用spring和bean列表创建一个表单

Question

I know there are similar questions to mine but I can't make it work. But please bear with me.

Here is my bean

public class FLTQuestionnaireBean
{
    private int myQuestionId;
    private int myQuestionNum;
    private String myQuestion;
    private String myQuestionAnswer;
    private String myQuestionType;
    private String myQuestionModule;
    private String myQuestionStrand;
    private String myQuestionDifficulty;

    // getters and setters here
}

And my wrapper class:

public class QuestionnaireBeanWrapper
{
    private List<FLTQuestionnaireBean> myQuestionnaireBeanList;

    public void add( FLTQuestionnaireBean questionnaireBean )
    {
        myQuestionnaireBeanList.add( questionnaireBean );
    }

        //getter and setter here
}

EDIT: change modelAttribute from ${ wrapper } to "wrapper" Spring form

<form:form id="reading-form" action="../index/FLT_evaluate_reading.do" method="POST" modelAttribute="wrapper">
     <c:forEach items="${ wrapper.questionnaireBeanList }" varStatus="i">
           <form:input path="questionnaireBeanList[${i.index}].questionId" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionNum" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].question" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionAnswer" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionType" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionModule" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionStrand" type="text"/>
           <form:input path="questionnaireBeanList[${i.index}].questionDifficulty" type="text"/>
      </c:forEach>
</form:form>

Controller

@RequestMapping( value = "/index/FLT", method = RequestMethod.GET )
public String indexFLT( @RequestParam( defaultValue = "" )
String message, @RequestParam( defaultValue = "" )
String messageType, ModelMap model )
{
    model.addAttribute( "message", message );
    model.addAttribute( "messageType", messageType );

    QuestionnaireBeanWrapper wrapper = new QuestionnaireBeanWrapper();
    wrapper.add( new FLTQuestionnaireBean() );
    wrapper.add( new FLTQuestionnaireBean() );

    model.addAttribute( "wrapper", wrapper );

    return "als-questionnaire/flt";
}

I'm getting an exception when I run the app. I'm getting the error starting at first <form:input.. heres my stacktrace:

EDIT: Change of stactrace

   java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'com' available as request attribute
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:141)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:154)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.autogenerateId(AbstractDataBoundFormElementTag.java:141)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.resolveId(AbstractDataBoundFormElementTag.java:132)
    at org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:116)
...

Can you tell me what am I doing wrong? I really need help. Thanks in advance.

Answer 1

Check spell of get-er in wrapper class it should be something like this

public List<FLTQuestionnaireBean> getQuestionnaireBeanList{
return myQuestionnaireBeanList
};

Answer 2

Change this

<form:form id="reading-form" action="../index/FLT_evaluate_reading.do" method="POST" modelAttribute="${ wrapper }">

to

<form:form id="reading-form" action="../index/FLT_evaluate_reading.do" method="POST" modelAttribute="wrapper">

The form tag's modelAttribute element needs the name of the model attribute, not the object itself (or rather its toString() result), which you get from ${wrapper} .

The hint was

Neither BindingResult nor plain target object for bean name 'com'

I am sure if you do

wrapper.toString()

and print the result in your controller, you will see something like

com.somepackage.QuestionnaireBeanWrapper

It tries to use that to resolve the model attribute, resolving each token before a . , failing on the first it doesn't find in the Model attributes. In this case, there is nothing called com in the Model attributes, so it complains and fails.