Springmvc-简单入门

1,ContextLoaderListener
应用上下文以前是
ApplicationContext app =new ClassPathXmlApplicationContext(“applicationContext.xml”);这样获取的
加载xml配置文件创建容器
每次都会加载配置创建容器 我们想创建加载一次
用监听器放到ServletContext域中 ServletContextListener是监听ServletContext创建的
就可以从servletContext域中获取ApplicationContext对象了

这是自己实现监听器
在web.xml设置全局参数（设置应用上下文对象）配置监听器

    <!--全局初始化参数-->
    <!--<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>applicationContext.xml</param-value>
    </context-param>-->
    <!--配置监听器-->
    <!--<listener>
        <listener-class>com.flatly.listener.ContextLoaderListener</listener-class>
    </listener>-->
    <!--配置springMVC前端控制器-->

public class ContextLoaderListener implements ServletContextListener {
//服务器启动
    public void contextInitialized(ServletContextEvent sce) {
       // ApplicationContext app =new ClassPathXmlApplicationContext("applicationContext.xml");
       //得到servletContext域
        ServletContext servletContext = sce.getServletContext();
        //读取webxml全局参数
       String contextConfigLocation= servletContext.getInitParameter("contextConfigLocation");

        ApplicationContext app =new ClassPathXmlApplicationContext(contextConfigLocation);
        //将Spring应用上下文对象存储到ServletContext域中

        servletContext.setAttribute("app",app);
        System.out.println("spring容器创建完毕");
    }

    public void contextDestroyed(ServletContextEvent sce) {

    }
}

//这是返回应用上下文对象的工具
public class WebApplicationContextUtils {
//需要一个ServletContext域得到app
    public static ApplicationContext getWebApplicationContext(ServletContext servletContext){
        return (ApplicationContext) servletContext.getAttribute("app");
    }
}

@WebServlet(value = "/userServlet")
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     ServletContext servletContext = this.getServletContext();
    // ApplicationContext app = (ApplicationContext) servletContext.getAttribute("app");这里我们不期望还用写app所以创建了Util直接直接给你返回应用上下文对象
      ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
          UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}

Spring提供应用上下文的工具
1.导入坐标
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<dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>
        <dependency>

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在web.xml配置sprig监听器

 <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

使用

public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        WebApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        UserService userService = app.getBean(UserService.class);
        userService.save();
    }
}

SpringMVC快速入门

每个servlet都有共有的行为，接数据封实体，指派实体，还有特有行为
springmvc封装了前端控制器
1，导入坐标
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   <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.0.5.RELEASE</version>
        </dependency>

2,配置servlet配置springmvc核心控制器DispathcerServlet
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  <!--配置springMVC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:spring-mvc.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup><!--服务器启动时加载-->
    </servlet>
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern><!--任何servlet-->
    </servlet-mapping>

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

@Controller
@RequestMapping(value = "/user")
public class UserController {
    //请求地址http://localhost:8080/user/quick
    @RequestMapping("/quick")
    public String save(){
      return "/success.jsp";//加/相当于从当前应用找success.jsp
    }

5配置springmvc核心文件spring-mvc.xml
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 <context:component-scan base-package="com.flatly.controller"/>
 <!--扫描包下带Controller注解的包
<context:component-scan base-package="com.flatly">
    <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
</context:component-scan>
-->

@Controller用于定义Controller类实现Controller接口，实现handleRequest方法返回ModelAndView
@RequestMapping(/xxx)用于url与方法映射

@RequestMapping(
value = “/quick”,
method = RequestMethod.GET,
params = {“username”})//必须限定有请求必须要username

一些组件配置在这里

InternalResourceViewResolver->UrlBasedViewResolver
public static final String REDIRECT_URL_PREFIX = “redirect:”;
public static final String FORWARD_URL_PREFIX = “forward:”;
默认省略forword

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

public InternalResourceViewResolver(String prefix, String suffix) {
this();
this.setPrefix(prefix);
this.setSuffix(suffix);
}可以指定跳转视图的前缀后缀
这里jsp包下有个success.jsp
//return “forword:/jsp/success.jsp”;可以写成 return “success”;//

