input text in datatable row expansion returning null value primefaces

Question

I'm showing my database's data in datatable. In the row expansion, I'm setting some values and saving them to the database. I have an input text in row expansion, when I submit the the form the input text's value returning null in my backing bean.

<h:form id="form_2" enctype="multipart/form-data">
                        <p:panel>
                             <p:dataTable var="questions" value="#{EVMView.loadQuestions(EVMView.strSO)}" id="mydatatable2" rowExpandMode="single" editable="true"> 
                             <p:ajax event="rowToggle" rendered="answerText" update="answertype_menu" listener="#{EVMView.onRowToggle(questions.question_ID)}"/>
                                <p:column style="width:2rem">
                                    <p:rowToggler/>
                                </p:column>
                                <p:column headerText="Question">
                                    <h:outputText value="#{questions.questions}"/>
                                </p:column>
                                <p:rowExpansion>
                                    <p:panelGrid columns="2" id="panelmain">
                                    <p:outputLabel for="answertype_menu" value="Answer Type : "/>
                                    <p:selectOneMenu id="answertype_menu" filter="true" filterMatchMode="contains" value="#{EVMView.selectedOption}" required="true" requiredMessage="Select Sales-Order" height="333">
                                        <f:selectItem itemLabel="Select One" itemValue="" noSelectionOption="true"/>
                                        <f:selectItems value="#{EVMView.options(EVMView.selectedModule)}" var="values" itemLabel="#{values.evmOption}" itemValue="#{values.evmOption}"/>
                                        <p:ajax event="change" update="answerText" listener="#{EVMView.getAnswers}" rendered="answerText"/>
                                    </p:selectOneMenu>
                                    <p:outputLabel for="answerText" value="Answer:"  />
                                    <p:inputText id="answerText" value="#{EVMView.answer}" style="width:400px;" readonly="#{EVMView.readOnlyText}"/>
                                    
                                
                                        
                                            <p:outputLabel for="param1" value="#{EVMView.param1Name}" rendered="#{EVMView.visibleParam1}"/>
                                            <p:inputText id="param1" value="#{EVMView.param1}" rendered="#{EVMView.visibleParam1}"/>
                                        
                                        
                                            <p:outputLabel for="param2" value="#{EVMView.param2Name}" rendered="#{EVMView.visibleParam2}"/>
                                            <p:inputText id="param2" value="#{EVMView.param2}" rendered="#{EVMView.visibleParam2}"/>
                                        
                                        
                                            <p:outputLabel for="param3" value="#{EVMView.param3Name}" rendered="#{EVMView.visibleParam3}"/>
                                            <p:inputText id="param3" value="#{EVMView.param3}" rendered="#{EVMView.visibleParam3}"/>
                                        
                                
                                    
                                    
                                            
                                                <p:fileUpload listener="#{fileUploadView.handleFileUpload}" mode="advanced" dragDropSupport="false"
                                                multiple="true" sizeLimit="1000000" fileLimit="3"
                                                allowTypes="/(\.|\/)(gif|jpe?g|png)$/"/>
                                            
                                    
                                    <p:commandButton value="Save EVM Record" action="#{EVMView.saveRecord}" process="@this" update="growl"/>
                                    </p:panelGrid>
                                </p:rowExpansion>
                             </p:dataTable>
                </p:panel>
            </h:form>

A part of my backing bean

@ManagedBean(name="EVMView")
@ViewScoped
public class EVMView {
    @EJB
    private PublicService publicService;
    @EJB
    private EVMService evmService;
    
    private EVMQuestions evmQuestions=new EVMQuestions();
    
    @ManagedProperty(value = "#{loginBean}")
    LoginBean loginBean;
    
    private String strSO;
    private List<SalesOrder> salesOrders;
    private List<String> allModules;
    private List<String> allHeaders;
    private List<EVMQuestions> allQuestions;
    private String selectedOption;
    private List<EVMOptions> optionList;
    private String answer;
    private String selectedModule;
    private String receivedAnswer;
    private int questionID;
    private boolean readOnlyText=true;
    private String param1Name;
    private boolean visibleParam1=false;
    private String param1;
    private String param2Name;
    private String param2;
    private boolean visibleParam2=false;
    private String param3Name;
    private String param3;
    private boolean visibleParam3=false;
    private String mySessionUsername;
    private String mySessionFTEC;
    private String savedDate;
    private EVMResponses evmResponses;
    private EVMParameters evmParameters;
    private String engineType;
    private String selectedHeader;
    

    public String getParam3Name() {
        return param3Name;
    }
    public void setParam3Name(String param3Name) {
        this.param3Name = param3Name;
    }
    public String getParam3() {
        return param3;
    }
    public void setParam3(String param3) {
        this.param3 = param3;
    }
    public boolean isVisibleParam3() {
        return visibleParam3;
    }
    public void setVisibleParam3(boolean visibleParam3) {
        this.visibleParam3 = visibleParam3;
    }
    public boolean isVisibleParam2() {
        return visibleParam2;
    }
    public void setVisibleParam2(boolean visibleParam2) {
        this.visibleParam2 = visibleParam2;
    }
    public String getParam2Name() {
        return param2Name;
    }
    public void setParam2Name(String param2Name) {
        this.param2Name = param2Name;
    }
    public String getParam2() {
        return param2;
    }
    public void setParam2(String param2) {
        this.param2 = param2;
    }
    public String getParam1Name() {
        return param1Name;
    }
    public void setParam1Name(String param1Name) {
        this.param1Name = param1Name;
    }
    public boolean isVisibleParam1() {
        return visibleParam1;
    }
    public void setVisibleParam1(boolean visibleParam1) {
        this.visibleParam1 = visibleParam1;
    }
    public String getParam1() {
        return param1;
    }
    public void setParam1(String param1) {
        this.param1 = param1;
    }
    public boolean isReadOnlyText() {
        return readOnlyText;
    }
    public void setReadOnlyText(boolean readOnlyText) {
        this.readOnlyText = readOnlyText;
    }
    public int getQuestionID() {
        return questionID;
    }
    public void setQuestionID(int questionID) {
        this.questionID = questionID;
    }
    public String getReceivedAnswer() {
        return receivedAnswer;
    }
    public void setReceivedAnswer(String receivedAnswer) {
        this.receivedAnswer = receivedAnswer;
    }
    public List<String> getAllHeaders() {
        return allHeaders;
    }
    public void setAllHeaders(List<String> allHeaders) {
        this.allHeaders = allHeaders;
    }
    public String getSelectedModule() {
        return selectedModule;
    }
    public void setSelectedModule(String selectedModule) {
        this.selectedModule = selectedModule;
    }
    public String getAnswer() {
        return answer;
    }
    public void setAnswer(String answer) {
        this.answer = answer;
    }
public void saveRecord()
{
    System.out.println(this.param1);
}

I couldn't understand why I'm getting null.