Spring MVC实操

从配置文件开始

src/main/webapp/WEB-INF/web.xml

<!-- 
	Maven自动生成使用的2.3版本的标准，该标准默认会将jsp页面的el表达式${variable}语言关闭
-->
<!--
<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >
-->
<?xml verrsion="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
		http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
		
  <display-name>Spring MVC DEMO</display-name>
  
  <!-- Spring应用上下文，理解层次化的ApplicationContext -->
  <context-param>
  	<param-name>contextConfigLocation</param-name>
  	<param-value>/WEB-INF/configs/spring/applicationContext*.xml</param-value>
  </context-param>
  
  <listener>
  	<listener-class>
  		org.springframework.web.context.ContextLoaderListener
  	</listener-class>
  </listener>
  
  <!-- DispatcherServlet, Spring MVC的核心 -->
  <servlet>
  	<servlet-name>mvc-dispatcher</servlet-name>
  	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  	<!-- DispatcherServlet对应的上下文配置，默认为/WEB-INF/$servlet-name$-servlet.xml -->
  	<!-- 以下配置，改变默认参数 -->
  	<init-param>
  		<param-name>contextConfigLocation</param-name>
  		<param-value>/WEB-INF/configs/spring/mvc-dispatcher-servlet.xml</param-value>
  	</init-param>
  	<load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>mvc-dispatcher</servlet-name>
  	<!-- mvc-dispatcher拦截所有的请求  -->
  	<url-pattern>/</url-pattern>
  </servlet-mapping>
  
</web-app>

Spring MVC的上下文层级

src/main/webapp/WEB-INF/configs/spring/mvc-dispatcher-servlet.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"
   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">
   	
   	<!-- 本配置文件是工名为mvc-dispatcher的DispatcherServlet使用，提供其相关的Spring MVC配置 -->
   	
	<!-- 启用Spring基于annotation的DI，使用户可以在Spring MVC中使用Spring的强大功能。
		激活 @Required @Autowired,JSR 250's @PostConstruct, @PreDestroy and @Resource等标注 
	-->
	<context:annotation-config/>
	
	<!-- DispatcherServlet上下文，只管理@Controller类型的bean，忽略其他类型的bean，如@Service -->
	<context:component-scan base-package="com.test.mvcdemo">
		<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
	</context:component-scan>
	
	<!-- HandlerMapping，无需配置，Spring MVC可以默认启动。即默认会启动：
		DefaultAnnotationHandlerMapping annotation-driven HandlerMapping
	-->

	<!-- 扩充了注解驱动，可以将请求参数绑定到控制器参数
		Url中的查询参数，可以直接映射到Controller中某个输入方法的参数
	 -->
	<mvc:annotation-driven/>
	
	<!-- 静态资源处理，css、js、images -->
	<mvc:resources mapping="/resources/**" location="/resources/"/>
	
	<!-- 配置ViewResolver
		可以用多个ViewResolver
		使用order属性排序
		InternalResourceViewResolve放在最后
	-->
	<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
		<property name="prefix" value="/WEB-INF/jsps/"/>
		<property name="suffix" value=".jsp"/>
	</bean>
	
</beans>

3中不同形式编写Controller类

package com.test.mvcdemo.controller;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.test.mvcdemo.model.Course;
import com.test.mvcdemo.service.CourseService;

@Controller
@RequestMapping("/courses")
// /courses/*
public class CourseController {
  
  private static Logger log = LoggerFactory.getLogger(CourseController.class);
  
  private CourseService courseService;
  
  @Autowired
  public void setCourseServiceImpl(CourseService courseService) {
    this.courseService = courseService;
  }
  
  // 本方法仅处理 /course/view?courseId=123
  @RequestMapping(value="/view", method=RequestMethod.GET)
  public String viewCourse(@RequestParam("courseId") Integer courseId, Model model) {
    
    log.debug("In viewCourse, courseId = {}", courseId);
    
    Course course = courseService.getCourseById(courseId);
    model.addAttribute(course);
    // 返回jsp的文件名
    return "course-overview";
  }
  
  // /courses/view2/{courseId}
  @RequestMapping(value="/view2/{courseId}", method=RequestMethod.GET)
  public String viewCourse2(@PathVariable("courseId") Integer courseId, Map<String, Object> model) {
    log.debug("In viewCourse2, courseId = {}", courseId);
    Course course = courseService.getCourseById(courseId);
    model.put("course", course);
    return "course-overview";
  }
  
  // /course/view?courseId=333
  @RequestMapping("view3")
  public String viewCourse3(HttpServletRequest request) {
    Integer courseId = Integer.valueOf(request.getParameter("courseId"));
    Course course = courseService.getCourseById(courseId);
    request.setAttribute("course", course);
    return "course-overview";
  }
}

总结

通过@Controller声明一个Controller

通过@RequestMapping 映射URL和方法，通常出现在我们的类级别和方法级别，二者组合完成了对URL映射请求的拦截 :::

