用来记录一些原创性的总结
如果在使用SpringMVC时不希望采用XML的配置方式，而采用基于Java类的配置也是可以的。如果还希望在web.xml中配置DispatcherServlet，则需要通过init-param指定contextClass为AnnotationConfigWebApplicationContext，然后把contextConfigLocation指定为SpringMVC配置Java类的全路径名称。
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextClass</param-name>
<param-value>org.springframework.web.context.support.AnnotationConfigWebApplicationContext</param-value>
</init-param>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>com.elim.spring.mvc.MvcConfiguration</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
在Java配置类中就可以按照正常的Java类配置那样定义，如下则定义了扫描com.elim.spring.mvc.controller包下面的Class。
@ComponentScan(basePackages = "com.elim.spring.mvc.controller")
public class MvcConfiguration {
}
如果定义DispatcherServlet时还是指定的配置文件为XML文件，则也可以在对应的XML配置文件中定义上面的Java配置类为一个bean，效果是一样的。
之后可以在该配置类中定义一些SpringMVC配置bean，比如下面就定义了一个InternalResourceViewResolver。
@ComponentScan(basePackages = "com.elim.spring.mvc.controller")
public class MvcConfiguration {
@Bean
public InternalResourceViewResolver newInternalResourceViewResolver() {
InternalResourceViewResolver resolver = new InternalResourceViewResolver();
resolver.setPrefix("/WEB-INF/view/");
resolver.setSuffix(".jsp");
return resolver;
}
}
在进行配置时也可以选择实现WebMvcConfigurer接口进行配置，或者选择继承自抽象类WebMvcConfigurerAdapter，然后重写感兴趣的方法。以下是WebMvcConfigurer的定义。
public interface WebMvcConfigurer {
/**
* Add {@link Converter}s and {@link Formatter}s in addition to the ones
* registered by default.
*/
void addFormatters(FormatterRegistry registry);
/**
* Configure the {@link HttpMessageConverter}s to use in argument resolvers
* and return value handlers that support reading and/or writing to the
* body of the request and response. If no message converters are added to
* the list, default converters are added instead.
* @param converters initially an empty list of converters
*/
void configureMessageConverters(List<HttpMessageConverter<?>> converters);
/**
* Provide a custom {@link Validator} instead of the one created by default.
* The default implementation, assuming JSR-303 is on the classpath, is:
* {@link org.springframework.validation.beanvalidation.OptionalValidatorFactoryBean}.
* Leave the return value as {@code null} to keep the default.
*/
Validator getValidator();
/**
* Configure content negotiation options.
*/
void configureContentNegotiation(ContentNegotiationConfigurer configurer);
/**
* Configure asynchronous request handling options.
*/
void configureAsyncSupport(AsyncSupportConfigurer configurer);
/**
* Helps with configuring HandlerMappings path matching options such as trailing slash match,
* suffix registration, path matcher and path helper.
* Configured path matcher and path helper instances are shared for:
* <ul>
* <li>RequestMappings</li>
* <li>ViewControllerMappings</li>
* <li>ResourcesMappings</li>
* </ul>
* @since 4.0.3
*/
void configurePathMatch(PathMatchConfigurer configurer);
/**
* Add resolvers to support custom controller method argument types.
* <p>This does not override the built-in support for resolving handler
* method arguments. To customize the built-in support for argument
* resolution, configure {@link RequestMappingHandlerAdapter} directly.
* @param argumentResolvers initially an empty list
*/
void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers);
/**
* Add handlers to support custom controller method return value types.
* <p>Using this option does not override the built-in support for handling
* return values. To customize the built-in support for handling return
* values, configure RequestMappingHandlerAdapter directly.
* @param returnValueHandlers initially an empty list
*/
void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers);
/**
* Configure the {@link HandlerExceptionResolver}s to handle unresolved
* controller exceptions. If no resolvers are added to the list, default
* exception resolvers are added instead.
* @param exceptionResolvers initially an empty list
*/
void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers);
/**
* Add Spring MVC lifecycle interceptors for pre- and post-processing of
* controller method invocations. Interceptors can be registered to apply
* to all requests or be limited to a subset of URL patterns.
*/
void addInterceptors(InterceptorRegistry registry);
/**
* Provide a custom {@link MessageCodesResolver} for building message codes
* from data binding and validation error codes. Leave the return value as
* {@code null} to keep the default.
*/
MessageCodesResolver getMessageCodesResolver();
/**
* Configure simple automated controllers pre-configured with the response
* status code and/or a view to render the response body. This is useful in
* cases where there is no need for custom controller logic -- e.g. render a
* home page, perform simple site URL redirects, return a 404 status with
* HTML content, a 204 with no content, and more.
*/
void addViewControllers(ViewControllerRegistry registry);
/**
* Configure view resolvers to translate String-based view names returned from
* controllers into concrete {@link org.springframework.web.servlet.View}
* implementations to perform rendering with.
*/
void configureViewResolvers(ViewResolverRegistry registry);
/**
* Add handlers to serve static resources such as images, js, and, css
* files from specific locations under web application root, the classpath,
* and others.
*/
void addResourceHandlers(ResourceHandlerRegistry registry);
/**
* Configure a handler to delegate unhandled requests by forwarding to the
* Servlet container's "default" servlet. A common use case for this is when
* the {@link DispatcherServlet} is mapped to "/" thus overriding the
* Servlet container's default handling of static resources.
*/
void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer);
}
采用继承WebMvcConfigurerAdapter的方式，上面的配置可以改写为如下这样。
@ComponentScan(basePackages = "com.elim.spring.mvc.controller")
public class MvcConfiguration extends WebMvcConfigurerAdapter {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.jsp("/WEB-INF/view/", ".jsp");
}
}
在使用Java配置时也可以在配置类上使用@EnableWebMvc，这样SpringMVC将进行一些自动配置。具体的自动配置内容可以参考WebMvcConfigurationSupport类的定义。当然也可以选择直接继承自WebMvcConfigurationSupport，然后进行部分方法重写。
@EnableWebMvc
@ComponentScan(basePackages = "com.elim.learn.spring.mvc.controller")
public class MvcConfiguration extends WebMvcConfigurerAdapter {
@Override
public void configureViewResolvers(ViewResolverRegistry registry) {
registry.jsp("/WEB-INF/view/", ".jsp");
}
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(new MappingJackson2HttpMessageConverter());
converters.add(new StringHttpMessageConverter(Charset.defaultCharset()));
}
}
如果希望不在web.xml文件中定义DispatcherServlet，而是完全通过程序来定义，可以选择定义一个AbstractDispatcherServletInitializer的子类，然后实现其中的抽象方法。如果是需要使用基于注解的配置，则可以直接继承AbstractAnnotationConfigDispatcherServletInitializer类。AbstractAnnotationConfigDispatcherServletInitializer中定义了三个抽象方法，getRootConfigClasses()用来定义根配置的类，即对应根ApplicationContext的配置类，如果这个配置还是通过在web.xml中配置的则可以忽略它；getServletConfigClasses()则对应SpringMVC配置的配置类；getServletMappings()则用于指定需要映射的地址。以下就是自定义的一个初始化类，它会在容器启动的时候自动发现，然后进行SpringMVC的初始化工作。
public class SpringInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
@Override
protected Class<?>[] getRootConfigClasses() {
return null;
}
@Override
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[]{MvcConfiguration.class};
}
@Override
protected String[] getServletMappings() {
return new String[]{"/"};
}
}
（注：本文是基于Spring4.1.0所写）