javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Ar

于 2019-10-10 17:04:03 发布
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分类专栏： 前端问题 文章标签： ${a.username}获取不到值的问题  javax.el.PropertyNotFoundExcep
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当在JSP页面中使用EL表达式${a.username}时，出现javax.el.PropertyNotFoundException。问题在于username属性不在Article类中，而是在User类中。正确的访问方式是通过${a.getUser().getUsername()}。此问题涉及到Article类的结构和getter方法的使用。

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my：${a.username}获取不到值的问题

简略错误信息：

message javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article

root cause

javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article

文章最后面放全部错误提示！！！

前端视图中的 EL表达式获取不到相应的值：username！！！

错误写法：
${a.username}
正确写法：
<span>${a.getUser().getUsername() }</span>

总结：
使用<c:forEach var="a" items="${articles}">来调用List<Article> articles中的数据
而articles中的数据联合了 user pojo中的数据，故使用${a.username}是无法获取articles中的username 的

原因：因为username是属于user类的，虽然article联合了user，但无法直接获取，要从user中获取。
用getter方法 获取user，再用getter方法获取username。


-----------------------------------------------------！！！--------------------------------------------------------------------------------
其他相关信息：
1.Article类：

public class Article implements Comparable,Serializable{

    private int article_id;
    private int user_id;
    private String title;            
    private String time;
    private int star;
    private int comment;
    private int visit;
    private String content;
    Tag tag;    
    User user;
    Sort sort;
    
    public Article() {}
    public Tag getTag() {
        return tag;
    }

    public User getUser() {
        return user;
    }

    public Sort getSort() {
        return sort;
    }

    public int getArticle_id() {
        return article_id;
    }

    public void setArticle_id(int article_id) {
        this.article_id = article_id;
    }

    public int getUser_id() {
        return user_id;
    }

    public void setUser_id(int user_id) {
        this.user_id = user_id;
    }

    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    
    public int getStar() {
        return star;
    }
    public void setStar(int star) {
        this.star = star;
    }
    public int getComment() {
        return comment;
    }
    public void setComment(int comment) {
        this.comment = comment;
    }
    public int getVisit() {
        return visit;
    }
    public void setVisit(int visit) {
        this.visit = visit;
    }
    public String getContent() {
        return content;
    }
    public void setContent(String content) {
        this.content = content;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    @Override
    public int compareTo(Object o) {
        if (o instanceof Article) {
            Article article = (Article) o;

            Date this_date = null;
            Date other_date = null;
            try {
                this_date = DateUtils.getDate(this.time);
                other_date = DateUtils.getDate(article.getTime());
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            return -this_date.compareTo(other_date);
        }
        return 0;
    }

    @Override
    public String toString() {
        return "Article [article_id=" + article_id + ", user_id=" + user_id + ", title=" + title + ", time=" + time
                + ", star=" + star + ", comment=" + comment + ", visit=" + visit + ", content=" + content + ", tag="
                + tag + ", user=" + user + ", sort=" + sort + "]";
    }    

}

 

2.mapper层中Article.xml
<select id="getUserArticle" parameterType="Integer" resultMap="getUserArticleResultMap">
        select a.article_id,a.title,a.time,u.username from t_article as a
        join t_user as u on u.user_id = a.user_id
        where u.user_id=#{user_id}
</select>

<resultMap type="Article" id="getUserArticleResultMap">
        <result property="article_id" column="article_id"/>
        <result property="title" column="title"/>
        <result property="time" column="time"/>
        <association property="user" javaType="pers.wsf.multiBlog.pojo.User">
            <result property="username" column="username"/>
        </association>
</resultMap>

------------------------------------------------------！！！-----------------------------------------------------------------------------

错误提示！！！

HTTP Status 500 - javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article

type Exception report

message javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:405)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:349)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
	org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
	org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1244)
	org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

root cause

javax.el.PropertyNotFoundException: Property 'username' not found on type pers.wsf.multiBlog.pojo.Article
	javax.el.BeanELResolver$BeanProperties.get(BeanELResolver.java:245)
	javax.el.BeanELResolver$BeanProperties.access$300(BeanELResolver.java:222)
	javax.el.BeanELResolver.property(BeanELResolver.java:332)
	javax.el.BeanELResolver.getValue(BeanELResolver.java:95)
	org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
	org.apache.el.parser.AstValue.getValue(AstValue.java:167)
	org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:187)
	org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:956)
	org.apache.jsp.page.userManageArticle_jsp._jspx_meth_c_005fforEach_005f0(userManageArticle_jsp.java:205)
	org.apache.jsp.page.userManageArticle_jsp._jspService(userManageArticle_jsp.java:134)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:405)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:349)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
	org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
	org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1244)
	org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
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