SpringMVC 温习笔记(二)springMVC框架

超、凢脫俗 2022-10-25 04:38 223阅读 0赞

## 什么是springMVC ##

springMVC是一款基于java实现的MVC设计模式的请求驱动类型的轻量级web框架，属于SpringFrameWork的后续产品，已经融合在SpringWebFlow中。SpringMVC是目前最为流行的前端框架之一，在Spring3.0发布之后，全面超越了Struct2框架，成为最优秀的MVC框架。他让一个简单的java类成为处理请求的控制器，而无需实现任何借口，同时还支持RESTful编程风格的请求。

## 图解springMVC执行原理 ##

### springMVC框架基本思想 ###

![springMVC开发步骤图解][springMVC]  
此处值得一提的是springMVC框架他工作要点在于抽取的baseServlet这个模块，而struts2则工作在filter模块中，上述图片是直接采用传智播客老师讲义上的图片，仅供学习讨论。

### springMVC使用要点 ###

首先需要导入dependency，导入的jar包需要参考上一小结案例，保持一致即可。  
依赖

<dependency>
           <groupId>mysql</groupId>
           <artifactId>mysql-connector-java</artifactId>
           <version>5.1.32</version>
       </dependency>
       <dependency>
           <groupId>c3p0</groupId>
           <artifactId>c3p0</artifactId>
           <version>0.9.1.2</version>
       </dependency>
       <dependency>
           <groupId>com.alibaba</groupId>
           <artifactId>druid</artifactId>
           <version>1.1.10</version>
       </dependency>
       <dependency>
           <groupId>junit</groupId>
           <artifactId>junit</artifactId>
           <version>4.12</version>
           <scope>test</scope>
       </dependency>
       <dependency>
           <groupId>commons-fileupload</groupId>
           <artifactId>commons-fileupload</artifactId>
           <version>1.3.3</version>
       </dependency>
    
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-context</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-test</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-web</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>org.springframework</groupId>
           <artifactId>spring-webmvc</artifactId>
           <version>5.0.5.RELEASE</version>
       </dependency>
       <dependency>
           <groupId>javax.servlet</groupId>
           <artifactId>javax.servlet-api</artifactId>
           <version>3.0.1</version>
           <scope>provided</scope>
       </dependency>
       <dependency>
           <groupId>javax.servlet.jsp</groupId>
           <artifactId>javax.servlet.jsp-api</artifactId>
           <version>2.2.1</version>
           <scope>provided</scope>
       </dependency>

web.xml配置文件。

<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>
            <load-on-startup>1</load-on-startup>
        </servlet>
        <servlet-mapping>
            <servlet-name>DispatcherServlet</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>

notes:  
(1)此处的dispatcherServlet就相当于上一小结的ContextLoaderListener类的效用相似。  
(2)此外的init-param标签相当于上一小结中context-param，该参数用来设置springMVC配置文件的参数。  
springMVC配置文件

在配置文件中只需要注明扫描controller包，并将其纳入容器中即可。  
controller 包。  
如果只想扫描web包，还有一种写法如下所示:

<context:component-scan base-package="com.feitian">
        
        <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    </context:component-scan>

UserController类:

@Controller
    /*@RequestMapping("/userController")*/
    public class UserController { 
        @RequestMapping("/save")
        public String save(){ 
            System.out.println("controller save are running");
            return "success.jsp";
        }
    }

### springMVC框架执行流程 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h1ZXNoYW5mZWl0aWFu_size_16_color_FFFFFF_t_70]  
上图是tomcat中springMVC执行的简要流程，接下来看看springMVC详细步骤。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h1ZXNoYW5mZWl0aWFu_size_16_color_FFFFFF_t_70 1]  
在项目中也可对内部资源视图解析器进行手动配置：  
springMVC配置文件

<context:component-scan base-package="com.feitian">
            
            <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
        </context:component-scan>
    
        <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/jsp/"/>
            <property name="suffix" value=".jsp"/>
        </bean>

controller写法

@Controller
    @RequestMapping("/userController")
    public class UserController { 
        @RequestMapping("/save")
        public String save(){ 
            System.out.println("controller save are running");
            //return "/jsp/success";
            return  "success";
        }
    }

notes: 在手动修改InternalResourceViewResolver时，suffix 和prefix 的配置使得我们在返回视图时省略了".jsp"和"/jsp/"。

## springMVC 回写数据 ##

### 页面跳转方式 ###

#### 字符串返回方式 ####

转发过程:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3h1ZXNoYW5mZWl0aWFu_size_16_color_FFFFFF_t_70 2]  
在转真个转发过程中配置了viewResolver后，就对配置的各个环境组装，组装后将完整的解析器返回给前端控制器。  
重定向过程:

return  "redirect:/jsp/success.jsp";

