SpringMVC简介(网摘)

SpringMVC 全称是 Spring Web MVC，是spring框架一部分，是一个 mvc 的框架，和struts2一样是一个表现层框架。

SpringMVC 是 Spring 家族的一员，Spring是将现在开发中流行的组件进行组合而成的一个框架！它用在基于MVC的表现层开发，类似于struts2框架

mvc 是一种设计模式。设计模式理解为最佳实践。

一、配置 SpringMVC

导入相应的包

pom.xml
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<!--单元测试-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
    <scope>test</scope>
</dependency>

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.1.3.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.mchange/c3p0 -->
<dependency>
    <groupId>com.mchange</groupId>
    <artifactId>c3p0</artifactId>
    <version>0.9.5.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.13</version>
</dependency>

<!-- https://mvnrepository.com/artifact/cglib/cglib -->
<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.2.10</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-aspects -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aspects</artifactId>
    <version>5.1.2.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-test -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>5.1.3.RELEASE</version>
    <scope>test</scope>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-dbcp/commons-dbcp -->
<dependency>
    <groupId>commons-dbcp</groupId>
    <artifactId>commons-dbcp</artifactId>
    <version>1.4</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-pool/commons-pool -->
<dependency>
    <groupId>commons-pool</groupId>
    <artifactId>commons-pool</artifactId>
    <version>1.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>5.1.3.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-orm -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-orm</artifactId>
    <version>5.1.3.RELEASE</version>
</dependency>


<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>1.3.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-web -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>5.1.3.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>5.1.3.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/jstl/jstl -->
<dependency>
    <groupId>jstl</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/taglibs/standard -->
<dependency>
    <groupId>taglibs</groupId>
    <artifactId>standard</artifactId>
    <version>1.1.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/javax.servlet/servlet-api -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>servlet-api</artifactId>
    <version>2.5</version>
    <scope>provided</scope>
</dependency>

Spring的配置文件

springmvc.xml
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<?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">
    <!-- 启用注解 扫描路径下的包 -->
    <context:component-scan base-package="net.togogo.controller"></context:component-scan>

    <!--启用mvc注解-->
    <mvc:annotation-driven />
</beans

Servlet的配置文件

顺序不能错，之前试过把 <filter> 放 <sevlet> 后面，报错了。

web.xml
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<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>

  <!--强制转utf-8解决中文乱码-->
  <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>
    <init-param>
      <param-name>forceEncoding</param-name>
      <param-value>true</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  
  <!--引入springmvc-->
  <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:springmvc.xml</param-value>
    </init-param>
  </servlet>

  <servlet-mapping>
    <servlet-name>springmvc</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>

</web-app>

二、Hello, Contoroller !

一个简单的例子体会 SpringMVC 的神奇

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package net.togogo.controller;

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

@Controller
public class HelloController {
    //localhost:8080/SpringProject/hello.do
    @RequestMapping("/hello")
    public String sayHello() {
        System.out.println("-----HelloController.sayHello()-----");
        return "Hello.html";
    }
}

@Controller 、 @Service 、@Repository 这三个注解的作用其实跟 @Component 一样，属于它的别名(不知道能不能这样理解)，它方便程序员们区分这个类是属于哪个层面的。

  • @Repository 对应持久层，也就是dao层
  • @Service 对应业务层
  • @Controller 对应控制层(视图层)，也就是 servlet

在 web.xml 里，配置了匹配 *.do 结尾的 url 交由 SpringMVC 处理，SpringMVC 去寻找声明为控制层的类，然后匹配相对应的 @RequestMapping 注解的方法，执行里面的内容。返回的 Hello.html 即为要显示给用户的前台页面，文件在 webapp/Hello.html

限制 Get/Post 方法

在 @RequestMapping 里指定 method 值就可以了，如：

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@Controller
public class GetPost {
    //只能通过get方法
    @RequestMapping(value = "/onlyget", method = RequestMethod.GET)
    public String onlyGet() {
        System.out.println("-----onlyGet()-----");
        return "Hello.html";
    }

    //只能通过post方法
    @RequestMapping(value = "/onlypost", method = RequestMethod.POST)
    public String onlyPost() {
        System.out.println("-----onlyPost()-----");
        return "Hello.html";
    }

