Spring 異常處理實例

下麵的例子說明了如何使用Spring MVC的範籌，它可以處理它的內部控製器提出了一個或多個例外編寫一個簡單的基於Web的應用程序。要開始使用它，讓我們使用Eclipse IDE到位，並按照以下步驟使用Spring Web框架開發動態表單的Web應用程序：

步驟	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文件的內容：

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文件的內容：

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文件的內容。在這裡，需要使用@ExceptionHandler標注一個服務方法，可以指定要處理的一個或多個異常。如果要指定一個以上的異常，那麼可以使用逗號分隔值。

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 的內容

<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>

下麵是另一個Spring Web配置文件 HelloWeb-servlet.xml 的內容

<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>

在這裡，指定ExceptionPage在SpringException發生異常的視圖，如果有任何其他類型的異常，然後一個通用視圖的錯誤會發生。

以下是Spring視圖文件student.jsp的內容：

<%@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視圖文件error.jsp的內容：

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

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

</body>
</html>;

以下是Spring視圖文件ExceptionPage.jsp 內容。在這裡將通過${exception}訪問異常實例。

<%@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 視圖文件result.jsp的內容：

<%@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>

最後，下麵是Spring和其他庫包含在Web應用程序的列表。隻需將這些文件拖放它們到WebContent/ WEB-INF/ lib文件夾中。

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

創建源代碼和配置文件完成後，導出應用程序。右鍵單擊應用程序和使用Export> WAR文件選項並保存HelloWeb.war文件到Tomcat的webapps文件夾中。

現在啟動Tomcat服務器，並確保您能夠訪問來自的webapps文件夾中，使用標準的瀏覽器。現在嘗試訪問該URL http://localhost:8080/HelloWeb/student。如果Spring Web應用程序一切正常用，應該看到下麵的結果：

進入如上圖所示的值，然後單擊提交按鈕。如果您的Spring Web應用程序一切順利，應該看到以下結果：