重定向过程及是一个重新请求的过程。

#### ModelAndView返回方式 ####

//1.以新建ModelAndView 变量的方式返回
        @RequestMapping("/save02")
        public ModelAndView save02(){ 
            System.out.println("Controller save02 is running");
            ModelAndView modelAndView = new ModelAndView();
            modelAndView.addObject("username","feitian");
            modelAndView.setViewName("success");
            return modelAndView;
        }
    
        //2.以ModelAndView参数的方式返回
        @RequestMapping("/save03")
        public ModelAndView save03(ModelAndView modelAndView){ 
            System.out.println("Controller save03 is running");
            modelAndView.addObject("username","xueshanfeitian");
            modelAndView.setViewName("success");
            return modelAndView;
        }
    
        //3.用拆分的方式返回ModelAndView
        @RequestMapping("/save04")
        public String save04(Model model){ 
            System.out.println("Controller save04 is running");
            model.addAttribute("username","xueshanfeitian");
            return "success";
        }
    
      //4.以设置request参数的方式返回ModelAndView
        @RequestMapping("/save05")
        public String save05(HttpServletRequest request){ 
            System.out.println("Controller save05 is running");
            request.setAttribute("username","xueshanfeitian");
            return "success";
        }

### 回写数据 ###

#### 直接返回字符串 ####

采用response注入对象回写数据

//1.采用response回写数据
        @RequestMapping("/save06")
        public void save06(HttpServletResponse response)
                throws IOException { 
            System.out.println("Controller save06 is running");
            response.getWriter().println("hello feitian");
        }

**此处需要说明的是ResponseBody注解，该注解是告诉springMVC框架，本返回数据不是去跳转页面，而是要以字符串的形式直接回写数据。**  
采用注解@ResponseBody注解，直接返回字符串。

//2.采用responseBody注解的方式,不进行视图跳转
        @RequestMapping("/save07")
        @ResponseBody
        public String save07() { 
            System.out.println("Controller save07 is running");
            return "{\"username\":\"我是张君的老祖！！！\",\"age\":\"3000\"}";
        }

#### 返回对象或数据 ####

期望将对象或者集合转成jackson对象返回。  
首先需要导入jackson依赖

<dependency>
           <groupId>com.fasterxml.jackson.core</groupId>
           <artifactId>jackson-core</artifactId>
           <version>2.9.0</version>
       </dependency>
       <dependency>
           <groupId>com.fasterxml.jackson.core</groupId>
           <artifactId>jackson-databind</artifactId>
           <version>2.9.0</version>
       </dependency>
       <dependency>
           <groupId>com.fasterxml.jackson.core</groupId>
           <artifactId>jackson-annotations</artifactId>
           <version>2.9.0</version>
       </dependency>

手动转换成jackson对象返回，其本质是与返回字符串是一样的  
采用jackson转换工具转换后，发挥jackson字符串。

@RequestMapping("/save08")
        @ResponseBody
        public String save08() throws JsonProcessingException { 
            System.out.println("Controller save08 is running");
            User user = new User();
            user.setRelation("我是张君的老祖");
            user.setAge(3000);
            ObjectMapper mapper = new ObjectMapper();
            String json = mapper.writeValueAsString(user);
            return  json;
        }

##### 采用修改springMVC配置文件的方式 #####

这种方式本质上是将json转换器配置直接注入到RequestMappingHandlerAdapter即处理器适配器，换种思路就是将RequestMappingHandlerAdapter对象的成员变量messageConverters赋值为MappingJackson2HttpMessageConverter。  
在springMVC中需要加入处理器映射器的配置如下:

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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">
        
        
        <context:component-scan base-package="com.feitian">
            
            <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
        </context:component-scan>
        
        <bean id="viewResolver" class=
                "org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/jsp/"/>
            <property name="suffix" value=".jsp"/>
        </bean>
    
        
        <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
            <property name="messageConverters">
                <list>
                    <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
                </list>
            </property>
        </bean>
    </beans>

测试方法

@RequestMapping("/save09")
        @ResponseBody
        //期望springMVC自动将User转换成json格式的字符串
        public User save09() throws JsonProcessingException { 
            System.out.println("Controller save09 is running");
            User user = new User();
            user.setRelation("我是张君的老祖");
            user.setAge(3000);
            return  user;
        }

采用注册注解驱动方式

<?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 http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
        
        
        <context:component-scan base-package="com.feitian">
            
            <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
        </context:component-scan>
        
        <bean id="viewResolver" class=
                "org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="prefix" value="/jsp/"/>
            <property name="suffix" value=".jsp"/>
        </bean>
    
        
        
