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:

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");

    }

}

巴特西

Spring注解开发系列VIII --- SpringMVC

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