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SpringMVC异常处理

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1、springMVC 异常处理概述

1.1、springMVC 中的异常

在程序开发中,不管是那层的业务,都会不可避免的出现异常处理。如果每层单独处理异常,那么系统的代码的耦合度就会提高。而且工作量也会加大,不好处理。

而 springMVC 将所有类型的异常从各层解耦出来,进行异常的统一处理和维护。

springMVC 异常处理有三种:

简单异常处理器 SimpleMappingExceptionResolver。

异常处理接口 HandlerExceptionResolver 自定义自己的异常处理器。

@ExceptionHandler 注解实现异常处理。

1.2、异常处理结构图

SpringMVC 异常处理

1.3、异常处理前的准备

1.3.1、需求

完成 springMVC 异常处理,创建三层架构(dao\service\view)

1.3.2、创建新项目

创建一个 maven 项目 smvc005

1.3.3、导入 jar 包

pom.xml

<properties> <spring.version>5.2.2.RELEASE</spring.version> </properties> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> </dependencies>

1.3.4、配置 web.xml

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"> <display-name>Archetype Created Web Application</display-name> <!-- 配置 SpringMVC 核心, 前置控制器 DispatcherServlet --> <servlet> <servlet-name>SpringMVCDispathcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <!-- 配置初始化参数,用来读取 springmvc.xml 文件 --> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/springmvc.xml</param-value> </init-param> <!-- 配置 servlet 的对象的创建时间点:应用加载时创建。取值只能是非 0 正整数,表示启动顺序 --> <load-on-startup>1</load-on-startup> </servlet> <!-- 前置控制器,映射所有地址 --> <servlet-mapping> <servlet-name>SpringMVCDispathcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> </web-app>

1.3.5、配置 springmvc.xml

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:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <!-- 配置扫描器,扫描注解 --> <context:component-scan base-package="com.tyschool.smvc004"></context:component-scan> <!-- 配置视图解析器,配置前缀和后缀 --> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/pages/"></property> <property name="suffix" value=".jsp"></property> </bean> </beans>

1.3.6、启动服务

http://localhost:8080/smvc004/index.jsp

2、配置各层异常

2.1、自定义异常类

DemoException.java

public class DemoException extends Exception {public DemoException(){} public DemoException(String message){super(message); } }

2.2、dao 层

ExceptionDao.java

package com.tyschool.smvc004.dao; import com.tyschool.smvc004.utils.DemoException; import org.springframework.stereotype.Repository; import java.sql.SQLException; @Repository("exceptionDao") public class ExceptionDao {public void dbDao() throws Exception{throw new SQLException("数据库异常 -dao"); } public void myDao() throws Exception{throw new DemoException("自定义异常 -dao"); } public void noDao() throws Exception{throw new SQLException("未知异常 -dao"); } }

2.3、service 层

IExceptionService.java

public interface IExceptionService {public void myService()throws Exception; public void dbService()throws Exception; public void noService()throws Exception; public void myDao()throws Exception; public void dbDao()throws Exception; public void noDao()throws Exception; }

ExceptionServiceImpl.java

import com.tyschool.smvc004.dao.ExceptionDao; import com.tyschool.smvc004.service.IExceptionService; import com.tyschool.smvc004.utils.DemoException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import java.sql.SQLException; @Service("exceptionServiceImpl") public class ExceptionServiceImpl implements IExceptionService {@Autowired private ExceptionDao exceptionDao; @Override public void myService() throws Exception {throw new DemoException("自定义异常 -Service"); } @Override public void dbService() throws Exception {throw new SQLException("数据库异常 -Service"); } @Override public void noService() throws Exception {throw new SQLException("未知异常 -Service"); } @Override public void myDao() throws Exception {exceptionDao.myDao(); } @Override public void dbDao() throws Exception {exceptionDao.dbDao(); } @Override public void noDao() throws Exception {exceptionDao.noDao(); } }

2.4、控制器 controller

ExceptionController.java

import com.tyschool.smvc004.service.IExceptionService; import com.tyschool.smvc004.utils.DemoException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import java.sql.SQLException; @Controller("exceptionController") public class ExceptionController {@Autowired @Qualifier("exceptionServiceImpl") private IExceptionService exceptionService; @RequestMapping("/db") public void db() throws Exception{throw new SQLException("数据库异常 -Controller"); } @RequestMapping("/my") public void my() throws Exception{throw new DemoException("自定义异常 -Controller"); } @RequestMapping("/no") public void no() throws Exception{throw new SQLException("未知异常 -Controller"); } @RequestMapping("/dbS") public void dbService() throws Exception{exceptionService.dbService(); } @RequestMapping("/myS") public void myService() throws Exception{exceptionService.myService(); } @RequestMapping("/noS") public void noServcie() throws Exception{exceptionService.noService(); } @RequestMapping("/dbD") public void dbDao() throws Exception{exceptionService.dbDao(); } @RequestMapping("/myD") public void myDao() throws Exception{exceptionService.myDao(); } @RequestMapping("/noD") public void noDao() throws Exception{exceptionService.noDao(); } }