        
        <mvc:annotation-driven/>
    </beans>

此处需要注意的是**加入mvc命名空间。** 采用注册注解驱动的这种配置方式，其本质上是将json转换器配置注入到处理器适配器的过程直接在底层实现，及`<mvc:annotation-driven/>`节省了我们以前繁琐的json转换器配置注入过程。  
测试方法可以保持与上面一致save08保持一致

测试方法可以与上面保持一致。

## springMVC处理请求数据 ##

当请求controller时, 则请求参数一般会自动映射  
如本例中小猿的请求如下:  
![在这里插入图片描述][20210205150708361.png]  
controller自动将请求参数映射

@RequestMapping("/save10")
        @ResponseBody
        //期望springMVC自动将User转换成json格式的字符串
        public void save10(String relation,int age) throws JsonProcessingException { 
            System.out.println("Controller save10 is running");
            System.out.println(relation+": 修炼年份"+age);
        }

controller自动将请求参数映射并封装成实体类  
请求地址;  
![在这里插入图片描述][20210205151305640.png]

请求方法如下所示:

@RequestMapping("/save11")
        @ResponseBody
        //期望springMVC自动将User转换成json格式的字符串
        public void save11(User user) throws JsonProcessingException { 
            System.out.println("Controller save11 is running");
            System.out.println(user.getRelation()+": 修炼年份"+user.getAge());
        }

controller自动将请求参数映射并封装成数组  
请求参数  
![在这里插入图片描述][20210205151832260.png]  
请求方法如下所示:

@RequestMapping("/save12")
        @ResponseBody
        public void save12(String  arr []) throws JsonProcessingException { 
            System.out.println("Controller save12 is running");
            System.out.println(Arrays.asList(arr));
        }

采用将集合封装在一个对象的操作方式

请求数据采用表单提交的方式:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
    </head>
    <body>
        <form action="${pageContext.request.contextPath}/userController/save13" method="post">
            <%--表明是第几个user对象的username--%>
            <input type="text" name="userList[0].relation"/><br/>
            <input type="text" name="userList[0].age"/><br/>
            <input type="text" name="userList[1].relation"/><br/>
            <input type="text" name="userList[1].age"/><br/>
            <input type="text" name="userList[2].relation"/><br/>
            <input type="text" name="userList[2].age"/><br/>
            <input type="text" name="userList[3].relation"/><br/>
            <input type="text" name="userList[3].age"/><br/>
            <input type="submit" value="提交">
        </form>
    
    </body>
    </html>

访问jsp页面:  
![在这里插入图片描述][20210207095508401.png]  
挨个填写表单，然后提交即可在控制台看到请求后的数据封装。  
测试类:

@RequestMapping("/save13")
        @ResponseBody
        public void save13(Pojo pojo) throws JsonProcessingException { 
            System.out.println("Controller save13 is running");
            System.out.println(pojo);
        }

其中pojo中有user对象

public class Pojo { 
        private List<User> userList;
        ......
    }

在请求过程中我们会看到控制台答应乱码，我们需要对编码进行处理。  
![在这里插入图片描述][20210207110407186.png]  
**解决乱码问题需要在web.xml中需要配置filter。**

### filter的两种实现方法 ###

#### web.xml配置方式 ####

<?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>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>
            <load-on-startup>1</load-on-startup>
        </servlet>
        <servlet-mapping>
            <servlet-name>DispatcherServlet</servlet-name>
            <url-pattern>/</url-pattern>
        </servlet-mapping>
        
        
        <context-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:applicationContext.xml</param-value>
        </context-param>
        
        
        <listener>
            <listener-class>com.feitian.component.web.listener.ContextLoaderListener</listener-class>
        </listener>
        
        
        <servlet>
            <servlet-name>UserServlet</servlet-name>
            <servlet-class>com.feitian.component.web.servlet.UserServlet</servlet-class>
        </servlet>
        
        
        <servlet-mapping>
            <servlet-name>UserServlet</servlet-name>
            <url-pattern>/userServlet</url-pattern>
        </servlet-mapping>
        
        
        <filter>
            <filter-name>CharacterEncodingFilter</filter-name>
            <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
            <init-param>
                <param-name>encoding</param-name>
                <param-value>UTF-8</param-value>
            </init-param>
        </filter>
        <filter-mapping>
            <filter-name>CharacterEncodingFilter</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>
    </web-app>

#### filter接口实现 ####

通过以上过滤器的配置就可以防止乱码，本质上web.xml配置方式与实现Filter接口的效用是一致的，filter实现结果如下:

