SpringMVC4零配置--web.xml

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Spring

servlet3.0+规范后，允许servlet，filter，listener不必声明在web.xml中，而是以硬编码的方式存在，实现容器的零配置。

ServletContainerInitializer：启动容器时负责加载相关配置

package javax.servlet;
import java.util.Set;
public interface ServletContainerInitializer {
 public void onStartup(Set<Class<?>> c, ServletContext ctx)
        throws ServletException; 
}

容器启动时会自动扫描当前服务中ServletContainerInitializer的实现类，并调用其onStartup方法，其参数Set<Class<?>> c，可通过在实现类上声明注解javax.servlet.annotation.HandlesTypes(xxx.class)注解自动注入，@HandlesTypes会自动扫描项目中所有的xxx.class的实现类，并将其全部注入Set。

Spring为其提供了一个实现类：

SpringServletContainerInitializer

package org.springframework.web;
import java.lang.reflect.Modifier;
import java.util.LinkedList;
import java.util.List;
import java.util.ServiceLoader;
import java.util.Set;
import javax.servlet.ServletContainerInitializer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.HandlesTypes;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {
        @Override
	public void onStartup(Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
			throws ServletException {

		List<WebApplicationInitializer> initializers = new LinkedList<WebApplicationInitializer>();

		if (webAppInitializerClasses != null) {
			for (Class<?> waiClass : webAppInitializerClasses) {
				// Be defensive: Some servlet containers provide us with invalid classes,
				// no matter what @HandlesTypes says...
				if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
						WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
					try {
						initializers.add((WebApplicationInitializer) waiClass.newInstance());
					}
					catch (Throwable ex) {
						throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
					}
				}
			}
		}

		if (initializers.isEmpty()) {
			servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
			return;
		}

		AnnotationAwareOrderComparator.sort(initializers);
		servletContext.log("Spring WebApplicationInitializers detected on classpath: " + initializers);

		for (WebApplicationInitializer initializer : initializers) {
			initializer.onStartup(servletContext);
		}
	}

}

从中可以看出，WebApplicationInitializer才是我们需要关心的接口，我们只需要将相应的servlet，filter，listener等硬编码到该接口的实现类中即可。比如：

xml配置：

        <!-- Log4jConfigListener -->
        <context-param>
		<param-name>log4jConfigLocation</param-name>
		<param-value>classpath:config/properties/log4j.properties</param-value>
        </context-param>
        <listener>
		<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
        </listener>

        <!-- OpenSessionInViewFilter -->
        <filter>
		<filter-name>hibernateFilter</filter-name>
		<filter-class>
			org.springframework.orm.hibernate4.support.OpenSessionInViewFilter
		</filter-class>		
        </filter>
        <filter-mapping>
		<filter-name>hibernateFilter</filter-name>
		<url-pattern>/*</url-pattern>
        </filter-mapping>

        <!-- DemoServlet -->
        <servlet>
		<servlet-name>demoServlet</servlet-name>
		<servlet-class>web.function.servlet.DemoServlet</servlet-class>
		<load-on-startup>2</load-on-startup>
        </servlet>
	<servlet-mapping>
		<servlet-name>demoServlet</servlet-name>
		<url-pattern>/demo_servlet</url-pattern>
	</servlet-mapping>

编码配置：

@Order(1)
public class CommonInitializer implements WebApplicationInitializer{

	@Override
	public void onStartup(ServletContext servletContext)
			throws ServletException {
		
		//Log4jConfigListener
		servletContext.setInitParameter("log4jConfigLocation", "classpath:config/properties/log4j.properties");
		servletContext.addListener(Log4jConfigListener.class);
		
		
		//OpenSessionInViewFilter
		OpenSessionInViewFilter hibernateSessionInViewFilter = new OpenSessionInViewFilter();
		FilterRegistration.Dynamic filterRegistration = servletContext.addFilter(
				"hibernateFilter", hibernateSessionInViewFilter);
		filterRegistration.addMappingForUrlPatterns(
				EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.INCLUDE), false, "/");
		
		
		//DemoServlet
		DemoServlet demoServlet = new DemoServlet();
		ServletRegistration.Dynamic dynamic = servletContext.addServlet(
				"demoServlet", demoServlet);
		dynamic.setLoadOnStartup(2);
		dynamic.addMapping("/demo_servlet");
				
		
	}

	
}

Spring为我们提供了一些WebApplicationInitializer的抽象类，我们只需要继承并按需修改即可，比如：

1）org.springframework.security.web.context.AbstractSecurityWebApplicationInitializer ： SpringSecurity相关配置

xml配置：

        <listener>
		<listener-class>org.springframework.security.web.session.HttpSessionEventPublisher</listener-class>
	</listener>

        <filter>
		<filter-name>springSecurityFilterChain</filter-name>
		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
	</filter>

        <filter-mapping>
		<filter-name>springSecurityFilterChain</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

编码配置：

@Order(2)
public class WebAppSecurityInitializer  extends AbstractSecurityWebApplicationInitializer 
{
	//servletContext.addListener("org.springframework.security.web.session.HttpSessionEventPublisher");
	//session监听器
	@Override
	protected boolean enableHttpSessionEventPublisher() {
        return true;
    }
}

2）org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer：MVC相关配置，比如加载spring配置文件，声明DispatcherServlet等等，参看下面的对比：

xml配置：

        <context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>
		classpath:config/context/applicationContext-AppConfig.xml,
		classpath:config/context/applicationContext-SpringSecurityConfig.xml
	        </param-value>
	</context-param>

        <listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

        <filter>
		<filter-name>Set Character Encoding</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>Set Character Encoding</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

        <servlet>
		<servlet-name>webmvc</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:config/context/applicationContext-MvcConfig.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>webmvc</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

编码方式：

@Order(3)
//spring DispatcherServlet的配置,其它servlet和监听器等需要额外声明，用@Order注解设定启动顺序
public class WebInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    /*
	  * DispatcherServlet的映射路径
	  */
    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"};
    }
 
    /*
	  * 应用上下文，除web部分
	  */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    @Override
    protected Class[] getRootConfigClasses() {
        //加载配置文件类，这里与上面的xml配置是对应的，需要使用@Configuration注解进行标注，稍后介绍
        return new Class[] {AppConfig.class, SpringSecurityConfig.class};
    }
 
    /*
	  * web上下文
	  */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    @Override
    protected Class[] getServletConfigClasses() {
        return new Class[] {MvcConfig.class};
    }
 
    /*
	  * 注册过滤器，映射路径与DispatcherServlet一致，路径不一致的过滤器需要注册到另外的WebApplicationInitializer中
	  */
    @Override
    protected Filter[] getServletFilters() {
        CharacterEncodingFilter characterEncodingFilter = new CharacterEncodingFilter();
        characterEncodingFilter.setEncoding("UTF-8");
        characterEncodingFilter.setForceEncoding(true);
        return new Filter[] {characterEncodingFilter};
    } 	

}

SpringMVC4零配置：代码下载

2014-09-10 18:21
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1 楼 ixin0877 2015-05-30

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