Springmvc 简明教程

Spring MVC - Error Handling Example

以下示例展示了如何在表单中使用Spring Web MVC框架中的错误处理和验证器。首先，让我们使用Eclipse IDE并按照以下步骤使用Spring Web框架开发一个基于动态表单的Web应用程序。

The following example shows how to use Error Handling and Validators in forms using the Spring Web MVC Framework. To start with, let us have a working Eclipse IDE in place and consider the following steps to develop a Dynamic Form based Web Application using the Spring Web Framework.

Step	Description
1	Create a project with a name HelloWeb under a package com.tutorialspoint as explained in the Spring MVC - Hello World chapter.
2	Create Java classes Student, StudentController and StudentValidator under the com.tutorialspoint package.
3	Create view files addStudent.jsp, result.jsp under the jsp sub-folder.
4	The final step is to create the content of the source and configuration files and export the application as explained below.

Student.java

package com.tutorialspoint;

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 com.tutorialspoint;

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 com.tutorialspoint;

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 = "com.tutorialspoint" />

   <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 = "com.tutorialspoint.StudentValidator" />
</beans>

在这里，对于第一个服务方法 student() ，我们在ModelAndView对象中传递了一个空白Studentobject，名称为“command”，因为如果您在JSP文件中使用<form:form>标记，Spring框架将期待一个名为“command”的对象。因此，当调用student()方法时，它将返回 addStudent.jsp 视图。

Here, for the first service method student(), we have passed a blank Studentobject in the ModelAndView object with name "command", because the spring framework expects an object with name "command", if you are using <form:form> tags in your JSP file. So, when student() method is called, it returns addStudent.jsp view.

第二个服务方法 addStudent() 将在 HelloWeb/addStudent URL上的POST方法中被调用。您将根据提交的信息准备您的模型对象。最后，将从服务方法中返回“result”视图，这将导致渲染result.jsp。如果使用验证器生成了错误，那么将返回相同的“addStudent”视图，Spring将自动在视图中从 BindingResult 注入错误消息。

The second service method addStudent() will be called against a POST method on the HelloWeb/addStudent URL. You will prepare your model object based on the submitted information. Finally, a "result" view will be returned from the service method, which will result in rendering the result.jsp. In case there are errors generated using validator then same view "addStudent" is returned, Spring automatically injects error messages from BindingResult in view.

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>

在这里，我们使用 <form:errors /> 标签和path="*"来呈现错误消息。例如

Here we are using <form:errors /> tag with path="*" to render error messages. For example

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

它将呈现所有输入验证的错误消息。

It will render the error messages for all input validations.

我们使用 <form:errors /> 标签和path="name"来呈现name字段的错误消息。例如

We are using <form:errors /> tag with path="name" to render error message for name field. For example

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

它将呈现name字段验证的错误消息。

It will render error messages for the name field validations.

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>

一旦创建完源文件和配置文件，导出您的应用程序。右键单击应用程序，使用 Export → WAR File 选项，并将 HelloWeb.war 文件保存到 Tomcat 的 webapps 文件夹中。

Once you are done with creating source and configuration files, export your application. Right click on your application, use Export → WAR File option and save the HelloWeb.war file in Tomcat’s webapps folder.

现在，启动 Tomcat 服务器并确保能够使用标准浏览器访问 webapps 文件夹中的其他网页。尝试以下 URL - http://localhost:8080/HelloWeb/addStudent 如果 Spring Web 应用程序一切正常，我们会看到以下屏幕。

Now, start your Tomcat server and make sure you are able to access other webpages from webapps folder using a standard browser. Try a URL − http://localhost:8080/HelloWeb/addStudent and we will see the following screen, if everything is fine with the Spring Web Application.

提交所需信息后，单击提交按钮提交表单。如果 Spring Web 应用程序一切正常，您应该看到以下屏幕。

After submitting the required information, click on the submit button to submit the form. You should see the following screen, if everything is fine with the Spring Web Application.