【Java Web开发学习】Spring MVC 开始配置

Spring MVC 开始配置

转载：http://www.cnblogs.com/yangchongxing/p/8871370.htm

学习搭建最简单的Spring MVC框架。

===============================================================l

Java配置方式
Xml配置方式

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Jar包下载地址：http://repo.spring.io/release/org/springframework/spring/4.3.9.RELEASE/spring-framework-4.3.9.RELEASE-dist.zip

新建动态web工程ycxfw(名字根据实际情况定)，复制下面的jar到WebContentWEB-INFlib目录

commons-logging-1.2.jar
spring-aop-4.3.9.RELEASE.jar
spring-aspects-4.3.9.RELEASE.jar
spring-beans-4.3.9.RELEASE.jar
spring-context-4.3.9.RELEASE.jar
spring-context-support-4.3.9.RELEASE.jar
spring-core-4.3.9.RELEASE.jar
spring-expression-4.3.9.RELEASE.jar
spring-instrument-4.3.9.RELEASE.jar
spring-jdbc-4.3.9.RELEASE.jar
spring-jms-4.3.9.RELEASE.jar
spring-messaging-4.3.9.RELEASE.jar
spring-orm-4.3.9.RELEASE.jar
spring-oxm-4.3.9.RELEASE.jar
spring-test-4.3.9.RELEASE.jar
spring-tx-4.3.9.RELEASE.jar
spring-web-4.3.9.RELEASE.jar
spring-webmvc-4.3.9.RELEASE.jar
spring-websocket-4.3.9.RELEASE.jar

1、基于Java配置（推荐）

借助Servlet3规范和Spring3.1，我们可以不用web.xml就能配置DispatchServlet

package cn.ycx.web.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class ServletWebApplicationInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class<?>[] {RootConfig.class}; //ContextLoaderListener上下文配置
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class<?>[] {ServletConfig.class}; //DispatcherServlet上下文配置
    }

    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"}; //将DispatcherServlet映射到 /
    }

}

package cn.ycx.web.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;

@Configuration
@ComponentScan(
        basePackages = {"cn.ycx.web"},
        // 排除掉
        excludeFilters = {@Filter( type=FilterType.ANNOTATION, value={org.springframework.stereotype.Controller.class} )} 
        )
public class RootConfig {

}

package cn.ycx.web.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.context.support.ResourceBundleMessageSource;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration
@EnableWebMvc
@ComponentScan(
        basePackages = {"cn.ycx.web.controller"},
        // 仅仅扫描
        includeFilters = {@Filter( type=FilterType.ANNOTATION, value={org.springframework.stereotype.Controller.class} )}
        )
public class ServletConfig extends WebMvcConfigurerAdapter {
    /**
     * 配置JSP视图解析器
     * @return
     */
    @Bean
    public ViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);
        return resolver;
    }
    /**
     * 配置静态文件处理
     */
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
}

新建WebContentWEB-INFviews estindex.jsp文件

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
Test page index jsp
</body>
</html>

启动tomcat服务器访问，http://127.0.0.1:8080/ycxfw/test/index。

到此代码已经写完了。

@Configuration 注解表示该bean是一个配置文件，Spring自动加载其中的bean

@EnableWebMvc 注解表示启用Spring Mvc

@ComponentScan 注解表示自动扫描要装配的bean，basePackages是要扫描的目录，默认扫描配置文件所在的包及子包；includeFilters 包含过滤，excludeFilters 排除过滤

ServletConfig配置Spring MVC相关的bean（相当于DispatcherServlet的配置），RootConfig配置spring相关的bean（相当于ContextLoaderListener的配置）

有同学可能对没有web.xml文件而疑惑，我们来说说原因。

javax.servlet.ServletContainerInitializer是Servlet 3.0 新增的一个接口类，容器在启动时使用JAR Service API来发现ServletContainerInitializer的实现类，并且容器将WEB-INF/lib目录下JAR包中的类都交给该类的onStartup()方法处理，我们通常需要在该实现类上使用 @HandlesTypes 注解来指定希望被处理的类，过滤掉不希望给 onStartup()处理的类。