 配置了视图资源解析器
 在spring-mvc.xml

    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <!--前缀后缀/jsp/xxx/.jsp-->
        <property name="prefix" value="/jsp/"></property>
        <property name="suffix" value=".jsp"></property>
    </bean>

spring-mvc数据响应

1页面调转
1）直接返回字符串
2）通过ModelAndView对象返回
2会写数据
1）直接返回字符串
2）返回对象或集合（json）

通过modelAndView直接返回字符串

   /*
    * Model模型  作用封装数据
    *
    * View 视图 作用展示数据
    * */
  @RequestMapping("/quick2")
    public ModelAndView save2(){
        ModelAndView modelAndView = new ModelAndView();
        //设置模型数据
        //放到了request域中setAttibute
        modelAndView.addObject("username","flatly");
    //设置视图
        modelAndView.setViewName("success");
        return modelAndView;
    }

注入参数ModelAndView 来返回参数不用自己new创建对象

  @RequestMapping("/quick3")
    public ModelAndView save3( ModelAndView modelAndView){

        modelAndView.addObject("username","flatly2");
    //设置视图
        modelAndView.setViewName("success");
        return modelAndView;
    }

视图解析器+Model模型

    @RequestMapping("/quick4")
    public String save4(Model model){
        model.addAttribute("username","flatly3");
        return "success";
    }

注入原始request（不常用）

    @RequestMapping("/quick5")
    public String save5(HttpServletRequest request){
        request.setAttribute("username","flatly4");
        return "success";
    }

回写数据原始注入response（不常用）

    //response.getWriter().print("aaaa")回写
    @RequestMapping("/quick6")
    public void save6(HttpServletResponse response) throws IOException {
       response.getWriter().print("xxx");
    }

直接return字符串使用@ResponseBody注解告知不要跳转页面回写

 @RequestMapping("/quick7")
    @ResponseBody//告诉spring不要页面调转
    public String save7(){
      return "hello flatly";
       }

自己拼接json返回

  @RequestMapping("/quick8")
    @ResponseBody//告诉spring不要页面调转
    public String save8(){
      return "{\"username\":\"zhangsan\",\"age\":18}";//{"username":"zhangsan","age":18}json字符串
       }

借助json工具装换
添加配置坐标jackson

<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>

    @RequestMapping("/quick9")
    @ResponseBody//告诉spring不要页面调转
    public String save9() throws IOException {
           User user = new User("lisi",18);
           //使用json的转换工具
           ObjectMapper objectMapper =new ObjectMapper();
           String json = objectMapper.writeValueAsString(user);
           return json;
       }

spring自己可以自动封装json格式
配置spring-mvc.xml
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   <!--配置处理器映射器-->
<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>

或者直接用这个 不用配处理器映射器
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 <!--mvc注解驱动需要引入mvc命名空间-->
<mvc:annotation-driven"/>

直接return对象或集合

    @RequestMapping("/quick10")
    @ResponseBody//告诉spring不要页面调转
       //期望SpringMVC自动将User转换成json字符串
    public User save10() throws IOException {
           User user = new User("lisi",18);
           return user;
       }

获得请求参数数据

获得普通类型参数
没有会报错

      //获得普通类型参数
       @RequestMapping("/quick11")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
       public void save11(String username,int age) throws IOException {
           System.out.println(username);//http://localhost:8080/user/quick11?username=zhangsan&age=12
           System.out.println(age);
       }

根据请求自动封装实体

	//SpringMVC自动封装POJO对象
       @RequestMapping("/quick12")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
       public void save12(User user) throws IOException {
           System.out.println(user);//User{username='zhangsan', age=12}
       }

获得类似爱好多个 数组类型参数

   //获得数组类型参数
       @RequestMapping("/quick13")
       @ResponseBody //不进行页面跳转不进行数据回写响应体为空
       public void save13(String[] strs) throws IOException {
           System.out.println(Arrays.asList(strs));//http://localhost:8080/user/quick13?strs=aaa&strs=bbb&strs=ccc
         //数组会打印地址list集合重写了toString方法  [aaa, bbb, ccc]
    }

封装集合List list
直接封装不行 得创建VO对象封装

public class VO {
    private List<User> userList;

    public VO() {
    }
    ...

