第4章 Spring MVC 4.x

作者: 意大利大炮 | 来源:发表于2018-12-06 21:40 被阅读0次

4.1 Spring MVC概述

Spring MVC是Spring中的一个用于web开发的模块
MVC：Model + View + Controller（数据模型 + 视图 + 控制器）
三层架构：Presentation tier + Application tier + Data tier (展现层 + 应用层 + 数据访问层)
MVC与三层架构的关系：MVC只存在于三层架构的展现层
1. M实际上是数据模型，是包含数据的对象，在Spring MVC例有一个专门的类叫Model，用来和V之间的数据交互。传值
2. V指的是视图页面，包含JSP、freeMarker、Velocity、Thymeleaf、Tile等。
3. C就是控制器了（Spring MVC中注解@Controller的类）

4.2 Spring MVC项目快速搭建

4.2.1 构建maven项目

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.spring</groupId>
    <artifactId>springmvcDemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <jsp.verion>2.2</jsp.verion>
        <jstl.version>1.2</jstl.version>
        <servlet.version>3.1.0</servlet.version>

        <!-- spring -->
        <spring-framework.version>4.1.5.RELEASE</spring-framework.version>

        <!-- logging -->
        <logback.version>1.0.13</logback.version>
        <slf4j.version>1.7.5</slf4j.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>


        <!-- 其他web依赖 -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>${jstl.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>${servlet.version}</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>${jsp.verion}</version>
            <scope>provided</scope>
        </dependency>

        <!-- spring and Transactions -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>

        <!-- 使用slf4J 和 LogBack作为日志 -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.16</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>${slf4j.version}</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>${logback.version}</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>${logback.version}</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-access</artifactId>
            <version>${logback.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.3</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

4.2.2 日志配置

<?xml version="1.0" encoding="UTF-8" ?>
<configuration scan="true" scanPeriod="1 seconds">
    <contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator">
        <resetJUL>true</resetJUL>
    </contextListener>

    <jmxConfigurator/>

    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>logback: %d{HH:mm:ss.SSS} %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <logger name="org.springframework.web" level="DEBUG"/>
    <root level="info">
        <appender-ref ref="console"/>
    </root>
</configuration>

4.2.3 演示页面

在src/main.resource建立views目录，并建立index.jsp（resource下防止页面是spring boot的放置方式）

<%@page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>Insert title here</title>
</head>
<body>
    <pre>
        Welcome to Spring MVC world
    </pre>
</body>
</html>

4.2.4 SpringMVC配置

使用配置类配置一个JSP的ViewResolver，用来映射路径和实际页面的位置
@EnableWebMvc注解会开启一些默认配置，如一些ViewResolve或者MessageConverter等等

@Configuration
@EnableWebMvc
@ComponentScan("com.springmvcDemo")
public class MyMvcConfig {
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
        viewResolver.setPrefix("/WEB-INF/classes/views/");
        viewResolver.setSuffix(".jsp");
        viewResolver.setViewClass(JstlView.class);
        return viewResolver;
    }
}

4.2.5 Web配置

创建一个集成了WebApplicationInitializer接口的类，实现此接口可以自动的呗SpringServletContainerInitializer(用来启动Servlet3.0的容器)获取到

public class WebInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext servletContext) {
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
        // 注册
        ctx.register(MyMvcConfig.class);
        // 关联
        ctx.setServletContext(servletContext);

        ServletRegistration.Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(ctx));
        servlet.addMapping("/");
        servlet.setLoadOnStartup(1);
    }
}

4.2.6 简单控制器

@Controller
public class HelloController {

    @RequestMapping("/index")
    public String hello() {
        return "index";
    }
}

4.2.7 运行

程序部署到Tomcat，启动tomcat后，访问控制器的地址
不知道为什么这里没能启动成功，需要再多次测试

4.3 Spring MVC 的常用注解

4.3.1 常用注解

@Controller
@RequestMappering
@ResponseBody: 防止返回结果被解析为页面
@RequestBody
@PathVariable
@RestController

4.3.2 使用示例

添加jackson以及相关依赖，获得对象和json或xml之间的转换
正常开发中，很少用到xml，一般使用json，因为json比xml简洁，但这里演示同时支持json和xml的maven与只支持json的maven
同时支持xml和json的依赖

<dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-xml</artifactId>
            <version>2.5.3</version>
        </dependency>

只纯支持json的依赖

  <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.5.3</version>
        </dependency>

创建一个对象，用于演示获取request对象参数和返回此对象到response
jackson对对象和json做转换时，一定需要一个空的构造方法？？？

public class DemoObj {
    private Long id;
    private String name;
    public DemoObj() {
        super();
    }
    public DemoObj(Long id, String name) {
        this.id = id;
        this.name = name;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

