Question

我有一个JSP页面，可以在List<Employee>中从下面的方法显示<c:forEach>时正常工作。

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

然而，当从下面的方法显示List<Employee>时，同一个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)

这是如何引起的？如何解决？

Answer 1

您的getAllEmployees(searchName)方法不会返回List<Employee>，而是List<Object[]>。很可能还有一个＆＃34;未经检查的演员＆＃34;由您忽略或禁止的编译器生成的警告。

证据是javax.el.ArrayELResolver参与堆栈跟踪。这仅在EL表达式的基础是数组类型时才会涉及。如果你真的有一个Employee而不是Object[]，那么你应该在特定的堆栈跟踪线上预期javax.el.BeanELResolver来评估EL表达式${employee.id} 。由于${employee}在你的情况下实际上是一个数组，EL会将id属性解释为数组索引，然后尝试将其解析为Integer，但是你没能这样做请参阅堆栈跟踪的顶行。

要解决此问题，您有2个选项：

修复getAllEmployees(searchName)方法以返回真实 List<Employee>。通常，这是通过直接查询Employee实体而不是通过单列/字段来完成的。
将所有不正确的List<Employee>声明替换为List<Object[]>，并将其作为对象数组处理，如${employee[0]}，${employee[1]}等。

来自JSP中List的$ {employee.id}抛出java.lang.NumberFormatException：对于输入字符串：＆＃34; id＆＃34;

1 个答案: