Exception evaluating SpringEL expression: “session.user.name“ (template: “system/index/index“ - lin

夏建木

2023-12-01

报错信息1：

his application has no explicit mapping for /error, so you are seeing this as a fallback.

Tue Jan 19 22:52:21 CST 2021
There was an unexpected error (type=Internal Server Error, status=500).
An error happened during template parsing (template: "class path resource [templates/system/index/index.html]")
org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/system/index/index.html]")
	at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:241)
	at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parseStandalone(AbstractMarkupTemplateParser.java:100)
	at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:666)
	at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1098)
	at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1072)
	at org.thymeleaf.spring5.view.ThymeleafView.renderFragment(ThymeleafView.java:362)
	at org.thymeleaf.spring5.view.ThymeleafView.render(ThymeleafView.java:189)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1394)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1139)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1078)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:961)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:112)

报错信息2：

Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "session.user.name" (template: "system/index/index" - line 31, col 158)
	at org.thymeleaf.spring5.expression.SPELVariableExpressionEvaluator.evaluate(SPELVariableExpressionEvaluator.java:290) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
	at org.thymeleaf.standard.expression.VariableExpression.executeVariableExpression(VariableExpression.java:166) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
	at org.thymeleaf.standard.expression.SimpleExpression.executeSimple(SimpleExpression.java:66) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
	at org.thymeleaf.standard.expression.Expression.execute(Expression.java:109) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]

前端页面使用thymeleaf 获取值

<html xmlns:th="http://www.thymeleaf.org">

<div class="layui-header header">
			<div class="layui-main mag0">
				<a href="#" class="logo">后台系统管理</a>
				<!-- 显示/隐藏菜单 -->
				<a href="javascript:;" class="seraph hideMenu icon-caidan"></a>
			    <!-- 顶部右侧菜单 -->
			    <ul class="layui-nav top_menu">
					<li class="layui-nav-item lockcms" pc>
						<a href="javascript:;"><i class="seraph icon-lock"></i><cite>锁屏</cite></a>
					</li>
					<li class="layui-nav-item" id="userInfo">
						<a href="javascript:;"><img src="/resources/images/login_bg.jpg" class="layui-nav-img userAvatar" width="35" height="35"><cite class="adminName"><span th:text="${session.user?.name}"></span></cite></a>
						<dl class="layui-nav-child">
							<dd><a href="javascript:;" data-url="/resouces/page/user/userInfo.html"><i class="seraph icon-ziliao" data-icon="icon-ziliao"></i><cite>个人资料</cite></a></dd>
							<dd><a href="javascript:;" data-url="/resouces/page/user/changePwd.html"><i class="seraph icon-xiugai" data-icon="icon-xiugai"></i><cite>修改密码</cite></a></dd>
							<dd><a href="javascript:;" class="signOut logout"><i class="seraph icon-tuichu"></i><cite>退出</cite></a></dd>
						</dl>
					</li>
				</ul>
			</div>
		</div>

报错位置：session.user.name

<a href="javascript:;"><img src="/resources/images/login_bg.jpg" class="layui-nav-img userAvatar" width="35" height="35"><cite class="adminName"><span th:text="${session.user.name}"></span></cite></a>

更改后代码：session.user?.name 加个判断，判断user不能为空

<a href="javascript:;"><img src="/resources/images/login_bg.jpg" class="layui-nav-img userAvatar" width="35" height="35"><cite class="adminName"><span th:text="${session.user?.name}"></span></cite></a>

再在后台控制器中再判断user不能为空就可以了

报错原因：不影响使用，刚开始登录可以，一旦session清空，对象name值就获取不到了，所有就空指针了，所以需要判断对象不能为空

Exception evaluating SpringEL expression: “session.user.name“ (template: “system/index/index“ - lin

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