2.SpringMVC框架快速入门

- SpringMVC

• 原理


• 开发步骤
  1. 导入SpringMVC相关坐标
  2. 配置SpringMV核心控制器·DispatherSerclet
  3. 创建Controller类和视图页面
  4. 使用注解配置Controller类中业务方法的映射地址
  5. 配置SpringMVC核心文件spring-mvc.xml

- web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <servlet>
        <servlet-name>SpringMVC</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring-mvc.xml</param-value><!--spring-mvc的配置映射-->
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>SpringMVC</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
    <!--配置乱码过滤器-->
    <filter>
        <filter-name>encoding</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/</url-pattern>
    </filter-mapping>
</web-app>

- spring-mvc配置

<?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"
       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/context
                           https://www.springframework.org/schema/context/spring-context.xsd
                           http://www.springframework.org/schema/mvc
                           https://www.springframework.org/schema/mvc/spring-mvc.xsd">
    	<!--扫描1. controller包-->
        <context:component-scan base-package="com.controller"/>
        <mvc:default-servlet-handler/>
       
		<!--2. 配置视图解析器-->
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
            <!--2.1 页面前缀-->
            <property name="prefix" value="/"/>
            <!--2.2 页面后缀-->
            <property name="suffix" value=".jsp"/>
        </bean>
    	<!--3. 开启mvc注解驱动-->
    	<mvc:annotation-driven/>
</beans>

	<!--Json乱码问题解决-->
    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

- 注解说明

注解	说明
@Controller	使用在web层实例化Bean
@RequestMapping	用于映射url到控制器类或一个特定的处理方法程序，可用于类或方法上；在类上表示所有响应请求的方法都是以该地址作为父路径
@RequestParam(“username”)	限定前端参数的name为username
@ResponseBody	不会走视图解析器，会直接返回字符串，作用在方法上搭配@Controller使用
@RestController	作用在类上，不走视图解析器，可代替@ResponseBody使用，其所作用的类下所有方法都只会返回字符串

- 重定向和转发

package com.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class list {
    @RequestMapping("/start")
    public String tes(){
        //转发方式一：‘/’+index.jsp
        return "/index.jsp";
    }
    
     @RequestMapping("/start")
    public String tes(){
        //转发方式二：forword:/index.jsp
        return "forword:/index.jsp";
    }
    
     @RequestMapping("/start")
    public String tes(){
        //重定向：redirect:/index.jsp
        return "redirect:/index.jsp";
    }
}

- 接受请求参数和数据回显

• usercontroller

@Controller
@RequestMapping("/user")
public class userController {

    //localhost:8080/user/t1? name=xxx
    @GetMapping("/t1")
    public String test1(user u, Model model){
        //1.前端接受参数
        System.out.println("接收参数为"+u.toString());
        //2.将返回的结果传递给前端。Model
        model.addAttribute("msg",u);
        //3.视图跳转
        return "index";
    }
}

• index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>Success!${msg["name"]}</h1>
<h1>Success!${msg["address"]}</h1>
<h1>Success!${msg["age"]}</h1>

</body>
</html>

- JSON

导入json

乱码解决(在spring-mvc中导入)

<!--Json乱码问题解决-->
    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

Jackson使用

package com.controller;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import com.pojo.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;


@Controller
public class JsonController {

    @ResponseBody
    @RequestMapping("/j1")
    public String Json1() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        User user1 = new User("法外狂徒", "联盟峡谷", 20);
        return mapper.writeValueAsString(user1);
        //返回对象
    }
    @ResponseBody
    @RequestMapping("/j2")
    public String Json2() throws JsonProcessingException {
        ObjectMapper mapper1 = new ObjectMapper();
        List<User> userList=new ArrayList<User>();
        userList.add(new User("赵信","峡谷草丛",18));
        userList.add(new User("赵信","峡谷草丛",18));
        userList.add(new User("赵信","峡谷草丛",18));
        return mapper1.writeValueAsString(userList);
        //返回对象数组
    }

    @ResponseBody
    @RequestMapping("/j3")
    public String Json3() throws JsonProcessingException {
        ObjectMapper mapper1 = new ObjectMapper();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return mapper1.writeValueAsString(sdf.format(new Date()));
        //返回时间序列
    }
}