    //get和post都可以
    @RequestMapping(value = "/getandpost", method = {RequestMethod.POST,RequestMethod.GET})
    public String GetAndPost() {
        System.out.println("-----GetAndPost-----");
        return "Hello.html";
    }
}

获取页面传递过来的参数

传统方式获取

传入 HttpServletRequest 和 HttpServletResponse，然后通过 .getParameter() 方法获取

getParameter.java
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@Controller
public class getParameter {
    //接收页面传递的参数
    @RequestMapping("/getparameter")
    public String getParameter(HttpServletRequest request, HttpServletResponse response, HttpSession session, Model model) {
        String id = request.getParameter("id");
        model.addAttribute("id", id);
        model.addAttribute("session", session);
        return "/getparameter.jsp";
    }
}

注解方式获取

使用 @RequestParam 注解 (Get/Post 都能用)，该注解有两个参数：

  • value: 传入值的名称
  • required： 是否必须传来该参数 (为 true 时如果客户端没传来该参数会报400错误)
  • defaultValue：默认值，如果客户端没有传来该参数，那么就会指认该默认值。
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 @RequestMapping("/getparameter2") //getparamater2.do?id=1 则输出1
public void getParameter(@RequestParam(value = "id", required = true) String aaa) {
    System.out.println(aaa);
}

value值可以省略，省略的话，入参的名字就是要获取的参数的id，例：

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 @RequestMapping("/getparameter2") //getparamater2.do?id=1 则输出1
public void getParameter(@RequestParam(required = true) String id) {
    System.out.println(id);
}

URL占位符

通过在方法中使用 @PathVariable 获取 @RequestMapping 中的 {×××} 中的 ××× 变量。

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@Controller
public class ZhanWeiFu {
    //1个占位符
    @RequestMapping("/getuser/{userid}")
    public String singleZhanWeiFu(@PathVariable String userid, Model model) {
        model.addAttribute("userid", userid);
        return "/ZhanWeiFu.jsp";
    }
    //多个占位符
    @RequestMapping("/getuser/{groupid}/{userid}")
    public String multiZhanWeiFu(@PathVariable String groupid, @PathVariable String userid, Model model) {
        model.addAttribute("groupid", groupid);
        model.addAttribute("userid", userid);
        return "/ZhanWeiFu.jsp";
    }
}

checkbox 的获取

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<form action="${pageContext.request.contextPath}/getcheckbox.do" method="post">
    <input type="checkbox" name="checkid" value="001"/>
    <input type="checkbox" name="checkid" value="002"/>
    <input type="checkbox" name="checkid" value="003"/>
    <input type="checkbox" name="checkid" value="004"/>
    <input type="submit"/>
</form>
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@Controller
public class GetCheckBox {
    @RequestMapping("/getcheckbox")
    public void getCheckbox(String[] checkid) {
        String a = Arrays.toString(checkid);
        System.out.println(a);
    }
}

输出结果（全选时）：

[001, 002, 003, 004]

获取对象信息

假设有一个 pojo 类 User：

User.java
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public class User {
    private int id;
    private String username;
    private String password;
    private int level;
    private String avatar;
    
    //省略各种方法..
}

前台的表格中，name属性名要与 pojo 类的属性名一一对应，然后 SpringMVC 便会自动将属性设置到 pojo 对象中

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<form action="${pageContext.request.contextPath}/getuserpojo.do" method="post">
    <input type="text" name="id" value="1"/>
    <input type="text" name="username" value="crazykid"/>
    <input type="text" name="password" value="123456"/>
    <input type="text" name="level" value="0"/>
    <input type="text" name="avatar" value=""/>
    <input type="submit"/>
</form>

Controller:

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@Controller
public class getUserPojo {
    @RequestMapping("/getuserpojo")
    public void getUserPojo(Model model, User user) {
        System.out.println(user);
    }
}

输出结果：

User{id=1, username=’crazykid’, password=’123456’, level=0, avatar=’’}

使用 @CookieValue 注解

  • value : 要获取的 Cookie 名字

  • required：是否必须

如果 required = false ，客户端没有传过来该 Cookie ，就会报400错误：

Missing cookie ‘XXXXX’ for method parameter of type String

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@Controller
public class GetCookie {
    @RequestMapping("/getcookie")
    public void GetCookie(@CookieValue(value = "JSESSIONID",required = true) String sessionId, Model model) {
        System.out.println(sessionId);
    }
}