通过URL template(@RequestParam and @PathVariable)将URL中的参数，绑定到Controller中method的入参 :::

同时也可以通过HTTPServletRequest and/or HttpSession等对象来获取我们想要的结果 :::

Binding 数据绑定

将请求中的字段按照名字匹配的原则填入模型对象。

// CourseController.java

  @RequestMapping(value="/admin", method=RequestMethod.GET, params="add")
  public String createCourse() {
    return "admin/edit";
  }
  
  // 接收处理表单数据
  @RequestMapping(value="/save", method=RequestMethod.POST)
//  public String doSave(Course course) {
  public String doSave(@ModelAttribute Course course) {
    
    log.debug("Info of Course");
    log.debug(ReflectionToStringBuilder.toString(course));
    
    System.out.println(course.toString());
    
    // 在此进行业务操作，比如数据库持久化
    course.setCourseId(555);
    return "redirect:view2/" + course.getCourseId();
  }

总结

在Controller参数上，使用@ModelAttribute实现模型与页面数据的绑定，及如果在MVC中使用重定向或转发redirect/forward

FileUpload 单文件上传

src/main/webapp/WEB-INF/configs/spring/mvc-dispatcher-servlet.xml

<!-- 上传文件解析配置 -->
<!-- 200 * 1024 * 1024 即200M，resolveLazily属性启用是为了推迟文件解析，以便捕获文件大小异常 -->
<!-- 依赖org.apache.commons.fileupload包，所以在pom.xml中引入commons-fileupload -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="209715200"/>
    <property name="defaultEncoding" value="UTF-8"/>
    <property name="resolveLazily" value="true"/>
</bean>

/pom.xml

    <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
	<dependency>
	    <groupId>commons-fileupload</groupId>
	    <artifactId>commons-fileupload</artifactId>
	    <version>1.3.3</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
	<dependency>
	    <groupId>commons-io</groupId>
	    <artifactId>commons-io</artifactId>
	    <version>2.6</version>
	</dependency>

admin/file.jsp

<form action="<%=request.getContextPath() %>/courses/do-upload" method="post" enctype="multipart/form-data">
    <h1 class="course-title">文件上传</h1>
    <div>
        <input type="file" name="file">
    </div>
    <button type="submit">上传</button>
</form>

Controller.java

  @RequestMapping(value="/upload", method=RequestMethod.GET)
  public String showUploadPage() {
    return "admin/file";
  }
  
  @RequestMapping(value="/do-upload", method=RequestMethod.POST)
  public String doUploadFile(@RequestParam("file") MultipartFile file) throws IOException {
    
    if (!file.isEmpty()) {
      FileUtils.copyInputStreamToFile(file.getInputStream(), new File("D:/java/temp", System.currentTimeMillis() + "_" + file.getOriginalFilename()));
    }
    
    return "home";
  }

JSON

JSON (JavaScript Object Notation) is a lightweight data-interchange format

相同数据，不同呈现方式。JSPView, JsonView

ContentNegotiatingViewResolver

配置文件：src/main/webapp/WEB-INF/configs/spring/mvc-dispatcher-servlet.xml

<!-- 配置ViewResolver。可以用多个ViewResolver。使用order属性排序。InternalResourceViewResolver放在最后。 -->
<!-- 该配置可以让MVC将相同的数据，呈现成不同的形式 -->
<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
    <property name="order" value="1"/>
    <property name="mediaTypes">
        <map>
            <entry key="json" value="application/json"/>
            <entry key="xml" value="application/xml"/>
            <entry key="htm" value="text/html"/>
        </map>
    </property>
    
    <property name="defaultViews">
        <list>
            <!-- JSON View -->
            <bean class="org.springframework.web.servlet.view.json.MappingJackson2JsonView"></bean>
        </list>
    </property>
    <property name="ignoreAcceptHeader" value="true"/>
</bean>

添加依赖：/pom.xml

<properties>
  	<jackson.version>2.9.9.1</jackson.version>
</properties>
  
<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>${jackson.version}</version>
</dependency>

src/main/java/com/test/mvcdemo/controller/CourseController.java

  @RequestMapping(value="/{courseId}", method=RequestMethod.GET)
  public @ResponseBody Course getCourseInJson(@PathVariable Integer courseId) {
    return courseService.getCourseById(courseId);
  }
  
  @RequestMapping(value="/json/{courseId}", method=RequestMethod.GET)
  public ResponseEntity<Course> getCourseInJson2(@PathVariable Integer courseId) {
    Course course = courseService.getCourseById(courseId);
    return new ResponseEntity<Course>(course, HttpStatus.OK);
  }

总结

Work with JSON

ContentNegotiatingViewResolver

ResponseEntity

@ResponseBody/@RequestBody

@RequestBody的使用 (opens new window)

Details

源码

codes/spring-mvc-demo1

扩展阅读

@RequestBody的使用 https://blog.csdn.net/justry_deng/article/details/80972817