- 拦截器配置

自定义配置

1. web.xml中配置

    <?xml version="1.0" encoding="UTF-8"?>
   <web-app xmlns="http://java.sun.com/xml/ns/javaee"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
   		  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
            version="3.0">
       <!--前端控制器-->
       <servlet>
           <servlet-name>dispatcherServlet</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>
       </servlet>
       
       <servlet-mapping>
           <servlet-name>dispatcherServlet</servlet-name>
           <!--只不匹配jsp-->
           <url-pattern>/</url-pattern>
       </servlet-mapping>
   
   </web-app>

2. Springmvc.xml中配置

   <?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"
          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/context
                              https://www.springframework.org/schema/context/spring-context.xsd
                              http://www.springframework.org/schema/mvc
                              https://www.springframework.org/schema/mvc/spring-mvc.xsd">
   <context:component-scan base-package="cn.justweb"/>
   <bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
       <property name="prefix" value="/WEB-INF/views/"></property>
       <property name="suffix" value=".jsp"></property>
   </bean>
   
     <!--注解驱动，自动注入mvc里面的组件-->
   <mvc:annotation-driven/>
   
   <!--自定义拦截器的配置-->
   
   <!--先配谁先执行谁-->
   <mvc:interceptors>
       
       <!--配置对哪些资源进行拦截操作-->
       <mvc:mapping path="/**"/>
       
       <!--配置对哪些资源排除拦截操作,例如登陆和注册-->
       <mvc:exclude-mapping path="/user/login"/>
       <mvc:exculde-mapping path="/user/regist"/>
       <!--拦截器类-->
       <bean class="cn.justweb.interceptor.FirstInterceptor"></bean>
       <bean class="cn.justweb.interceptor.SecInterceptor"/>
       
   </mvc:interceptors>	
   </beans>

3. 定义一个拦截器FirstInterceptor，实现HandlerInterceptor接口，并重写其中的三个方法

4. 第一个拦截器

   //配置的第一个拦截器
     public class FirstInterceptor implements HandlerInterceptor {
         /**
          * 执行流程：
          * 拦截器的preHandle方法执行了
          * controller中的testInterceptor方法
          * 拦截器postHandle方法执行了
          * 拦截器的afterCompletion执行了
          * */
         @Override
         public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
             System.out.println("拦截器的preHandle方法执行了");
             //此处为true的时候才执行下面的事情
             return true;
         }
     
         @Override
         public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
             System.out.println("拦截器postHandle方法执行了");
         }
     
         @Override
         public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
             System.out.println("拦截器的afterCompletion执行了");
         }
     }

5. 第二个拦截器

   //配置的第二个拦截器
      public class SecInterceptor implements HandlerInterceptor {
          /**
           * 执行流程：
           * 拦截器的preHandle方法执行了
           * 拦截器2的preHandle方法执行了
           * controller中的testInterceptor方法
           * 拦截器2的postHandle方法执行了
           * 拦截器postHandle方法执行了
           * 拦截器2的afterCompletion方法执行了
           * 拦截器的afterCompletion执行了
           * */
          @Override
          public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
              System.out.println("拦截器2的preHandle方法执行了");
              return true;
          }
      
          @Override
          public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
              System.out.println("拦截器2的postHandle方法执行了");
      
          }
      
          @Override
          public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
              System.out.println("拦截器2的afterCompletion方法执行了");
      
          }
      }

6. 测试

   @Controller
     public class SpringMVCHandler {
         @RequestMapping("/testInterceptor")//拦截器
         public String testInterceptor(){
             System.out.println("controller中的testInterceptor方法");
             return "success";
         }
     }

- 异常处理

* 处理异常的两种处理方式

1. 简单异常处理器(在springmvc.xml中配置)

2. 自定义异常处理类（ 实现HandlerExceptionResolver 接口）

   <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
      <!--默认错误视图-->
       <property name="defaultErrorView" value="error"></property>
       
       <property name="exceptionMappings">
           <map>
               <entry key="也可以是自定义异常类" value="错误视图"></entry>
               <entry key="java.lang.ClassCastException" value="error"></entry>
           </map>
       </property>
   </bean>

3. 使用@ExceptionHandler注解实现异常处理(在controller中使用)。

   @ExceptionHandler({自定义异常处理类.class})
   public String exception(MyException e){
       System.out.printrl(e.getMessage());
       e.printStackTrance();
       return "exception";
   }