1. 全局异常概念
在JavaEE项目的开发中，不管是对底层的数据库操作过程，还是业务层的处理过程，还是控制层的处理过程,都不可避免会遇到各种可预知的、不可预知的异常需要处理。
每个过程都单独处理异常，系统的代码耦合度高，工作量大且不好统一,维护的工作量也很大。
SpringMvc对于异常处理这块提供了支持，通过SpringMvc提供的全局异常处理机制，能够将所有类型的异
常处理从各处理过程解耦出来，这样既保证了相关处理过程的功能较单一,也实现了 异常信息的统一处理和维护。
全局异常实现方式Spring MVC处理异常有3种方式
1.使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver;
2.实现Spring的异常处理接口HandlerExceptionResolver自定义自己的异常处理器:
3.使用@ExceptionHandler注解实现异常处理;
2.SimpleMappingExceptionResolver
2.1 mvc.xml
<!-- 全局异常-->
<bean
class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<!-- 页面转发出现异常 设置默认错误页面-->
<property name="defaultErrorView" value="error"></property>
<!-- 错误发生时 设置错误变量名-->
<property name="exceptionAttribute" value="ex"></property>
<!-- 指定异常界面-->
<property name="exceptionMappings">
<props>
<prop key="org.example.ssm.exception.BusinessException">business_error</prop>
</props>
</property>
</bean>
2.2 BusinessException
public class BusinessException extends RuntimeException{
private String msg;
private Integer code=300;
public BusinessException() {
super("BusinessException");
}
public BusinessException(String message) {
super(message);
this.msg=msg;
}
public String getMsg() {
return msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
public Integer getCode() {
return code;
}
public void setCode(Integer code) {
this.code = code;
}
}
2.3 异常位置
@RequestMapping("exe")
public void fun(){
if(true){
System.out.println("BE");
throw new BusinessException("业务异常");
}
}
3.HandlerExceptionResolver
GlobalExceptionResolver类
@Component
public class GlobalExceptionResolver implements HandlerExceptionResolver {
@Override
public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
ModelAndView mv=new ModelAndView("error");
mv.addObject("ex","default error");
if(e instanceof BusinessException){
BusinessException businessException=(BusinessException) e;
mv.setViewName("business_error");
mv.addObject("ex",businessException.getMsg());
}
return mv;
}
}
4.@ExceptionHandler
BaseController类
//要继承BaseController 才可以实现
public class BaseController {
@ExceptionHandler
public String exc(HttpServletRequest request, HttpServletResponse response, Exception e){
request.setAttribute("ex",e);
if(e instanceof BusinessException){
return "business_error";
}
return "error";
}
}
business_error.jsp
<html>
<head>
<title>Title</title>
</head>
<body>
business_error ${ex}
</body>
</html>
5.未捕获异常
web.xml
<!-- 未捕获异常-->
<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>jsp/500.jsp</location>
</error-page>
<error-page>
<error-code>500</error-code>
<location>jsp/500.jsp</location>
</error-page>
<error-page>
<error-code>404</error-code>
<location>jsp/404.jsp</location>
</error-page>