Question

我正在开发一个SpringMVC 3琐碎的应用程序，但我被困在某个地方。本质上，在GET操作中填充字段的模型属性在POST中返回NULL（即使我不对它们进行任何操作）。我已经检查了这个和其他论坛，我提出的唯一答案是为我应该放入模型的类实现编辑器，这是一个初始化器，可用于注册自定义编辑器并使其可用于应用程序（在servletname-servlet.xml文件）。我做过的所有操作，但绝对没有运气。我想知道是否有人可以帮助我。谢谢。

以下控制器：

@Controller
@RequestMapping(value="/nourish")
public class NourishController {

private PetDAO pdao = new PetDAO();
private UserDAO udao = new UserDAO();
private FeedVirtualPet feedvp = new FeedVirtualPet();

@RequestMapping(method = RequestMethod.GET)
public String nourish(Model model, HttpServletRequest request){
    NourishPetDTO npdto = new NourishPetDTO();
    PetDTO      pdto=pdao.findPetByBusinessKey((PetDTO)request.getSession().getAttribute("pet"));
    npdto.setPet(pdto);
    npdto.setAmt(0);
    model.addAttribute("npdto", npdto);
    return "nourish";
}


@RequestMapping(method = RequestMethod.POST)
public String nourishPOST(@ModelAttribute("npdto") NourishPetDTO npdto,
        //BindingResult result,
        HttpServletRequest request){

    System.out.println("*****nourishPOST.npdto.amt: "+npdto.getAmt());
    System.out.println("*****nourishPOST.npdto.pet.petname: "+npdto.getPet().getPetName());
    System.out.println("*****nourishPOST.npdto.pet.hunger:     "+npdto.getPet().getHunger());
    PetDTO pdto = feedvp.feed(npdto.getPet(), npdto.getAmt());
    request.getSession().setAttribute("user", pdto.getOwner());
    return "redirect:detailPet";
}
}

具有GET和POST操作的方法，并且与以下jsp相关联 - 在此视图中，所有模型信息都通过EL正确显示：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" session="true"  pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Nourish your pet!!</title>
</head>
<body>
Your stats for <h3>${npdto.pet.petName}</h3><br>
    Please note that any value you put inside will:
        <ol>
            <li>Subtract value to your current hunger level</li>
            <li>Add (value) to your current health level</li>
        </ol>
    Please note that any value you'll put will in many manners "resized":
    <ol>
        <li>It must be even. If not, a default 0 value will be  applied</li>
        <li>It can't be greater than 4. If it's greater, the maxium value  of 4 will be anyway considered.</li>
        <li>If it ain't a number, a default zero value will be passed</li>
    </ol>
<table>
    <tr><td>Health</td><td>${npdto.pet.health}</td></tr>
    <tr><td>Hunger</td><td>${npdto.pet.hunger}</td></tr>
</table>
<form action="nourish" method="post"  >
    nourishment: <input type="text" name="amt"/>
    <input type="submit" value="Nourish!"/>
</form>
</body>
</html>

（请注意我没有使用返回NULL的模型属性，以确保我没有对它做任何事情）

POST操作在指令

上失败

System.out.println("*****nourishPOST.npdto.pet.petname:"+npdto.getPet().getPetName());

因为Tomcat返回NullPointerException。

如前所述，我一直在寻找这个问题的解决方案，我能找到的一切就是添加编辑器类和放大器。将编辑者注册到活页夹。结果仍然相同。

无论如何，这些是课程：

NourishPetEditor.java

public class NourishPetEditor extends PropertyEditorSupport {

private PetEditor pedit;

public PetEditor getPedit() {
    return pedit;
}


public NourishPetEditor() {
    // TODO Auto-generated constructor stub
    pedit =  new PetEditor();
}

@Override 
public String getAsText(){
    NourishPetDTO npdto= (NourishPetDTO)getValue();
    return super.getAsText()+","+npdto.getAmt();
}

public NourishPetDTO makeNourishPetDTOInstance(String [] parts){

    NourishPetDTO npdto = new NourishPetDTO(); 
    npdto.setPet(pedit.makePetDTOInstance(parts));
    npdto.setAmt(Integer.parseInt(parts[9]));
    return npdto;

}


public void setAsText(String key){
    String []parts = key.split(",");
    NourishPetDTO npdto = makeNourishPetDTOInstance(parts);
    setValue(npdto);
}
}

