13.4、异常处理——SimpleMappingExceptionResolver

如果希望对所有的异常进行统一的处理，比如当指定的异常发生时，把它映射到要显示的错误的网页中，此时用SimpleMappingExceptionResolver进行解析。DispatcherServlet中没有实现SimpleMappingExceptionResolver的Bean，所有需要在spring的配置文件中进行配置。示例如下：
1、web.xml和spring的配置文件
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">

    <!-- The front controller of this Spring Web application, responsible for handling all application requests -->
    <servlet>
        <servlet-name>springDispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <!-- Map all requests to the DispatcherServlet for handling -->
    <servlet-mapping>
        <servlet-name>springDispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

spring的配置文件springmvc.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">

    <context:component-scan base-package="com.lzj.springmvc"></context:component-scan>
    <!--配置视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <mvc:annotation-driven></mvc:annotation-driven>
</beans>

2、创建请求
在WebContent下面创建index.jsp，内容为：

<a href="springMVC/testSimpleMappingExceptionResolver?i=11">Test SimpleMappingExceptionResolver</a>

3、创建请求控制器
控制器用于截获index.jsp中的请求

@Controller
@RequestMapping("/springMVC")
public class TestSpringMVC {

    @RequestMapping("/testSimpleMappingExceptionResolver")
    public String testSimpleMappingExceptionResolver(){
        String[] values = new String[10];
        //下标越界了
        System.out.println(values[11]);
        return "success";
    }
}

发送index.jsp中的超链接请求，控制器捕获请求后处理控制器逻辑，由于在逻辑中，数组越界，会抛出ArrayIndexOutOfBoundsException异常。
4、处理异常

spring中的配置文件应改为如下
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">

    <context:component-scan base-package="com.lzj.springmvc"></context:component-scan>
    <!--配置视图解析器-->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/views/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

    <mvc:annotation-driven></mvc:annotation-driven>

    <!-- 配置使用SimpleMappingExceptionResolver来映射异常 -->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <!-- 给异常命名一个别名 -->
        <property name="exceptionAttribute" value="ex"></property>
        <property name="exceptionMappings">
            <props>
                <!-- 一定要异常的全类名。 
                表示出现ArrayIndexOutOfBoundsException异常，就跳转到error.jsp视图-->
                <prop key="java.lang.ArrayIndexOutOfBoundsException">error</prop>
            </props>
        </property>
    </bean>

</beans>

另外在/WEB-INF/views下新建一个error.jsp视图。因为上面配置的InternalResourceViewResolver视图解析器默认把error字符串解析为error.jsp视图。error.jsp内容为：

    <h1>Error Page</h1>
    ${requestScope.ex }

下面重新发送index.jsp中的超链接请求后，控制器截获请求并处理请求时，数组越界抛出一个ArrayIndexOutOfBoundsException一个异常，此时由SimpleMappingExceptionResolver异常解析器捕获并把异常映射到error.jsp视图中，通过${requestScope.ex }获取异常。在浏览器中显示为：