3、创建 view 层

3.1、首页

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> </head> <body> <h3><a href="${pageContext.request.contextPath}/dbD"> 处理 dao 中数据库异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/myD"> 处理 dao 中自定义异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/noD"> 处理 dao 未知异常 </a></h3> <hr> <h3><a href="${pageContext.request.contextPath}/dbS"> 处理 service 中数据库异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/myS"> 处理 service 中自定义异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/noS"> 处理 service 未知异常 </a></h3> <hr> <h3><a href="${pageContext.request.contextPath}/db"> 处理 controller 中数据库异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/my"> 处理 controller 中自定义异常 </a></h3> <h3><a href="${pageContext.request.contextPath}/no"> 处理 controller 未知异常 </a></h3> <hr> <!-- 在 web.xml 中配置404 --> <h3> <a href="${pageContext.request.contextPath}/404">404 错误 </a> </h3> </body> </html>

3.2、404

404.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>404</title> </head> <body> 没能找到资源!</body> </html>

3.3、error

/pages/error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isErrorPage="true"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>error</title> </head> <body> <H1> 未知错误:</H1><%=exception %> <H2> 错误内容:</H2> <% exception.printStackTrace(response.getWriter()); %> </body> </html>

3.4、my-error

/pages/my-error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isErrorPage="true"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>my-error</title> </head> <body> <H1> 自定义异常错误:</H1><%=exception %> <H2> 错误内容:</H2> <% exception.printStackTrace(response.getWriter()); %> </body> </html>

3.5、sql-error

/pages/sql-error.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isErrorPage="true"%> <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>sql-error</title> </head> <body> <H1> 数据库异常错误:</H1><%=exception %> <H2> 错误内容:</H2> <% exception.printStackTrace(response.getWriter()); %> </body> </html>

3.6、测试

http://localhost:8080/smvc004/index.jsp

4、SimpleMappingExceptionResolver

org.springframework.web.servlet.handler.SimpleMappingExceptionResolver

springmvc.xml

<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <!-- 定义默认的异常处理页面,当该异常类型注册时使用 --> <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="exception"></property> <!-- 定义需要特殊处理的异常,用类名或完全路径名作为 key,异常页名作为值 --> <property name="exceptionMappings"> <props> <prop key="com.tyschool.smvc004.utils.DemoException">my-error</prop> <prop key="java.sql.SQLException">sql-error</prop> <!-- 在这里还可以继续扩展对不同异常类型的处理 --> </props> </property> </bean>

404 配置

<error-page> <error-code>404</error-code> <location>/404.jsp</location> </error-page>

5、HandlerExceptionResolver

org.springframework.web.servlet.HandlerExceptionResolver

5.1、加入 jar 包

<dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>4.0.1</version> <scope>provided</scope> </dependency>

5.2、MyExceptionHandler

MyExceptionHandler.java

import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.sql.SQLException; import java.util.HashMap; import java.util.Map; public class MyExceptionHandler implements HandlerExceptionResolver {@Override public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {Map<String,Object> model=new HashMap<String,Object>(); model.put("exception",e); if(e instanceof DemoException){return new ModelAndView("my-error",model); }else if(e instanceof SQLException){return new ModelAndView("sql-error",model); }else{return new ModelAndView("error",model); } } }

5.3、配置 bean

Springmvc.xml

<bean class="com.tyschool.smvc004.utils.MyExceptionHandler"></bean>

5.4、测试

http://localhost:8080/smvc004/index.jsp

6、@ExceptionHandler

6.1、创建异常处理类

BaseController.java

import com.tyschool.smvc004.utils.DemoException; import org.springframework.web.bind.annotation.ExceptionHandler; import javax.servlet.http.HttpServletRequest; import java.sql.SQLException; public class BaseController {/** 基于 @ExceptionHandler 异常处理 */ @ExceptionHandler public String exception(HttpServletRequest request, Exception ex) {request.setAttribute("exception", ex); // 根据不同错误转向不同页面,即异常与 view 的对应关系 if (ex instanceof SQLException) {return "sql-error"; } else if (ex instanceof DemoException) {return "my-error"; } else {return "error"; } } }

6.2、创建新控制器

TestExceptionController.java

import com.tyschool.smvc004.service.IExceptionService; import com.tyschool.smvc004.utils.DemoException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import java.sql.SQLException; @Controller("testExceptionController") public class TestExceptionController extends BaseController {@Autowired @Qualifier("exceptionServiceImpl") private IExceptionService exceptionService; @RequestMapping("/db") public void db() throws Exception{throw new SQLException("数据库异常 -Controller"); } @RequestMapping("/my") public void my() throws Exception{throw new DemoException("自定义异常 -Controller"); } @RequestMapping("/no") public void no() throws Exception{throw new SQLException("未知异常 -Controller"); } @RequestMapping("/dbS") public void dbService() throws Exception{exceptionService.dbService(); } @RequestMapping("/myS") public void myService() throws Exception{exceptionService.myService(); } @RequestMapping("/noS") public void noServcie() throws Exception{exceptionService.noService(); } @RequestMapping("/dbD") public void dbDao() throws Exception{exceptionService.dbDao(); } @RequestMapping("/myD") public void myDao() throws Exception{exceptionService.myDao(); } @RequestMapping("/noD") public void noDao() throws Exception{exceptionService.noDao(); } }

6.3、测试

http://localhost:8080/smvc004/index.jsp

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