创建演示控制器

@Controller   // 表明是一个控制器
@RequestMapping("/anno")  // 映射此类的访问路径
public class DemoAnnoContraoller {

    @RequestMapping(produces = "text/plain;charset=UTF-8")   // 未设置路径，所以使用类级别的路径；produces可指定返回的response的媒体类型和字符集
    public @ResponseBody String index(HttpServletRequest request) {  // 演示可接收HttpServletRequest作为参数
        return "url:" + request.getRequestURL() + "can access";
    }

    @RequestMapping(value = "/pathvar/{str}", produces = "text/plain;charset=UTF-8")  // 演示可接收路径参数，并在方法参数前结合@PathVariable使用
    public @ResponseBody String demoPathVar(@PathVariable String str, HttpServletRequest request) {
        return "url:" + request.getRequestURL() + "can access, str" + str;
    }

    @RequestMapping(value = "/requestParam/", produces = "text/plain;charset=UTF-8")  // 演示常规的request参数获取，访问路径为/anno/requestParam?id=1
    public @ResponseBody String passRequestParam(Long id, HttpServletRequest request) {
        return "url:" + request.getRequestURL() + "can access, id" + id;
    }

    @RequestMapping(value = "/obj", produces = "application/json;charset=UTF-8") // 演示直接解释参数到对象，访问路径为/anno/obj?id=1&name=xx
    @ResponseBody       // 演示@ResponseBody注解可以用到方法上
    public String passObj(DemoObj obj, HttpServletRequest request) {
        return "url:" + request.getRequestURL() + "can access, obj id" + obj.getId() + " obj name: " + obj.getName();
    }

    @RequestMapping(value = {"/name1", "/name2"}, produces = "text/plain;charset=UTF-8")  // 演示映射不同的路径到相同的方法上，访问路径为/anno/name1或/anno/name2
    public @ResponseBody String remove(HttpServletRequest request) {
        return "url:" + request.getRequestURL() + "can access";
    }
}

演示rest方式的控制器

@RestController
@RequestMapping("/rest")
public class DemoRestController {

    // 演示返回对象自动解析为json
    @RequestMapping(value = "/getJson", produces = "application/json;charset=UTF-8")
    public DemoObj getJson(DemoObj obj) {
        return new DemoObj(obj.getId() + 1, obj.getName() + "yy");
    }

    // 演示返回对象为xml
    @RequestMapping(value = "/getJson", produces = "application/xml;charset=UTF-8")
    public DemoObj getXml(DemoObj obj) {
        return new DemoObj(obj.getId() + 1, obj.getName() + "yy");
    }
}

4.4 Spring MVC的基本配置

Spring MVC的定制配置需要我们的配置类继承一个WebMvcConfigurerAdapter类，并在此类使用@EnableWebMvc注解，来开启对Spring MVC的配置支持，这样就可以重写这个类的方法，完成常用的配置
WebMvcConfigurerAdapter类是WebMvcConfigurer接口的实现，所以WebMvcConfigurer的API内的方法也可以用来配置MVC。下面展示一下这两个类的源码：
WebMvcConfigurerAdapter：

public abstract class WebMvcConfigurerAdapter implements WebMvcConfigurer {
    public WebMvcConfigurerAdapter() {
    }
    public void addFormatters(FormatterRegistry registry) {
    }
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    }
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
    }
    public Validator getValidator() {
        return null;
    }
    public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
    }
    public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
    }
    public void configurePathMatch(PathMatchConfigurer configurer) {
    }
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
    }
    public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {
    }
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
    }
    public MessageCodesResolver getMessageCodesResolver() {
        return null;
    }
    public void addInterceptors(InterceptorRegistry registry) {
    }
    public void addViewControllers(ViewControllerRegistry registry) {
    }
    public void configureViewResolvers(ViewResolverRegistry registry) {
    }
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
    }
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    }
}

WebMvcConfigurer：


public interface WebMvcConfigurer {
    void addFormatters(FormatterRegistry var1);

    void configureMessageConverters(List<HttpMessageConverter<?>> var1);

    void extendMessageConverters(List<HttpMessageConverter<?>> var1);

    Validator getValidator();

    void configureContentNegotiation(ContentNegotiationConfigurer var1);

    void configureAsyncSupport(AsyncSupportConfigurer var1);

    void configurePathMatch(PathMatchConfigurer var1);

    void addArgumentResolvers(List<HandlerMethodArgumentResolver> var1);

    void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> var1);

    void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> var1);
    // 注册拦截器
    void addInterceptors(InterceptorRegistry var1);

    MessageCodesResolver getMessageCodesResolver();
    // 无任何事务处理，只是简单页面转向的简化配置
    void addViewControllers(ViewControllerRegistry var1);

    void configureViewResolvers(ViewResolverRegistry var1);
    // 增加静态文件映射
    void addResourceHandlers(ResourceHandlerRegistry var1);

    void configureDefaultServletHandling(DefaultServletHandlerConfigurer var1);
}

4.4.1 静态资源映射

程序的静态文件（js、css、图片）等需要直接访问，这时我们可以重写addResourceHandlers来实现


/**
 * 测试，静态资源映射
 */
@Configuration
@EnableWebMvc
@ComponentScan("com.springmvcDemo.resource_handlers")
public class MyMvcConfig extends WebMvcConfigurerAdapter {
    
    // 类似于xml的<mvc: resource />的静态资源映射配置
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        // 指定目录下的本地文件映射为一个url，使得可以直接访问
        registry.addResourceHandler("/views/**").addResourceLocations("classpath:/views/");
    }
}

4.4.2 拦截器配置

让Bean实现HanlderInterceptor接口或者继承HandlerInterceptorAdapter类来实现拦截器
通过重写WebMvcConfigurerAdapter 的addInterceptors方法来注册自定义的拦截器
实现一个拦截器：

public class DemoInterceptor implements HandlerInterceptor {
    // 请求前调用
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        httpServletRequest.setAttribute("startTime", System.currentTimeMillis());
        return true;
    }
    // 请求后调用
    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("本次请求处理时间为：" + (System.currentTimeMillis() - (long) httpServletRequest.getAttribute("startTime")));
    }
    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
    }
}

注册拦截器到配置Bean：

    @Bean
    public DemoInterceptor demoInterceptor() {
        return new DemoInterceptor();
    }
    // 注册拦截器
    @Autowired 
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(demoInterceptor());
    }

4.4.3 @ControllerAdvice（建言）

通过@ControllerAdvice注解，可以将控制器的全局配置放到一个位置，注解了@Controller的类的方法可以使用@ExeptionHandler、@InitBinder、@ModelAttribute注解到方法上，这对所有注解了@RequestMapping的控制器内方法有效
@ExceptionHandler：用于全局处理控制器内的异常
@InitBinder：用啦设置WebDataBinder，用来自动绑定一个前台请求参数到Model中
@ModelAttribute：绑定键值到Model内，让全聚德@RequestMapping可以获得在此处设置的键值对
创建建言类

@ControllerAdvice //生命一个控制器建言，此注解组合了@Component注解
public class DemoHandlerAdvice {
    // 定义全局异常处理，拦截所有的Exception
    @ExceptionHandler(value = Exception.class)
    public ModelAndView exception(Exception exception, WebRequest request) {
        ModelAndView modelAndView = new ModelAndView("error");
        modelAndView.addObject("errorMsg", exception.getMessage());
        return modelAndView;
    }
    // 将键值对添加到全局，所有注解@RequestMappering的方法都可以获得此键值对
    @ModelAttribute
    public void addAttributes(Model model) {
        model.addAttribute("msg", "额外信息");
    }
    // 定制WebDataBinder
    @InitBinder
    public void initBinder(WebDataBinder webDataBinder) {
        webDataBinder.setDisallowedFields("id"); // 这里过滤掉了Id，即后台无法获取到该字段
    }
}

创建演示的控制器

@Controller
public class AdviceController {
    @RequestMapping("/advice")
    public String getSomething(@ModelAttribute("msg") String msg, DemoObj demoObj) { // 这里接收msg和demoObj，但demoObj中的id无法获取到了
        throw new IllegalArgumentException("非常抱歉，参数有误");
    }
}

4.4.4 其他配置

ViewController
正常的页面转向代码：

// 演示简单页面转向
    @RequestMapping("/index")
    public String hello() {
        return "index";
    }

通过重写addViewController方法来简化：

    @Autowired
    // 配置页面转向
    public void addViewControllers(ViewControllerRegistry registry) {
        registry.addViewController("index").setViewName("index");
    }

第4章 Spring MVC 4.x

4.1 Spring MVC概述

4.2 Spring MVC项目快速搭建

4.2.1 构建maven项目

4.2.2 日志配置

4.2.3 演示页面

4.2.4 SpringMVC配置

4.2.5 Web配置

4.2.6 简单控制器

4.2.7 运行

4.3 Spring MVC 的常用注解

4.3.1 常用注解

4.3.2 使用示例

4.4 Spring MVC的基本配置

4.4.1 静态资源映射

4.4.2 拦截器配置

4.4.3 @ControllerAdvice（建言）

4.4.4 其他配置

4.5 Spring MVC的高级配置

4.5.1 文件上传配置

4.5.2 自定义HttpMessageConverter

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