* Licensed to the Apache Software Foundation (ASF) under one or more
package javax.servlet;

import java.util.Set;

/**
 * ServletContainerInitializers (SCIs) are registered via an entry in the
 * file META-INF/services/javax.servlet.ServletContainerInitializer that must be
 * included in the JAR file that contains the SCI implementation.
 * <p>
 * SCI processing is performed regardless of the setting of metadata-complete.
 * SCI processing can be controlled per JAR file via fragment ordering. If an
 * absolute ordering is defined, the only those JARs included in the ordering
 * will be processed for SCIs. To disable SCI processing completely, an empty
 * absolute ordering may be defined.
 * <p>
 * SCIs register an interest in annotations (class, method or field) and/or
 * types via the {@link javax.servlet.annotation.HandlesTypes} annotation which
 * is added to the class.
 *
 * @since Servlet 3.0
 */
public interface ServletContainerInitializer {

    /**
     * Receives notification during startup of a web application of the classes
     * within the web application that matched the criteria defined via the
     * {@link javax.servlet.annotation.HandlesTypes} annotation.
     *
     * @param c     The (possibly null) set of classes that met the specified
     *              criteria
     * @param ctx   The ServletContext of the web application in which the
     *              classes were discovered
     *
     * @throws ServletException If an error occurs
     */
    void onStartup(Set<Class<?>> c, ServletContext ctx) throws ServletException;
}

也就是说容器自动发现实现ServletContainerInitializer接口的类，如果能发现的话，就会用它来配置Servlet容器，Spring提供了这个接口的实现 SpringServletContainerInitializer

/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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;

/**
 * Servlet 3.0 {@link ServletContainerInitializer} designed to support code-based
 * configuration of the servlet container using Spring's {@link WebApplicationInitializer}
 * SPI as opposed to (or possibly in combination with) the traditional
 * {@code web.xml}-based approach.
 *
 * <h2>Mechanism of Operation</h2>
 * This class will be loaded and instantiated and have its {@link #onStartup}
 * method invoked by any Servlet 3.0-compliant container during container startup assuming
 * that the {@code spring-web} module JAR is present on the classpath. This occurs through
 * the JAR Services API {@link ServiceLoader#load(Class)} method detecting the
 * {@code spring-web} module's {@code META-INF/services/javax.servlet.ServletContainerInitializer}
 * service provider configuration file. See the
 * <a href="http://download.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#Service%20Provider">
 * JAR Services API documentation</a> as well as section <em>8.2.4</em> of the Servlet 3.0
 * Final Draft specification for complete details.
 *
 * <h3>In combination with {@code web.xml}</h3>
 * A web application can choose to limit the amount of classpath scanning the Servlet
 * container does at startup either through the {@code metadata-complete} attribute in
 * {@code web.xml}, which controls scanning for Servlet annotations or through an
 * {@code <absolute-ordering>} element also in {@code web.xml}, which controls which
 * web fragments (i.e. jars) are allowed to perform a {@code ServletContainerInitializer}
 * scan. When using this feature, the {@link SpringServletContainerInitializer}
 * can be enabled by adding "spring_web" to the list of named web fragments in
 * {@code web.xml} as follows:
 *
 * <pre class="code">
 * {@code
 * <absolute-ordering>
 *   <name>some_web_fragment</name>
 *   <name>spring_web</name>
 * </absolute-ordering>
 * }</pre>
 *
 * <h2>Relationship to Spring's {@code WebApplicationInitializer}</h2>
 * Spring's {@code WebApplicationInitializer} SPI consists of just one method:
 * {@link WebApplicationInitializer#onStartup(ServletContext)}. The signature is intentionally
 * quite similar to {@link ServletContainerInitializer#onStartup(Set, ServletContext)}:
 * simply put, {@code SpringServletContainerInitializer} is responsible for instantiating
 * and delegating the {@code ServletContext} to any user-defined
 * {@code WebApplicationInitializer} implementations. It is then the responsibility of
 * each {@code WebApplicationInitializer} to do the actual work of initializing the
 * {@code ServletContext}. The exact process of delegation is described in detail in the
 * {@link #onStartup onStartup} documentation below.
 *
 * <h2>General Notes</h2>
 * In general, this class should be viewed as <em>supporting infrastructure</em> for
 * the more important and user-facing {@code WebApplicationInitializer} SPI. Taking
 * advantage of this container initializer is also completely <em>optional</em>: while
 * it is true that this initializer will be loaded and invoked under all Servlet 3.0+
 * runtimes, it remains the user's choice whether to make any
 * {@code WebApplicationInitializer} implementations available on the classpath. If no
 * {@code WebApplicationInitializer} types are detected, this container initializer will
 * have no effect.
 *
 * <p>Note that use of this container initializer and of {@code WebApplicationInitializer}
 * is not in any way "tied" to Spring MVC other than the fact that the types are shipped
 * in the {@code spring-web} module JAR. Rather, they can be considered general-purpose
 * in their ability to facilitate convenient code-based configuration of the
 * {@code ServletContext}. In other words, any servlet, listener, or filter may be
 * registered within a {@code WebApplicationInitializer}, not just Spring MVC-specific
 * components.
 *
 * <p>This class is neither designed for extension nor intended to be extended.
 * It should be considered an internal type, with {@code WebApplicationInitializer}
 * being the public-facing SPI.
 *
 * <h2>See Also</h2>
 * See {@link WebApplicationInitializer} Javadoc for examples and detailed usage
 * recommendations.<p>
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @author Rossen Stoyanchev
 * @since 3.1
 * @see #onStartup(Set, ServletContext)
 * @see WebApplicationInitializer
 */
@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {

