
        this.dslrDAO = dslrDAO;
    }

    public DSLRDAO getDslrDAO() {
        return dslrDAO;
    }

    public void setDSLR(main.java.com.springapp.mvc.model.DSLR DSLR) {
        dslr = DSLR;
    }

    public main.java.com.springapp.mvc.model.DSLR getDSLR() {
        return dslr;
    }
}

---

UPDATE1:

new mvc-dispatcher-servlet.xml:

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

    <context:component-scan base-package="main.java.com.springapp.mvc" >
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

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

And @Autowired was put in DSLRServletController:

@Autowired
    public DSLRServletController() {
        this.dslrDAO = new DSLRDAO();
    }

Errors:

exception

javax.servlet.ServletException: Servlet.init() for servlet mvc-dispatcher threw exception
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    java.lang.Thread.run(Thread.java:744)
root cause

java.lang.IllegalStateException: Autowired annotation requires at least one argument: public main.java.com.springapp.mvc.controller.DSLRServletController()
    org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.determineCandidateConstructors(AutowiredAnnotationBeanPostProcessor.java:243)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineConstructorsFromBeanPostProcessors(AbstractAutowireCapableBeanFactory.java:976)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:949)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:490)
    org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:607)
    org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:647)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:598)
    org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:661)
    org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:517)
    org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:458)
    org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:138)
    javax.servlet.GenericServlet.init(GenericServlet.java:158)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
    java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    java.lang.Thread.run(Thread.java:744)

For some reason 2 errors appeared. What should be changed to set up project correctly?

---

UPDATE3

the new mvc-dispatcher-servlet.xml:

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

    <context:component-scan base-package="main.java.com.springapp.mvc" >
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/"/>
        <property name="suffix" value=".jsp"/>
    </bean>
    <bean id="DSLR" class="main.java.com.springapp.mvc.model.DSLR" />
</beans>

Apart from @Autowired added in UPDATE1 , another one is added (in DSLRServletController ):

@Autowired
    public void setDSLR(DSLR DSLR) {
        dslr = DSLR;
    }

---

UPDATE4:

Back to the original errors : Could not instantiate bean class [[Lmain.java.com.springapp.mvc.model.DSLR;]

I am confused. What's wrong?

Answer 1

Inside your controller method , you have used a parameter as array like below

@ModelAttribute("dslrs") DSLR dslrs[]

so use collection like list instead

@ModelAttribute("dslrs") ArrayList<DSLR> dslrs

Answer 2

This is the error message you would get if DSLR had no default constructor:

java.lang.NoSuchMethodException: main.java.com.springapp.mvc.model.DSLR.<init>()

Now compare this to your error message:

java.lang.NoSuchMethodException: [Lmain.java.com.springapp.mvc.model.DSLR;.<init>()

Do you notice the difference? The [L ? The error means that you cannot instantiate an array with a constructor, because an array has no constructor. That's why you can't use an array as a parameter for your controller method. At least not that way. Use a collection and you are fine.

Answer 3

I note a little redundancy. It shouldn't, by itself, cause these problems, but it may be worth exploring:

You use <context:component-scan base-package="main.java.com.springapp.mvc" > , which seems like it's intended to load your @Controller -annotated DSLRServletController . If that is the case, then there is no need to declare the bean named s in your XML configuration. You can simply put @Autowired on the bean property setters. Alternatively, you can remove the <context:component-scan> from your XML configuration, and trust your delcaration of the controller to be sufficient.

Additionally, though it's probably not related. If you load something using @Controller and classpath annotation scanning, you don't need to implement HttpServlet at all. The point of @Controller and Spring MVC is to make it so that your controllers can be Plain Old Java Objects (POJOs).

Most importantly, it looks like your web.xml is only causing mvc-dispatcher-servlet.xml to be loaded (by using the servlet name as a hint), and nothing is loading DSLRServletController-servlet.xml . A consequence of this, is that your <context:component-scan base-package="main.java.com.springapp.mvc"/> is causing the controller to be loaded, but none of it's properties are being set. To further clean up your system, move your DSLRServletController-servlet.xml into mvc-dispatcher-servlet.xml so that your spring contexts are configured from a single config.

Answer 4

I got the same issue while running Spring boot application using Apache Tomcat 9.0. Now, I have resolved this.

1. I have commented two lines as below. (ie, whatever you have used here, just comment and run).then it will work.

    @RequestMapping("/userhome") public String userhome(Model model) { System.out.println("inside bck..."); //List<String> colorList = colorList();`enter code here` //model.addAttribute("theme", colorList); //model.addAttribute("home", new UserHome()); return "userhomePage"; }

Answer 5

In my case the problem was not that there is not default constructor. The issue was that there were no setters for fields of the json DTO that is passed to the controller in a rest post call.