弹簧编辑表格不保留日期字段

Question

我正在尝试使用spring form执行更新操作。我的实体中很少有字段没有绑定在弹簧形式上（日期字段：createdDate，modifiedDate）。但是当我提交表单时，控制器上的日期字段变为空。我尝试过使用form：hidden field但是在提交表单时也没有保留datefields。请帮忙     这是我的实体

@Entity
@Table(name = "PORTAL_SUPPLIER")
public class PortalSupplier extends AbstractEntity implements Serializable {
    /**
     * 
     */
    private static final long serialVersionUID = 2187090408756348981L;

    @Id
    @Column(name = "SUPP_ID")
    @TableGenerator(table = "PORTAL_TABLE_GENERATOR", name = "TABLE_SEQ_GENERATOR", pkColumnValue = "SUPP_ID",allocationSize = 1, initialValue = 1)
    @GeneratedValue(strategy = GenerationType.TABLE, generator = "TABLE_SEQ_GENERATOR")
    private int supplierId;

    @Column(name = "TIN_NUM", nullable = true, length = 100)
    private String tinNumber;

    @Column(name = "SUPP_NAME", nullable = false, length = 200)
    private String supplierName;

    @Column(name = "SUPP_ADDRESS", nullable = true, length = 500)
    private String supplierAddress;

    @Column(name = "SUPP_EMAIL_ID", nullable = true, length = 100)
    private String supplierEmailId;

    @Column(name = "SUPP_PHONE_NUM", nullable = true, length = 20)
    private String supplierPhoneNumber;

    @Column(name = "SUPP_MOBILE_NUM", nullable = true, length = 20)
    private String supplierMobileNumber;

    @Column(name = "SUPP_ACTIVE_FLAG", nullable = false, length = 1)
    private String supplierActive;

    @Column(name = "MONTH", nullable = false, length = 2)
    private int month;

    @Column(name = "YEAR", nullable = false, length = 4)
    private int year;

    /**
     * @return the supplierId
     */
    public int getSupplierId() {
        return supplierId;
    }

    /**
     * @param supplierId the supplierId to set
     */
    public void setSupplierId(int supplierId) {
        this.supplierId = supplierId;
    }

    /**
     * @return the tinNumber
     */
    public String getTinNumber() {
        return tinNumber;
    }

    /**
     * @param tinNumber the tinNumber to set
     */
    public void setTinNumber(String tinNumber) {
        this.tinNumber = tinNumber;
    }

    /**
     * @return the supplierName
     */
    public String getSupplierName() {
        return supplierName;
    }

    /**
     * @param supplierName the supplierName to set
     */
    public void setSupplierName(String supplierName) {
        this.supplierName = supplierName;
    }

    /**
     * @return the supplierAddress
     */
    public String getSupplierAddress() {
        return supplierAddress;
    }

    /**
     * @param supplierAddress the supplierAddress to set
     */
    public void setSupplierAddress(String supplierAddress) {
        this.supplierAddress = supplierAddress;
    }

    /**
     * @return the supplierEmailId
     */
    public String getSupplierEmailId() {
        return supplierEmailId;
    }

    /**
     * @param supplierEmailId the supplierEmailId to set
     */
    public void setSupplierEmailId(String supplierEmailId) {
        this.supplierEmailId = supplierEmailId;
    }

    /**
     * @return the supplierPhoneNumber
     */
    public String getSupplierPhoneNumber() {
        return supplierPhoneNumber;
    }

    /**
     * @param supplierPhoneNumber the supplierPhoneNumber to set
     */
    public void setSupplierPhoneNumber(String supplierPhoneNumber) {
        this.supplierPhoneNumber = supplierPhoneNumber;
    }

    /**
     * @return the supplierMobileNumber
     */
    public String getSupplierMobileNumber() {
        return supplierMobileNumber;
    }

    /**
     * @param supplierMobileNumber the supplierMobileNumber to set
     */
    public void setSupplierMobileNumber(String supplierMobileNumber) {
        this.supplierMobileNumber = supplierMobileNumber;
    }

    /**
     * @return the supplierActive
     */
    public String getSupplierActive() {
        return supplierActive;
    }

    /**
     * @param supplierActive the supplierActive to set
     */
    public void setSupplierActive(String supplierActive) {
        this.supplierActive = supplierActive;
    }

    /**
     * @return the month
     */
    public int getMonth() {
        return month;
    }

    /**
     * @param month the month to set
     */
    public void setMonth(int month) {
        this.month = month;
    }

    /**
     * @return the year
     */
    public int getYear() {
        return year;
    }

    /**
     * @param year the year to set
     */
    public void setYear(int year) {
        this.year = year;
    }

}

这是我的abstractbaseentity

@MappedSuperclass
public abstract class AbstractEntity  {

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "DATE_CREATED", nullable = false)
    private Date dateCreated;

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "DATE_MODIFIED", nullable =false)
    private Date dateModified;

    @PrePersist
    @PreUpdate
    private void updateDate(){
        dateModified = new Date();
    }

    /**
     * @return the dateCreated
     */
    public Date getDateCreated() {
        return dateCreated;
    }

    /**
     * @param dateCreated the dateCreated to set
     */
    public void setDateCreated(Date dateCreated) {
        this.dateCreated = dateCreated;
    }

    /**
     * @return the dateModified
     */
    public Date getDateModified() {
        return dateModified;
    }

    /**
     * @param dateModified the dateModified to set
     */
    public void setDateModified(Date dateModified) {
        this.dateModified = dateModified;
    }
}

这是我的编辑表格

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Add Supplier</title>
</head>
<body>
    <form:form method="post" modelAttribute="supplier" id="addSupplierForm">
        <table border="0">
            <tr>
                <td><form:label path="tinNumber">TIN NUMBER</form:label></td>
                <td><form:input path="tinNumber" /></td>
            </tr>
            <tr>
                <td><form:label path="supplierName">SUPPLIER NAME</form:label></td>
                <td><form:input path="supplierName" /></td>
            </tr>
            <tr>
                <td><form:label path="supplierAddress">SUPPLIER ADDRESS</form:label></td>
                <td><form:input path="supplierAddress" /></td>
            </tr>
            <tr>
                <td><form:label path="supplierEmailId">SUPPLIER EMAIL ID</form:label></td>
                <td><form:input path="supplierEmailId" /></td>
            </tr>
            <tr>
                <td><form:label path="supplierPhoneNumber">SUPPLIER PHONE NUMBER</form:label></td>
                <td><form:input path="supplierPhoneNumber" /></td>
            </tr>

            <tr>
                <td><form:label path="supplierMobileNumber">SUPPLIER MOBILE NUMBER</form:label></td>
                <td><form:input path="supplierMobileNumber" /></td>
            </tr>
            <tr>
                <td><form:label path="month">MONTH</form:label></td>
                <td><form:input path="month" /></td>
            </tr>
            <tr>
                <td><form:label path="year">YEAR</form:label></td>
                <td><form:input path="year" /></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="SUBMIT"></td>
            </tr>
            <tr>
            <td><form:hidden path="supplierActive"/></td>
            <td><form:hidden path="dateCreated"/></td>
            <td><form:hidden path="dateModified"/></td>
            </tr>
        </table>


    </form:form>
</body>
</html>