    /**
     * Delegate the {@code ServletContext} to any {@link WebApplicationInitializer}
     * implementations present on the application classpath.
     * <p>Because this class declares @{@code HandlesTypes(WebApplicationInitializer.class)},
     * Servlet 3.0+ containers will automatically scan the classpath for implementations
     * of Spring's {@code WebApplicationInitializer} interface and provide the set of all
     * such types to the {@code webAppInitializerClasses} parameter of this method.
     * <p>If no {@code WebApplicationInitializer} implementations are found on the classpath,
     * this method is effectively a no-op. An INFO-level log message will be issued notifying
     * the user that the {@code ServletContainerInitializer} has indeed been invoked but that
     * no {@code WebApplicationInitializer} implementations were found.
     * <p>Assuming that one or more {@code WebApplicationInitializer} types are detected,
     * they will be instantiated (and <em>sorted</em> if the @{@link
     * org.springframework.core.annotation.Order @Order} annotation is present or
     * the {@link org.springframework.core.Ordered Ordered} interface has been
     * implemented). Then the {@link WebApplicationInitializer#onStartup(ServletContext)}
     * method will be invoked on each instance, delegating the {@code ServletContext} such
     * that each instance may register and configure servlets such as Spring's
     * {@code DispatcherServlet}, listeners such as Spring's {@code ContextLoaderListener},
     * or any other Servlet API componentry such as filters.
     * @param webAppInitializerClasses all implementations of
     * {@link WebApplicationInitializer} found on the application classpath
     * @param servletContext the servlet context to be initialized
     * @see WebApplicationInitializer#onStartup(ServletContext)
     * @see AnnotationAwareOrderComparator
     */
    @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;
        }

        servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
        AnnotationAwareOrderComparator.sort(initializers);
        for (WebApplicationInitializer initializer : initializers) {
            initializer.onStartup(servletContext);
        }
    }

