java – Spring MVC Web应用程序：找不到默认构造函数

无法执行Spring Web应用程序,从而出现HTTP Status 500错误.它还写出没有为DSLR找到默认构造函数,但实际上有一个默认构造函数.也许它与应用程序上下文或我的bean声明的方式有关？我的申请无法启动的原因是什么？

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中

display-name>Spring MVC Applicationdisplay-name>

dispatcherdispatcherServletservlet-mapping>
    dispatcherservlet-mapping>


DSlrservletController-servlet.xml中：

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

    lrservletController">
        

MVC-调度-servlet.xml中

spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    

错误：

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;.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;.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;.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;.modelattribute(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;.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.

主控制器类：

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=@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;
        HashMaparamId);
        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") HashMaparam("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,HashMaparamId);
            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 HashMaplrservlet.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：
新的mvc-dispatcher-servlet.xml：

spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    

并且@Autowired被放入DSlrservletController：

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

错误：

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)

出于某种原因出现了2个错误.应该更改什么才能正确设置项目？
UPDATE3
新的mvc-dispatcher-servlet.xml：

spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

    

除了在UPDATE1中添加的@Autowired之外,还添加了另一个(在DSlrservletController中)：

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

UPDATE4：
回到原始错误：无法实例化bean类[[Lmain.java.com.springapp.mvc.model.DSLR;]
我很迷惑.怎么了？


最佳答案
在您的控制器方法中,您已将参数用作如下所示的数组

@modelattribute("dslrs") DSLR dslrs[]

所以使用像list这样的集合

@modelattribute("dslrs") ArrayListlrs



                
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java – Spring MVC Web应用程序：找不到默认构造函数

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