Spring - 异常处理示例

以下示例展示了如何使用Spring MVC框架编写一个简单的基于Web的应用程序，该应用程序可以处理其控制器内部引发的一个或多个异常。首先，让我们准备好一个可用的Eclipse IDE，并采取以下步骤使用Spring Web框架开发一个基于动态表单的Web应用程序：

以下是Student.java文件的内容

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;
   }
}

以下是SpringException.java文件的内容

package com.tutorialspoint;

public class SpringException extends RuntimeException{
   private String exceptionMsg;
   
   public SpringException(String exceptionMsg) {
      this.exceptionMsg = exceptionMsg;
   }
   public String getExceptionMsg(){
      return this.exceptionMsg;
   }
   public void setExceptionMsg(String exceptionMsg) {
      this.exceptionMsg = exceptionMsg;
   }
}

以下是StudentController.java文件的内容。在这里，您需要使用@ExceptionHandler注释服务方法，您可以在其中指定要处理的一个或多个异常。如果指定多个异常，则可以使用逗号分隔的值。

package com.tutorialspoint;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
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;
import org.springframework.ui.ModelMap;

@Controller
public class StudentController {
   @RequestMapping(value = "/student", method = RequestMethod.GET)
   public ModelAndView student() {
      return new ModelAndView("student", "command", new Student());
   }
   @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
   @ExceptionHandler({SpringException.class})
   public String addStudent( @ModelAttribute("HelloWeb")Student student, 
      ModelMap model) {
      
      if(student.getName().length() < 5 ){
         throw new SpringException("Given name is too short");
      } else {
         model.addAttribute("name", student.getName());
      }
      
      if( student.getAge() < 10 ){
         throw new SpringException("Given age is too low");
      } else {
         model.addAttribute("age", student.getAge());
      }
      model.addAttribute("id", student.getId());
      return "result";
   }
}

以下是Spring Web配置文件web.xml的内容

<web-app id = "WebApp_ID" version = "2.4"
   xmlns = "http://java.sun.com/xml/ns/j2ee" 
   xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation = "http://java.sun.com/xml/ns/j2ee 
   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
   <display-name>Spring Exception Handling</display-name>
 
   <servlet>
      <servlet-name>HelloWeb</servlet-name>
      <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <load-on-startup>1</load-on-startup>
   </servlet>
   
   <servlet-mapping>
      <servlet-name>HelloWeb</servlet-name>
      <url-pattern>/</url-pattern>
   </servlet-mapping>
  
</web-app>

以下是另一个Spring Web配置文件HelloWeb-servlet.xml的内容

<beans xmlns = "http://www.springframework.org/schema/beans"
   xmlns:context = "http://www.springframework.org/schema/context"
   axmlns: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 class = "org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
      <property name = "exceptionMappings">
         <props>
            <prop key = "com.tutorialspoint.SpringException">
               ExceptionPage
            </prop>
         </props>
      </property>
      <property name = "defaultErrorView" value = "error"/>
   </bean>

</beans>

在这里，您指定了ExceptionPage作为发生SpringException时的异常视图，如果存在任何其他类型的异常，则将使用通用视图error。

以下是Spring视图文件student.jsp的内容

<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
   <head>
      <title>Spring MVC Exception Handling</title>
   </head>

   <body>
      <h2>Student Information</h2>
      <form:form method = "POST" action = "/HelloWeb/addStudent">
         <table>
            <tr>
               <td><form:label path = "name">Name</form:label></td>
               <td><form:input path = "name" /></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>

以下是Spring视图文件error.jsp的内容

<html>
   <head>
      <title>Spring Error Page</title>
   </head>

   <body>
      <p>An error occured, please contact webmaster.</p>
   </body>
</html>

以下是Spring视图文件ExceptionPage.jsp的内容。在这里，您将通过${exception}访问异常实例。

<%@taglib uri = "http://www.springframework.org/tags/form" prefix = "form"%>
<html>
   <head>
      <title>Spring MVC Exception Handling</title>
   </head>

   <body>
      <h2>Spring MVC Exception Handling</h2>
      <h3>${exception.exceptionMsg}</h3>
   </body>
</html>

以下是Spring视图文件result.jsp的内容

<%@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>

最后，以下是需要包含在您的Web应用程序中的Spring和其他库的列表。您只需将这些文件拖放到WebContent/WEB-INF/lib文件夹中。

• commons-logging-x.y.z.jar
• org.springframework.asm-x.y.z.jar
• org.springframework.beans-x.y.z.jar
• org.springframework.context-x.y.z.jar
• org.springframework.core-x.y.z.jar
• org.springframework.expression-x.y.z.jar
• org.springframework.web.servlet-x.y.z.jar
• org.springframework.web-x.y.z.jar
• spring-web.jar

创建完源文件和配置文件后，导出您的应用程序。右键单击您的应用程序，并使用导出 > WAR文件选项，并将您的HelloWeb.war文件保存到Tomcat的webapps文件夹中。

现在启动您的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。现在尝试访问URL https://127.0.0.1:8080/HelloWeb/student。如果您的Spring Web应用程序一切正常，您应该会看到以下结果。

输入如上所示的值，然后单击提交按钮。如果您的Spring Web应用程序一切正常，您应该会看到以下结果。