}

这个类又会反过来查找实现WebApplicationInitializer的类并将配置的任务交给他们来完成。

我们来看看继承关系，我们自己的类ServletWebApplicationInitializer

继承AbstractAnnotationConfigDispatcherServletInitializer继承AbstractDispatcherServletInitializer继承AbstractContextLoaderInitializer继承WebApplicationInitializer

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

/**
 * Interface to be implemented in Servlet 3.0+ environments in order to configure the
 * {@link ServletContext} programmatically -- as opposed to (or possibly in conjunction
 * with) the traditional {@code web.xml}-based approach.
 *
 * <p>Implementations of this SPI will be detected automatically by {@link
 * SpringServletContainerInitializer}, which itself is bootstrapped automatically
 * by any Servlet 3.0 container. See {@linkplain SpringServletContainerInitializer its
 * Javadoc} for details on this bootstrapping mechanism.
 *
 * <h2>Example</h2>
 * <h3>The traditional, XML-based approach</h3>
 * Most Spring users building a web application will need to register Spring's {@code
 * DispatcherServlet}. For reference, in WEB-INF/web.xml, this would typically be done as
 * follows:
 * <pre class="code">
 * {@code
 * <servlet>
 *   <servlet-name>dispatcher</servlet-name>
 *   <servlet-class>
 *     org.springframework.web.servlet.DispatcherServlet
 *   </servlet-class>
 *   <init-param>
 *     <param-name>contextConfigLocation</param-name>
 *     <param-value>/WEB-INF/spring/dispatcher-config.xml</param-value>
 *   </init-param>
 *   <load-on-startup>1</load-on-startup>
 * </servlet>
 *
 * <servlet-mapping>
 *   <servlet-name>dispatcher</servlet-name>
 *   <url-pattern>/</url-pattern>
 * </servlet-mapping>}</pre>
 *
 * <h3>The code-based approach with {@code WebApplicationInitializer}</h3>
 * Here is the equivalent {@code DispatcherServlet} registration logic,
 * {@code WebApplicationInitializer}-style:
 * <pre class="code">
 * public class MyWebAppInitializer implements WebApplicationInitializer {
 *
 *    &#064;Override
 *    public void onStartup(ServletContext container) {
 *      XmlWebApplicationContext appContext = new XmlWebApplicationContext();
 *      appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
 *
 *      ServletRegistration.Dynamic dispatcher =
 *        container.addServlet("dispatcher", new DispatcherServlet(appContext));
 *      dispatcher.setLoadOnStartup(1);
 *      dispatcher.addMapping("/");
 *    }
 *
 * }</pre>
 *
 * As an alternative to the above, you can also extend from {@link
 * org.springframework.web.servlet.support.AbstractDispatcherServletInitializer}.
 *
 * As you can see, thanks to Servlet 3.0's new {@link ServletContext#addServlet} method
 * we're actually registering an <em>instance</em> of the {@code DispatcherServlet}, and
 * this means that the {@code DispatcherServlet} can now be treated like any other object
 * -- receiving constructor injection of its application context in this case.
 *
 * <p>This style is both simpler and more concise. There is no concern for dealing with
 * init-params, etc, just normal JavaBean-style properties and constructor arguments. You
 * are free to create and work with your Spring application contexts as necessary before
 * injecting them into the {@code DispatcherServlet}.
 *
 * <p>Most major Spring Web components have been updated to support this style of
 * registration.  You'll find that {@code DispatcherServlet}, {@code FrameworkServlet},
 * {@code ContextLoaderListener} and {@code DelegatingFilterProxy} all now support
 * constructor arguments. Even if a component (e.g. non-Spring, other third party) has not
 * been specifically updated for use within {@code WebApplicationInitializers}, they still
 * may be used in any case. The Servlet 3.0 {@code ServletContext} API allows for setting
 * init-params, context-params, etc programmatically.
 *
 * <h2>A 100% code-based approach to configuration</h2>
 * In the example above, {@code WEB-INF/web.xml} was successfully replaced with code in
 * the form of a {@code WebApplicationInitializer}, but the actual
 * {@code dispatcher-config.xml} Spring configuration remained XML-based.
 * {@code WebApplicationInitializer} is a perfect fit for use with Spring's code-based