@WebFilter("/*")
    public class CharacterFilter implements Filter { 
        public void destroy() { 
        }
        //采用过滤器实现utf-8编码过滤
        public void doFilter(ServletRequest req, ServletResponse resp,
                             FilterChain chain) throws ServletException, IOException { 
            HttpServletRequest request = (HttpServletRequest)req;
            HttpServletResponse response = (HttpServletResponse)resp;
            String method = request.getMethod();
            if(method.equalsIgnoreCase("post")){ 
                request.setCharacterEncoding("utf-8");
            }
            response.setContentType("text/html;charset=utf-8");
            chain.doFilter(request, response);
        }
        public void init(FilterConfig config) throws ServletException { 
        }
    }

上述代码执行效果  
![在这里插入图片描述][2021020711083843.png]  
另外一种请求参数封装方式，采用@RequestBody注解，xml配置方式大体内容与save14保持一致，需要添加关一些开发资源的配置。  
两种方式都可以。

<mvc:default-servlet-handler/>

上述注解是让各位大猿在开发时，**让静态资源轻松躲过拦截的一种配置，相当于在服务器内部让静态资源有了自有行走的通信证。**  
注意查看下面图片，注意两种配置的区别:  
![在这里插入图片描述][20210207103205530.png]  
请求方式

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Title</title>
        <script src="${pageContext.request.contextPath}/js/jquery-3.3.1.js"></script>
        <script>
            var userList = new Array();
            userList.push({ relation:"tom是张君老祖",age:3000});
            userList.push({ relation:"lucy是张君老祖",age:3000});
            userList.push({ relation:"jack是张君老祖",age:3000});
            userList.push({ relation:"hack是张君老祖",age:3000});
            userList.push({ relation:"鹏爷是张君老祖",age:3000});
            $.ajax({ 
                type:"POST",
                url:"${pageContext.request.contextPath}/userController/save14",
                data:JSON.stringify(userList),
                contentType:"application/json;charset=utf-8"
            })
        </script>
    </head>
    <body>
    <h4>ajax</h4>
    </body>
    </html>

测试案例

@RequestMapping("/save14")
        @ResponseBody
        public void save14(@RequestBody List<User> userList) throws JsonProcessingException { 
            System.out.println("Controller save13 is running");
            System.out.println(userList);
        }

当请求参数名与Controller方法接收参数名不一致的情况下，我们可以采用@RequestParam

@RequestMapping("/save15")
        @ResponseBody
        public void save15(@RequestParam("name") String username) throws JsonProcessingException { 
            System.out.println("Controller save15 is running");
            System.out.println(username);
        }

### Restful风格 ###

Restful是一种软件架构风格、设计风格，它不是标准，本质上只是一组设计原则和约束条件，他主要用于客户端和服务器交互的软件。

@RequestMapping("/save16/{name}")
        @ResponseBody
        //建立restful分割
        public void save16(@PathVariable(value = "name",required = false) String username) throws JsonProcessingException { 
            System.out.println("Controller save16 is running");
            System.out.println(username);
    }

访问：

#### 自定义格式转换器 ####

为了防止有些参数请求报错，需要自定义转换器，自定义转换器要实现以下几个要点:

##### 实现Converter接口 #####

//访问方式:http://localhost:8080/springmvc/userController/save16/feitian
    public class DateConverter implements Converter<String,Date> { 
        public Date convert(String dateStr) { 
            Date date = null;
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
            try { 
                 date = simpleDateFormat.parse(dateStr);
            } catch (ParseException e) { 
                e.printStackTrace();
            }
            return date;
        }
    }

##### 在springMVC中声明转换器 #####

......
    
        <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
            <property name="converters">
                <list>
                    <bean class="com.feitian.component.converter.DateConverter"/>
                </list>
            </property>
        </bean>
    ......

##### 在annotation-driven 中引用转换器 #####

......
    
    <mvc:annotation-driven conversion-service="conversionService" />
    ......

访问

http://localhost:8080/springmvc/userController/save17/2019-10-28

测试方法成功运行  
![在这里插入图片描述][20210208140024562.png]

##### 获得请求头 #####

有些情况下我们需要获取请求头信息：获取方法所如下

@RequestMapping("/save18")
        @ResponseBody
        //建立restful分割
        public void getContent18(@RequestHeader(value = "User-Agent",required = false)
                                   String contentHeader) throws JsonProcessingException { 
            System.out.println("Controller save17 is running");
            System.out.println(contentHeader);
        }
    
        @RequestMapping("/save19")
        @ResponseBody
        //获取jsessionID
        public void getContent19(@CookieValue(value = "JSESSIONID",required = false)
                                         String JSID) throws JsonProcessingException { 
            System.out.println("Controller save17 is running");
            System.out.println(JSID);
        }

上面两种方法分别介绍了如何获取请求头的两种方式，其中获取cookie是比较常见，希望各位猿能记住这个方法。

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