转发页面

redirect 方法

相当于 response.sendRedirect()，浏览器地址发生变化，执行一个新的 request 和 response。如果有 model 数据，会自动在 URL 后面加上 GET 参数。

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@RequestMapping("/redirect")
public String Redirect(Model model) {
    model.addAttribute("id",123);
    return "redirect:/redirect.jsp"; //浏览器地址会变成 redirect.jsp&id=123
}

forward 方法

相当于 request.getRequestDispatcher().forward(request,response)，浏览器地址不发生变化，同时继承原来的 request 和 response，model 也可以继承

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@RequestMapping("forward")
public String Forward(Model model) {
    model.addAttribute("id",123);
    return "forward:/redirect.jsp"; //浏览器地址还是forward.do
}

接收与返回 JSON 数据

接收JSON

首先导入相应的包

pom.xml
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<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.9.8</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.8</version>
</dependency>

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.9.0</version>
</dependency>

还是刚才的 User：

User.java
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public class User {
    private int id;
    private String username;
    private String password;
    private int level;
    private String avatar;
    
    //省略各种方法..
}

前台用 Ajax 提交 Json 数据到后台：

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<a href="javascript:void(0)" id="senddata">点我发送数据</a>

<script type="application/javascript" src="js/jquery-3.3.1.min.js"></script>
<script type="application/javascript">
    $(function () {
        $("#senddata").click(function(){
            $.ajax({
                type: 'post',
                url: '${pageContext.request.contextPath}/requestbody.do',
                contentType:'application/json;charset=utf-8',
                data: JSON.stringify({
                    id: "1",
                    username: "crazykid",
                    password: "123456",
                    level: "1",
                    avatar: "default.jpg"
                }),
                success: function(data){
                    alert("发送成功啦");
                }
            })
        })
    })
</script>

控制器用 @RequestBody 注解将 Json 数据转换为对象：

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@Controller
public class RequestBodyTest {
    @RequestMapping("/requestbody")
    public String RequestBody(@RequestBody User user) {
        System.out.println(user);
        return "Hello.html"; //随便返回点什么，不然会返回404错误，然后ajax的success无法执行
    }
}

控制台打印内容：

User{id=1, username=’crazykid’, password=’123456’, level=1, avatar=’default.jpg’}

返回JSON

@ResponseBody 注解可以将对象信息转为 Json 数据输出给浏览器。

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@Controller
public class ResponseBodyTest {
    @RequestMapping("responsebody")
    @ResponseBody
    public User ResponseBody() {
        User user = new User(1,"aaa","123",0,null);
        return user;
    }
}

直接用浏览器访问 http://localhost:8080/SpringMVC/responsebody.do 已经可以看到 json 信息了：

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{"id":1,"username":"aaa","password":"123","level":0,"avatar":null}

然后尝试在前台利用 ajax 获取 json 信息并显示在页面上：

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<script type="application/javascript" src="js/jquery-3.3.1.min.js"></script>

    id:<span id="id"></span><br />
    username: <span id="username"></span><br />
    password: <span id="password"></span><br />
    level: <span id="level"></span><br />
    avatar: <span id="avatar"></span><br />
    <a href="javascript:void(0)" id="getdata">点我获取数据</a>

    <script type="application/javascript">
        $(function () {
            $("#getdata").click(function(){
                $.getJSON("${pageContext.request.contextPath}/responsebody.do", function(data) {
                    $.each( data, function( key, val ) {
                        $("#"+key).text(val);
                    });
                });
            })
        })
    </script>

运行结果：

id:1
username: aaa
password: 123
level: 0
avatar:

也可以使用注解 @RestController， 它是 @ResponseBody + @Controller 的结合，如下：

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@RestController
public class RestControllerTest {
    @RequestMapping(value="/restcontroller")
    public User getUserName(){
        User user = new User(1, "crazykid", "123456", 0, null);
        return user;
    }
}

一样也是可以把对象转换成 json 数据输出的。