 * {@code @Configuration} classes. See @{@link
 * org.springframework.context.annotation.Configuration Configuration} Javadoc for
 * complete details, but the following example demonstrates refactoring to use Spring's
 * {@link org.springframework.web.context.support.AnnotationConfigWebApplicationContext
 * AnnotationConfigWebApplicationContext} in lieu of {@code XmlWebApplicationContext}, and
 * user-defined {@code @Configuration} classes {@code AppConfig} and
 * {@code DispatcherConfig} instead of Spring XML files. This example also goes a bit
 * beyond those above to demonstrate typical configuration of the 'root' application
 * context and registration of the {@code ContextLoaderListener}:
 * <pre class="code">
 * public class MyWebAppInitializer implements WebApplicationInitializer {
 *
 *    &#064;Override
 *    public void onStartup(ServletContext container) {
 *      // Create the 'root' Spring application context
 *      AnnotationConfigWebApplicationContext rootContext =
 *        new AnnotationConfigWebApplicationContext();
 *      rootContext.register(AppConfig.class);
 *
 *      // Manage the lifecycle of the root application context
 *      container.addListener(new ContextLoaderListener(rootContext));
 *
 *      // Create the dispatcher servlet's Spring application context
 *      AnnotationConfigWebApplicationContext dispatcherContext =
 *        new AnnotationConfigWebApplicationContext();
 *      dispatcherContext.register(DispatcherConfig.class);
 *
 *      // Register and map the dispatcher servlet
 *      ServletRegistration.Dynamic dispatcher =
 *        container.addServlet("dispatcher", new DispatcherServlet(dispatcherContext));
 *      dispatcher.setLoadOnStartup(1);
 *      dispatcher.addMapping("/");
 *    }
 *
 * }</pre>
 *
 * As an alternative to the above, you can also extend from {@link
 * org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer}.
 *
 * Remember that {@code WebApplicationInitializer} implementations are <em>detected
 * automatically</em> -- so you are free to package them within your application as you
 * see fit.
 *
 * <h2>Ordering {@code WebApplicationInitializer} execution</h2>
 * {@code WebApplicationInitializer} implementations may optionally be annotated at the
 * class level with Spring's @{@link org.springframework.core.annotation.Order Order}
 * annotation or may implement Spring's {@link org.springframework.core.Ordered Ordered}
 * interface. If so, the initializers will be ordered prior to invocation. This provides
 * a mechanism for users to ensure the order in which servlet container initialization
 * occurs. Use of this feature is expected to be rare, as typical applications will likely
 * centralize all container initialization within a single {@code WebApplicationInitializer}.
 *
 * <h2>Caveats</h2>
 *
 * <h3>web.xml versioning</h3>
 * <p>{@code WEB-INF/web.xml} and {@code WebApplicationInitializer} use are not mutually
 * exclusive; for example, web.xml can register one servlet, and a {@code
 * WebApplicationInitializer} can register another. An initializer can even
 * <em>modify</em> registrations performed in {@code web.xml} through methods such as
 * {@link ServletContext#getServletRegistration(String)}. <strong>However, if
 * {@code WEB-INF/web.xml} is present in the application, its {@code version} attribute
 * must be set to "3.0" or greater, otherwise {@code ServletContainerInitializer}
 * bootstrapping will be ignored by the servlet container.</strong>
 *
 * <h3>Mapping to '/' under Tomcat</h3>
 * <p>Apache Tomcat maps its internal {@code DefaultServlet} to "/", and on Tomcat versions
 * &lt;= 7.0.14, this servlet mapping <em>cannot be overridden programmatically</em>.
 * 7.0.15 fixes this issue. Overriding the "/" servlet mapping has also been tested
 * successfully under GlassFish 3.1.<p>
 *
 * @author Chris Beams
 * @since 3.1
 * @see SpringServletContainerInitializer
 * @see org.springframework.web.context.AbstractContextLoaderInitializer
 * @see org.springframework.web.servlet.support.AbstractDispatcherServletInitializer
 * @see org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer
 */
public interface WebApplicationInitializer {

