Spring 异常处理实例

下面的例子说明了如何使用Spring MVC的范筹，它可以处理它的内部控制器提出了一个或多个例外编写一个简单的基于Web的应用程序。要开始使用它，让我们使用Eclipse IDE到位，并按照以下步骤使用Spring Web框架开发动态表单的Web应用程序：

步骤	描述
1	Create a Dynamic Web Project with a name HelloWeb and create a packagecom.yiibai under the src folder in the created project.
2	Drag and drop below mentioned Spring and other libraries into the folder WebContent/WEB-INF/lib.
3	Create a Java classes Student, StudentController and SpringException under thecom.yiibai package.
4	Create Spring configuration files Web.xml and HelloWeb-servlet.xml under theWebContent/WEB-INF folder.
5	Create a sub-folder with a name jsp under the WebContent/WEB-INF folder. Create a view files student.jsp, result.jsp, error.jsp, and ExceptionPage.jsp under jsp sub-folder.
6	The final step is to create the content of all the source and configuration files and export the application as explained below.

以下是Student.java文件的内容：

package com.yiibai;

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.yiibai;

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，需要使用@ExceptionHandler标注一个服务方法，可以指定要处理的一个或多个异常。如果要指定一个以上的异常，那么可以使用逗号分隔值。

package com.yiibai;

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>

下面是另一个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"
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.yiibai" />

<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.yiibai.SpringException">
            ExceptionPage
         </prop>
      </props>
   </property>
   <property name="defaultErrorView" value="error"/>
</bean>

</beans>

在这里，指定ExceptionPage在SpringException发生异常的视图，如果有任何其他类型的异常，然后一个通用视图的错误会发生。

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 内容。在这里将通过${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，下面是Spring和其他库包含在Web应用程序的列表。只需将这些文件拖放它们到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

创建源代码和配置文件完成后，导出应用程序。右键单击应用程序和使用Export> WAR文件选项并保存HelloWeb.war文件到Tomcat的webapps文件夹中。

现在启动Tomcat服务器，并确保您能够访问来自的webapps文件夹中，使用标准的浏览器。现在尝试访问该URL http://localhost:8080/HelloWeb/student。如果Spring Web应用程序一切正常用，应该看到下面的结果：

进入如上图所示的值，然后单击提交按钮。如果您的Spring Web应用程序一切顺利，应该看到以下结果：