PetEditor.java

package com.virtualpet.dtoeditors;
import java.beans.PropertyEditorSupport;

import com.virtualpet.virtualpet_daos.PetDAO;  
import com.virtualpet.virtualpet_dtos.PetDTO;
import com.virtualpet.virtualpet_dtos.UserDTO;
public class PetEditor extends PropertyEditorSupport{

private PetDAO pdao;

public PetEditor() {
    // TODO Auto-generated constructor stub
}

public PetEditor(PetDAO pdao) {
    // TODO Auto-generated constructor stub
    this.pdao = pdao;

}


public String getAsText(){
    PetDTO pdto = (PetDTO) this.getValue();

    return pdto.getClass().getName()+","+ //0
    pdto.getPetName()+","+ //1
    pdto.getHealth()+","+  //2
    pdto.getHunger()+","+  //3
    pdto.getMood()+","+","+ //4
    pdto.getOwner().getClass().getName()+","+ //5
    pdto.getOwner().getUsername()+","+ //6
    pdto.getOwner().getEmail()+","+pdto.getOwner().getPassword(); //7,8

}

public void setAsText(String key) throws IllegalArgumentException {
    String []parts = key.split(",");
    PetDTO pdto = makePetDTOInstance(parts);
    setValue(pdto);
}


public UserDTO makeUserDTOInstance(String[] parts)
        throws InstantiationException, IllegalAccessException,
        ClassNotFoundException {

            UserDTO udto = (UserDTO)Class.forName(parts[5]).newInstance();
            udto.setUsername(parts[6]);
            udto.setEmail(parts[7]);
            udto.setPassword(parts[8]);
            return udto;
}


public PetDTO makePetDTOInstance(String[]parts){
    try{
        PetDTO pdto = (PetDTO) Class.forName(parts[0]).newInstance();
        pdto.setPetName(parts[1]);
        pdto.setHealth(Integer.parseInt(parts[2]));
        pdto.setHunger(Integer.parseInt(parts[3]));
        pdto.setMood(Integer.parseInt(parts[4]));

        UserDTO udto = makeUserDTOInstance(parts);

        pdto.setOwner(udto);
        return pdto;
    }
    catch (Exception e){
        throw new IllegalArgumentException();
    }
}
}

我会饶你UserEditor，因为它与PetEditor非常相似。最后，初始化程序绑定自定义编辑器＆amp;模型类。

VirtualPetDTOInitializer.java

package com.virtualpet.dtoeditors;

import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.support.WebBindingInitializer;
import org.springframework.web.context.request.WebRequest;

import com.virtualpet.virtualpet_dtos.NourishPetDTO;
import com.virtualpet.virtualpet_dtos.PetDTO;
import com.virtualpet.virtualpet_dtos.UserDTO;

public class VirtualPetDTOInitializer implements WebBindingInitializer {

public void initBinder(WebDataBinder binder, WebRequest arg1) {
    // TODO Auto-generated method stub
        binder.registerCustomEditor(UserDTO.class, new UserEditor( ));
        binder.registerCustomEditor(PetDTO.class, new PetEditor( ));
        binder.registerCustomEditor(NourishPetDTO.class, new NourishPetEditor());
}
}

此类在dispatcher-servlet.xml中定义属性值：

<?xml version="1.0" encoding="UTF-8"?>
<beans ...>
<bean id="userDao"
    class="com.virtualpet.virtualpet_daos.UserDAO"/>
<bean id="petDao"
    class="com.virtualpet.virtualpet_daos.PetDAO" />
<bean    class="org.springframwork.web.servlet.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="webBindingInitializer">
        <bean class="com.virtualpet.dtoeditors.VirtualPetDTOInitializer"/>
    </property>
</bean>
</beans>

作为Spring MVC的新手，我必须告诉你，这个错误是我在实现这些类之前得到的。所以，看起来它们不是一个因素，然而，它们的实现是我能找到的一切，在POST之后，模型属性返回null。有人可以帮忙吗？提前致谢。

Answer 1

您需要执行以下操作之一：

将npdto的值存储在隐藏表单字段
在会话中存储npdto
从帖子处理程序

npdto

您可能需要＃2，在这种情况下，在控制器顶部添加@SessionAttributes("npdto")。

您还应该在帖子处理程序中添加SessionStatus参数，并在您不再需要时调用sessionStatus.complete()来清除会话中的项目。

请参阅Spring MVC: Validation, Post-Redirect-Get, Partial Updates, Optimistic Concurrency, Field Security以获取参考答案。

SpringMVC模型属性在帖子

1 个答案: