Spring注解开发系列VIII --- SpringMVC

SpringMVC是三层架构中的控制层部分，有过JavaWEB开发经验的同学一定很熟悉它的使用了。这边有我之前整理的SpringMVC相关的链接:

1.SpringMVC入门

2.SpringMVC进阶

3.深入SpringMVC注解

看过之后大致对springmvc有一个了解，但对于真正完全掌握springmvc还差得远，本篇博客主要针对的是springmvc的注解开发，传统的项目使用spingmvc避免不了地需要在web.xml里配置前端控制器等等，想要在项目中优雅地去掉这些配置，还得学习如何使用万能的注解来代替这些配置。

Servlet3.0整合SpringMVC

一.原理分析

1) 首先需要导入pom依赖gav:

 <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>4.3.11.RELEASE</version>
</dependency>

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.0.1</version>
    <scope>provided</scope>
</dependency>

2) web容器启动

1.web容器启动的时候会扫描每个jar包下的META-INF/services/javax.servlet.ServletContainerInitializer文件

2.加载这个文件指定类的org.springframework.web.SpringServletContainerInitializer

3.Spring的应用一启动会加载感兴趣的WebApplicationInitializer接口下的所有组件

4.并且为WebApplicationInitializer组件创建对象(非接口、非抽象类)

@HandlesTypes({WebApplicationInitializer.class})
public class SpringServletContainerInitializer implements ServletContainerInitializer {
    public SpringServletContainerInitializer() {
    }

    public void onStartup(Set<Class<?>> webAppInitializerClasses, ServletContext servletContext) throws ServletException {
        List<WebApplicationInitializer> initializers = new LinkedList();
        Iterator var4;
        if (webAppInitializerClasses != null) {
            var4 = webAppInitializerClasses.iterator();

            while(var4.hasNext()) {
                Class<?> waiClass = (Class)var4.next();
                if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) && WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
                    try {
                        initializers.add((WebApplicationInitializer)waiClass.newInstance());
                    } catch (Throwable var7) {
                        throw new ServletException("Failed to instantiate WebApplicationInitializer class", var7);
                    }
                }
            }
        }

        if (initializers.isEmpty()) {
            servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
        } else {
            servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
            AnnotationAwareOrderComparator.sort(initializers);
            var4 = initializers.iterator();

            while(var4.hasNext()) {
                WebApplicationInitializer initializer = (WebApplicationInitializer)var4.next();
                initializer.onStartup(servletContext);
            }

        }
    }
}

 5.WebApplicationInitializer的子类

AbstractContextLoaderInitializer:创建根容器,createRootApplicationContext();

AbstractDispatcherServletInitializer:

创建一个web的ioc容器,createServletApplicationContext();

创建了DispacherServlet:createDispacherServlet();

将创建的DispacherServlet添加到ServletContext中

AbstractAnnotationConfigDispatcherServletInitializer：注解方式配置的DispacherServlet初始化器

创建根容器createRootApplicationContext()

创建一个webioc容器createServletApplicationContext()

总结:要以注解方式来启动SpringMVC,实现配置类的方式,需要继承AbstractAnnotationConfigDispatcherServletInitializer,实现抽象方法指定的DispacherServlet的配置信息。　　

二.整合SpringMVC

经过上述分析，我们来试着整合SpringMVC。

1.创建一个类来继承AbstractAnnotationConfigDispatcherServletInitializer

//在web容器启动的时候创建对象,调用方法来初始化容器以及前端控制器
public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    /**
     * 获取根容器的配置(类似于之前监听器配置spring的配置文件)
     *    <listener>
     *      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
     *     </listener>
     *
     *<context-param>
     *     <param-name>contextConfigLocation</param-name>
     *     <param-value>classpath:spring/applicationContext-*.xml</param-value> 。
     * </context-param>
     *
     *
     *
     **/

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class[]{RootConig.class};
    }

    /**
     * 获取web容器的配置类(类似于springmvc的配置文件)(前端控制器)子容器
     * @return
     */
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{AppConfig.class};
    }

    /**
     * 获取DispatcherServlet的映射信息
     *
     * {"/"}:拦截所有请求包括静态资源(xx.js,xx.png),不包括*.jsp
     * {"/*"}:拦截所有请求，包括*.jsp,jsp页面是tomcat的jsp引擎解析的
     * @return
     */
    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
}

2.创建根容器的配置

//Spring的容器不扫描Controller,交给SpringMvc扫描
@ComponentScan(value = "com.wang",excludeFilters =
        {@ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})})
public class RootConig {
}

3.创建web容器的配置类

//SpringMVC只扫描Controller,子容器
//useDefaultFilters=false 禁用默认的过滤规则
@ComponentScan(value = "com.wang",includeFilters =
        {@ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})},useDefaultFilters = false)
public class AppConfig {
}

4.将配置类加入到AbstractAnnotationConfigDispatcherServletInitializer的子类中

5.创建Controller，Service类测试

@Controller
public class HelloController {
    @Autowired
    private MyHelloService myHelloService;
    @ResponseBody
    @RequestMapping("/myhello")
    public String hello(){
        return myHelloService.sayHello();
    }
}

@Service
public class MyHelloService {
    public String sayHello(){
        return "hello";
    }
}

启动应用，访问"/myhello"请求，若能正常访问到该请求，说明上述配置类生效。

三.定制SpringMVC

1). @EnableWebMVC:开启SpringMVC定制配置功能相当于<mvc:annotation-driven/>

2).  配置组件(视图解析器、视图映射、静态资源映射、拦截器)

@ComponentScan(value = "com.wang",includeFilters =
        {@ComponentScan.Filter(type = FilterType.ANNOTATION,classes = {Controller.class})},useDefaultFilters = false)
@EnableWebMvc
public class AppConfig extends WebMvcConfigurerAdapter {
    /**
     * 路径映射规则
     * @param pathMatchConfigurer
     */
    @Override
    public void configurePathMatch(PathMatchConfigurer pathMatchConfigurer) {

    }

    /**
     * 视图解析器
     * @param registry
     */
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        //默认所有的页面都从"/WEB-INF/*.jsp"
        //registry.jsp();
        registry.jsp("/WEB-INF/views/",".jsp");
    }

    /**
     * 配置静态资源访问,将springmvc处理不了的请求交给springmvc,开启后可以访问静态资源(*.js,*.jpg,...)
     * @param defaultServletHandlerConfigurer
     */
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer defaultServletHandlerConfigurer) {
        defaultServletHandlerConfigurer.enable();//相当于开启了default-servlet-handler  <mvc:default-servlet-handler/>
    }

    /**
     * 添加拦截器
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
       registry.addInterceptor(new MyInterceptor()).addPathPatterns("/success");
    }
}