    /**
     * Configure the given {@link ServletContext} with any servlets, filters, listeners
     * context-params and attributes necessary for initializing this web application. See
     * examples {@linkplain WebApplicationInitializer above}.
     * @param servletContext the {@code ServletContext} to initialize
     * @throws ServletException if any call against the given {@code ServletContext}
     * throws a {@code ServletException}
     */
    void onStartup(ServletContext servletContext) throws ServletException;

}

所以在容器启动时就会自动找到我们的初始化类ServletWebApplicationInitializer

@Configuration 注解特别说明

我们要是有多个配置文件，他们之间如何相互引用呢？答案就是使用@Import注解，比如我们有DataSourceConfig配置，想要在RootConfig配置中引用，代码如下。

package cn.ycx.config;

import javax.sql.DataSource;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.FilterType;
import org.springframework.context.annotation.Import;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.support.StandardServletMultipartResolver;

@Configuration
@ComponentScan(basePackages = {"cn.ycx"}, excludeFilters = {
        @Filter( type=FilterType.ANNOTATION, value=org.springframework.stereotype.Controller.class)
        })
@Import(DataSourceConfig.class) //引用其他配置中的Bean
public class RootConfig {
    @Bean
    public MultipartResolver multipartResolver() {
        System.out.println("multipartResolver...");
        return new StandardServletMultipartResolver();
    }
    @Bean
    public JdbcTemplate jdbcTemplate(DataSource dataSource) {
        System.out.println("jdbcTemplate...");
        return new JdbcTemplate(dataSource);
    }
}

package cn.ycx.config;

import javax.naming.NamingException;
import javax.sql.DataSource;

import org.springframework.context.annotation.Bean;
import org.springframework.jndi.JndiObjectFactoryBean;

public class DataSourceConfig {
    @Bean
    public DataSource dataSource() throws IllegalArgumentException, NamingException {
        System.out.println("dataSource...");
        JndiObjectFactoryBean jndi = new JndiObjectFactoryBean();
        jndi.setJndiName("jdbc/mysql");
        jndi.setResourceRef(true);//自动添加 java:comp/env/ 前缀
        jndi.setProxyInterface(javax.sql.DataSource.class);
        jndi.afterPropertiesSet();
        return (DataSource) jndi.getObject();
    }    
}

注意DataSourceConfig没有加@Configuration注解

2、Xml配置方式

这种方式很简单，主要是配置web.xml和servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>web</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <context-param>
    <param-name>spring.profiles.default</param-name>
    <param-value>dev</param-value>
  </context-param>
  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>WEB-INFcontext.xml</param-value>
  </context-param>
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>
  <servlet>
    <servlet-name>ds</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>WEB-INFservlet.xml</param-value>
    </init-param>
    <init-param>
      <param-name>spring.profiles.default</param-name>
      <param-value>dev</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>ds</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

<?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:mvc="http://www.springframework.org/schema/mvc"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:c="http://www.springframework.org/schema/c"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd">
    
      <mvc:annotation-driven></mvc:annotation-driven>
      <context:component-scan base-package="cn.ycx"></context:component-scan>
    <mvc:default-servlet-handler />
    <!-- 会加载所有的properties文件 -->
    <context:property-placeholder/>
    <bean id="viewResolver" 
      class="org.springframework.web.servlet.view.InternalResourceViewResolver" 
      p:prefix="/WEB-INF/views" p:suffix=".jsp"></bean>
</beans>

剩下的就是编写控制器

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原文地址：https://www.cnblogs.com/yangchongxing/p/8871370.html