Spring中的异常处理（兼顾AJAX和FORM）

总结了一下在使用SPRING开发过程中使用的异常处理方式，查找了一些资料，并在此作为记录。

统一异常处理-使用默认Resolver

使用SimpleMappingExceptionResolver进行处理，这样controller层不需要捕获异常，Spring框架会进行处理。SimpleMappingExceptionResolver是spring的默认实现，但是无法处理AJAX的异常解析

<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
   <property name="defaultErrorView" value="error"></property>
   <property name="exceptionAttribute" value="ex"></property>
   <property name="exceptionMappings">
       <props>
           <prop key="IOException">exception/ioexception</prop>
           <prop key="SQLException">exception/dbexception</prop>
       </props>
   </property>
</bean>

统一异常处理- 使用自定义异常处理器

* 新建自定义异常处理器

public class MyExceptionHandler implements HandlerExceptionResolver{
    public ModelAndView resolveException(HttpServletRequest request , HttpServletResponse response,Object handler,Exception ex){
        Map<String,Object> model = new HashMap<String , Object>();
        model.put("ex",ex);
        if(ex instanceof ExceptionA){
            return new ModelAndView("exception/exception_a",model);
        }else if(ex instanceof ExceptionB){
            return new ModelAndView("exception/exception_b",model);
        }else{
            return new ModelAndView("exception/exception_a",model);
        }
    }
}

* 新建自定义异常页面
* bean声明

<bean id="exceptionHandler" class="com.springapp.exception.MyExceptionHandler"></bean>

统一异常处理-使用@ExceptionHandler注解

* 在Controller的基类中声明方法，这种方法无需任何配置（当然要注解扫描）

@ExceptionHandler
public String expaaa(HttpServletRequest request, Exception ex) {
    request.setAttribute("ex", ex);
    if(ex instanceof ExceptionA){
        return "exception/exception_a";
    }else if(ex instanceof ExceptionB){
        return "exception/exception_b";
    }else{
        return "exception/exception_a";
    }
}

* 其他Controller继承上面的基类

统一异常处理-未捕获异常的处理
在web.xml中定义

<error-page>
    <exception-type>java.lang.Throwable</exception-type>
    <location>/500.jsp</location>
</error-page>
<error-page>
    <error-code>500</error-code>
    <location>/500.jsp</location>
</error-page>
<error-page>
    <error-code>404</error-code>
    <location>/404.jsp</location>
</error-page>

大一统-包含表单和AJAX异常处理

* 增加自定义异常处理器，同时如果是AJAX请求，会返回对应的错误回应

public class GlobalExceptionResolver extends SimpleMappingExceptionResolver {
    protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response,Object handler, Exception ex){
        String viewName = determineViewName(ex,request);
        response.setCharacterEncoding("UTF-8");
        if(viewName!=null){
            if (!(request.getHeader("accept").contains("application/json")  ||
                    ( request.getHeader("X-Requested-With")!= null  && request.getHeader("X-Requested-With").contains("XMLHttpRequest") ) )) {
                Integer statusCode = determineStatusCode(request,viewName);
                if(statusCode !=null){
                    applyStatusCodeIfPossible(request,response,statusCode);
                }
                System.out.println("JSP Format Return" + viewName);
                return getModelAndView(viewName,ex,request);

            }else{
                try{
                    PrintWriter writer = response.getWriter();
                    writer.write(ex.getMessage());
                    writer.flush();
                }catch(IOException e){
                    e.printStackTrace();
                }
                System.out.println("JSP Format Return" + viewName);
                return null;
            }
        }else{
            return null;
        }
    }
}

* 配置exceptionresolver

<bean id="exceptionResolver" class="com.springapp.exception.GlobalExceptionResolver">
    <!-- 定义默认的异常处理页面，当该异常类型的注册时使用 -->
    <property name="defaultErrorView" value="error"></property>
    <!-- 定义异常处理页面用来获取异常信息的变量名，默认名为exception -->
    <property name="exceptionAttribute" value="ex"></property>
    <!-- 定义需要特殊处理的异常，用类名或完全路径名作为key，异常也页名作为值 -->
    <property name="exceptionMappings">
        <props>
            <prop key="IOException">exception/ioexception</prop>
            <prop key="java.sql.SQLException">exception/dbexception</prop>
            <prop key="com.springapp.exception.ExceptionA">exception/exception_a</prop>
            <prop key="com.springapp.exception.ExceptionB">exception/exception_b</prop>
        </props>
    </property>

</bean>

* DONE