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JSP中List中的$ {employee.id}抛出java.lang.NumberFormatException:对于输入字符串:“ id”

陶博耘
2023-03-14
问题内容

我有一个JSP页面,当List<Employee>从下方的方法显示时,该页面工作正常<c:forEach>

@RequestMapping(value = { "getAllEmployees", "/" })
public ModelAndView getAllEmployees() {
    // logger.info("Getting the all Employees.");
    List<Employee> employeeList = employeeService.getAllEmployees();
    return new ModelAndView("employeeList", "employeeList", employeeList);
}

List<Employee>从下面的方法显示时,同一JSP会引发异常。

@RequestMapping("searchEmployee")
public ModelAndView searchEmployee(@RequestParam("searchName") String searchName) {
    // logger.info("Searching the Employee. Employee Names: " + searchName);
    List<Employee> employeeList = employeeService.getAllEmployees(searchName);
    System.err.println("Employee count = "+employeeList.size());
    return new ModelAndView("employeeList", "employeeList", employeeList);
}

这是堆栈跟踪:

java.lang.NumberFormatException: For input string: "id"
    java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    java.lang.Integer.parseInt(Integer.java:492)
    java.lang.Integer.parseInt(Integer.java:527)
    javax.el.ArrayELResolver.coerce(ArrayELResolver.java:151)
    javax.el.ArrayELResolver.getValue(ArrayELResolver.java:64)
    org.apache.jasper.el.JasperELResolver.getValue(JasperELResolver.java:110)
    org.apache.el.parser.AstValue.getValue(AstValue.java:169)
    org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:184)
    org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:943)
    org.apache.jsp.WEB_002dINF.pages.employeeList_jsp._jspx_meth_c_005fout_005f0(employeeList_jsp.java:358)
    org.apache.jsp.WEB_002dINF.pages.employeeList_jsp._jspx_meth_c_005fforEach_005f0(employeeList_jsp.java:312)
    org.apache.jsp.WEB_002dINF.pages.employeeList_jsp._jspx_meth_c_005fif_005f1(employeeList_jsp.java:273)
    org.apache.jsp.WEB_002dINF.pages.employeeList_jsp._jspService(employeeList_jsp.java:162)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    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:1228)
    org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    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:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

这是怎么引起的,我该如何解决?


问题答案:

你的getAllEmployees(searchName)方法不会返回List<Employee>,而是返回List<Object[]>。很可能还会有编译器生成的“未经检查的强制转换”警告,你忽略或取消了该警告。

证据是参与javax.el.ArrayELResolver堆栈跟踪。仅在EL表达式的基数为数组类型时才涉及此内容。如果确实有一个Employee而不是Object[],那么你将期望javax.el.BeanELResolver${employee.id}要评估EL表达式的特定堆栈跟踪行中。与${employee}你实际的情况一样,EL会将id属性解释为数组索引,然后尝试将其解析为Integer,但是这样做失败,如你在堆栈跟踪的顶部看到的那样。

要解决此问题,你有两种选择:

修复getAllEmployees(searchName)返回实数 的方法List<Employee>。通常,这是通过Employee直接查询实体而不是单个列/字段来完成的。

更换所有不正确的List<Employee>通过声明List<Object[]>和在EL处理它作为一个对象数组像这样${employee[0]}${employee[1]}



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