前端

   <form action="${pageContext.request.contextPath}/user/quick14" method="post">
        <%--表明第几个User对象的username--%>
        <input type="text" name="userList[0].username"><br>
        <input type="text" name="userList[0].age"><br>
        <input type="text" name="userList[1].username"><br>
        <input type="text" name="userList[1].age"><br>
        <input type="submit">
    </form>

       //获得集合类型参数
        @RequestMapping(value = "/quick14")
        @ResponseBody //不进行页面跳转不进行数据回写响应体为空
        public void save14(VO vo) throws IOException {
            System.out.println(vo);
            //VO{userList=[User{username='zhangsan', age=12}, User{username='lisi', age=14}]}
            }

当前端发送的是ajax请求json格式时可以直接封装集合
这里用到jquery但是静态资源得有访问权限
在spring-mvc.xml中加入

  <!--开放资源的访问-->
    <mvc:resources mapping="/js/**" location="/js/"/>

  var userList =new Array();
    userList.push({username:"zhangsan",age:18});
    userList.push({username:"lisi",age:18});
    $.ajax(
        {
            type:"POST",
            url:"${pageContext.request.contextPath}/user/quick15",
            data:JSON.stringify(userList),
            contentType:"application/json;charset=utf-8"
        }
    )

@RequestMapping(value = "/quick15")
        @ResponseBody //不进行页面跳转不进行数据回写响应体为空
        public void save15(@RequestBody List<User> userList) throws IOException {
                System.out.println(userList);
    }

如果从前端控制器中找不到则从原始的tomcat中找静态资源
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 <mvc:default-servlet-handler/>

request.setCharacterEncoding->
post请求乱码get方式tomcat8会处理
解决编码配置全局filter过滤器

在web.xml中配置
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    <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>

参数绑定

  @RequestMapping("/quick16")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    /*
    * value与请求参数匹配名称与形参不一样也可以
    * required默认true必须携带参数不然报错false可以不携带
    * defaultValue没有指定参数是则使用默认值
    * */
    public void save16(@RequestParam(value = "name",required = false,defaultValue = "zhangsan") String username) throws IOException {
        System.out.println(username);
    }

解析url地址一部分的参数@PathVrlable占位符

    //licalhost:8080/user/quick17/zhangsan
    @RequestMapping(value = "/quick17/{username}")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    /*
    *restful风格
    * get获取，post新建put更新delete删除
    *  */
    public void save17( @PathVariable(value = "username") String username) throws IOException {
        System.out.println(username);
    }

自定义类型转换器

1，定义转换器实现Converter接口
2，在配置文件中声明转换器
3，在<annotation-driven中引用转换器

   public void save18(Date date) throws IOException {
        System.out.println(date);
    }

date=2014/12/21默认
经常用2022-12-12

//将String转换成Date
public class DateConverter implements Converter<String, Date> {

    @Override
    public Date convert(String dataStr) {
        SimpleDateFormat format =new SimpleDateFormat("yyyy-MM-dd");
        Date date = null;
        try {
            date = format.parse(dataStr);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return date;
    }
}

在spring-mvc.xml中加入

<mvc:annotation-driven conversion-service="conversionService"/>
    <!--声明装换器-->
    <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
        <property name="converters">
            <list>
                <bean class="com.flatly.converter.DateConverter"></bean>
            </list>
        </property>
    </bean>

springmvc获取请求数据

@RequestHeader
相当于request.getHeader(xx)

    @RequestMapping(value = "/quick19")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    public void save19(@RequestHeader(value = "User-Agent",required = false)String user_agent) throws IOException {
        System.out.println(user_agent);
    }

@CookieValue拿到CookieValue

  //直接拿到CookieValue
    @RequestMapping(value = "/quick20")
    @ResponseBody //不进行页面跳转不进行数据回写响应体为空
    public void save20(@CookieValue(value = "JSESSIONID")String jsessionId) throws IOException {
        System.out.println(jsessionId);
    }

用到的注解
@Controller
@RequestMapping
@ResponseBody
@RequestHeader
@RequestParam
@PathVariable
@CookieValue