Errors

以下示例说明如何使用Spring Web MVC Framework在表单中使用错误处理和验证器。 首先，让我们使用一个可用的Eclipse IDE，并考虑使用Spring Web Framework开发基于动态表单的Web应用程序的以下步骤。

Student.java

package cn.xnip;
public class Student {
   private Integer age;
   private String name;
   private Integer id;
   public void setAge(Integer age) {
      this.age = age;
   }
   public Integer getAge() {
      return age;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getName() {
      return name;
   }
   public void setId(Integer id) {
      this.id = id;
   }
   public Integer getId() {
      return id;
   }
}

StudentValidator.java

package cn.xnip;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
public class StudentValidator implements Validator {
   @Override
   public boolean supports(Class<?> clazz) {
      return Student.class.isAssignableFrom(clazz);
   }
   @Override
   public void validate(Object target, Errors errors) {		
      ValidationUtils.rejectIfEmptyOrWhitespace(errors, 
         "name", "required.name","Field name is required.");
   }
}

StudentController.java

package cn.xnip;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.validation.BindingResult;
import org.springframework.validation.Validator;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class StudentController {
   @Autowired
   @Qualifier("studentValidator")
   private Validator validator;
   @InitBinder
   private void initBinder(WebDataBinder binder) {
      binder.setValidator(validator);
   }
   @RequestMapping(value = "/addStudent", method = RequestMethod.GET)
   public ModelAndView student() {
      return new ModelAndView("addStudent", "command", new Student());
   }
   @ModelAttribute("student")
   public Student createStudentModel() {	
      return new Student();
   }
   @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
   public String addStudent(@ModelAttribute("student") @Validated Student student, 
      BindingResult bindingResult, Model model) {
      if (bindingResult.hasErrors()) {
         return "addStudent";
      }
      model.addAttribute("name", student.getName());
      model.addAttribute("age", student.getAge());
      model.addAttribute("id", student.getId());
      return "result";
   }
}

HelloWeb-servlet.xml

<beans xmlns = "http://www.springframework.org/schema/beans"
   xmlns:context = "http://www.springframework.org/schema/context"
   xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation = "
   http://www.springframework.org/schema/beans     
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/context 
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
   <context:component-scan base-package = "cn.xnip" />
   <bean class = "org.springframework.web.servlet.view.InternalResourceViewResolver">
      <property name = "prefix" value = "/WEB-INF/jsp/" />
      <property name = "suffix" value = ".jsp" />
   </bean>
   <bean id = "studentValidator" class = "cn.xnip.StudentValidator" />
</beans>

这里，对于第一个服务方法student() ，我们在ModelAndView对象中传递了名为“command”的空白Studentobject，因为如果使用“form:form”标签，spring框架需要一个名为“command”的对象在您的JSP文件中。 因此，当调用student（）方法时，它会返回addStudent.jsp视图。

将针对HelloWeb/addStudent URL上的POST方法调用第二个服务方法addStudent() 。 您将根据提交的信息准备模型对象。 最后，将从service方法返回“result”视图，这将导致呈现result.jsp。 如果使用验证器生成错误，则返回相同的视图“addStudent”，Spring会自动从视图中的BindingResult注入错误消息。

addStudent.jsp

<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
   <head>
      <title>Spring MVC Form Handling</title>
   </head>
   <style>
      .error {
         color: #ff0000;
      }
      .errorblock {
         color: #000;
         background-color: #ffEEEE;
         border: 3px solid #ff0000;
         padding: 8px;
         margin: 16px;
      }
   </style>
   <body>
      <h2>Student Information</h2>
      <form:form method = "POST" action = "/HelloWeb/addStudent" commandName = "student">
      <form:errors path = "*" cssClass = "errorblock" element = "div" />
         <table>
            <tr>
               <td><form:label path = "name">Name</form:label></td>
               <td><form:input path = "name" /></td>
               <td><form:errors path = "name" cssClass = "error" /></td>
            </tr>
            <tr>
               <td><form:label path = "age">Age</form:label></td>
               <td><form:input path = "age" /></td>
            </tr>
            <tr>
               <td><form:label path = "id">id</form:label></td>
               <td><form:input path = "id" /></td>
            </tr>
            <tr>
               <td colspan = "2">
               <input type = "submit" value = "Submit"/>
               </td>
            </tr>
         </table>  
      </form:form>
   </body>
</html>

这里我们使用带有path =“*”的《form:errors /》标签来呈现错误消息。 例如

<form:errors path = "*" cssClass = "errorblock" element = "div" />

它将呈现所有输入验证的错误消息。

我们使用带有path =“name”的《form:errors /》标签来为name字段呈现错误消息。 例如

<form:errors path = "name" cssClass = "error" />

它将为名称字段验证呈现错误消息。

result.jsp

<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
   <head>
      <title>Spring MVC Form Handling</title>
   </head>
   <body>
      <h2>Submitted Student Information</h2>
      <table>
         <tr>
            <td>Name</td>
            <td>${name}</td>
         </tr>
         <tr>
            <td>Age</td>
            <td>${age}</td>
         </tr>
         <tr>
           <td>ID</td>
           <td>${id}</td>
         </tr>
      </table>  
   </body>
</html>

完成创建源文件和配置文件后，导出应用程序。 右键单击您的应用程序，使用Export → WAR File选项并将HelloWeb.war文件保存在Tomcat的webapps文件夹中。

现在，启动Tomcat服务器并确保您可以使用标准浏览器从webapps文件夹访问其他网页。 尝试一个URL - http://localhost:8080/HelloWeb/addStudent ，如果Spring Web Application的一切正常，我们将看到以下屏幕。

提交所需信息后，单击提交按钮以提交表单。 如果Spring Web Application的一切正常，您应该看到以下屏幕。