我想將文章存儲在我的表中，我希望自動生成發布日期并將其存儲在數據庫中。publishedDate每當我添加文章時，我的文章表中的列都會顯示 NULL。我想自動插入日期，我該怎么做？我的實體類和 JSP 文件中有以下代碼<%@ page language="java" contentType="text/html; charset=ISO-8859-1"    pageEncoding="ISO-8859-1"%><%@ taglib uri="http://www.springframework.org/tags/form" prefix="form" %><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%@page import="java.util.Date" %><jsp:useBean id="now" class="java.util.Date" /><c:url value="/admin/article/save" var="url"></c:url>            <form:form class="form-horizontal" action="${url}" modelAttribute="article"                method="POST" enctype="multipart/form-data" style="margin-top:5rem;" >                <fieldset>                <form:hidden path="articleViews" value="${article.articleViews}" />                <form:hidden path="publishedDate" id="publishedDate" value="${now}" />                <form:hidden path="articleId" value="${article.articleId}" />import java.io.Serializable;import java.util.Comparator;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Transient;import org.hibernate.annotations.Generated;import org.hibernate.annotations.GenerationTime;import org.springframework.web.multipart.MultipartFile;@Entity@Tablepublic class Article implements Serializable,Comparator<Article>{    /**     *      */    private static final long serialVersionUID = -4756552789390263788L;    @Id    @GeneratedValue(strategy = GenerationType.AUTO)    private Long articleId;    private String articleHeading;    @Column(columnDefinition = "TEXT")    private String articleIntroduction;    @Column(columnDefinition = "TEXT")    private String articleDescription;    @Column(columnDefinition = "TEXT")    private String articleSummary;    @Transient    private MultipartFile aImage;   private String articleCategory;