前言
上一篇文章介绍了Spring的事务管理，接下来开始介绍Spring的Mvc模块。首先介绍一下SpringMvc的基础模块，自定义Controller，RequestMapping注解，来实现自定义加载。
自定义Controller
Spring开启Mvc的主要是通过EnableWebMvc注解，观察源码就会发现，这个注解注入了DelegatingWebMvcConfiguration这个类，它继承了WebMvcConfigurationSupport，注入了必要的Bean。
Spring嵌入web应用容器的入口类是DispatcherServlet，这个类会读取WebApplicationContext中的必要的bean的信息，来提供mvc的服务。这篇文章先介绍下Controller RequestMapping的注入和使用。
完整的代码在Github上，这里介绍几个主要的类。
- 先定义自己的注解，MyController加上了Component注解，这样可以被Spring识别加载。MyRequestMapping则完全复用RequestMapping的属性，因为是附加是属性，所以就不需要加上Component注解了。
@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface MyController {
String value() default "";
}
@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyRequestMapping {
String name() default "";
String[] value() default {};
RequestMethod[] method() default {};
String[] params() default {};
String[] headers() default {};
String[] consumes() default {};
String[] produces() default {};
}
- 定义controller和RequestMapping。
@MyController
public static class IndexController {
@MyRequestMapping("/")
@ResponseBody
public Map index() {
Map<String, String> map = new HashMap<String, String>();
map.put("result", "hello world");
return map;
}
}
- 加载自定义的注解，这里继承自RequestMappingHandlerMapping重载了isHandler和getMappingForMethod方法来加载自定义的注解，并根据MyRequestMapping的属性来生成RequestMappingInfo。
public static class MyRequestMappingHandlerMapping extends RequestMappingHandlerMapping {
@Override
protected boolean isHandler(Class<?> beanType) {
return ((AnnotationUtils.findAnnotation(beanType, MyController.class) != null) || (
AnnotationUtils.findAnnotation(beanType, MyRequestMapping.class) != null));
}
private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
MyRequestMapping requestMapping = AnnotatedElementUtils
.findMergedAnnotation(element, MyRequestMapping.class);
RequestCondition<?> condition = (element instanceof Class<?> ?
getCustomTypeCondition((Class<?>) element) :
getCustomMethodCondition((Method) element));
if (requestMapping == null) {
return null;
}
return RequestMappingInfo.paths(resolveEmbeddedValuesInPatterns(requestMapping.value()))
.methods(requestMapping.method()).params(requestMapping.params()).headers(requestMapping.headers())
.consumes(requestMapping.consumes()).produces(requestMapping.produces())
.mappingName(requestMapping.name()).customCondition(condition).build();
}
@Override
protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
RequestMappingInfo info = createRequestMappingInfo(method);
if (info != null) {
RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
if (typeInfo != null) {
info = typeInfo.combine(info);
}
}
return info;
}
}
这个类继承了HandlerMapping接口，观察DispatcherServlet的源码就会发现，HandlerMapping接受httpRequest并查找到对应的method。
这个类保存了RequestMapping的注解的方法，保存在MappingRegistry的mappingLookup和urlLookup中（这里是Spring4的实现方式，Spring3会不一样），
其中urlLookup是用于直接查找的directPathMatches，如果没有directPathMatches，在遍历mappingLookup，查找匹配的处理方法。
private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<T, HandlerMethod>();
private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<String, T>();
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<Match>();
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
.....
}
- 注入RequestMappingHandlerMapping，这里继承了WebMvcConfigurationSupport，然后重载了requestMappingHandlerMapping的注入方法。
RequestMappingHandlerMapping的配置方法跟WebMvcConfigurationSupport一致。
@Configuration
public static class MyWebMvcConfigurationSupport extends WebMvcConfigurationSupport {
@Bean
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
MyRequestMappingHandlerMapping handlerMapping = new MyRequestMappingHandlerMapping();
handlerMapping.setOrder(0);
handlerMapping.setInterceptors(getInterceptors());
handlerMapping.setContentNegotiationManager(mvcContentNegotiationManager());
handlerMapping.setCorsConfigurations(getCorsConfigurations());
PathMatchConfigurer configurer = getPathMatchConfigurer();
if (configurer.isUseSuffixPatternMatch() != null) {
handlerMapping.setUseSuffixPatternMatch(configurer.isUseSuffixPatternMatch());
}
if (configurer.isUseRegisteredSuffixPatternMatch() != null) {
handlerMapping.setUseRegisteredSuffixPatternMatch(configurer.isUseRegisteredSuffixPatternMatch());
}
if (configurer.isUseTrailingSlashMatch() != null) {
handlerMapping.setUseTrailingSlashMatch(configurer.isUseTrailingSlashMatch());
}
if (configurer.getPathMatcher() != null) {
handlerMapping.setPathMatcher(configurer.getPathMatcher());
}
if (configurer.getUrlPathHelper() != null) {
handlerMapping.setUrlPathHelper(configurer.getUrlPathHelper());
}
return handlerMapping;
}
}
-
DispatcherServlet是web请求的处理类，接收WebApplicationContext和ServletConfig进行必要参数的初始化，
service方法，是处理请求的入口，接受request和response参数。简便起见，这里不启动web容器，而是用MockRequest和MockResponse来模拟处理请求。
@Configuration
public class CustomizeControllerTest {
public static void main(String[] args) throws ServletException, IOException {
// init WebApplicationContext
AnnotationConfigWebApplicationContext annotationConfigWebApplicationContext = new AnnotationConfigWebApplicationContext();
MockServletContext mockServletContext = new MockServletContext();
MockServletConfig mockServletConfig = new MockServletConfig(mockServletContext);
annotationConfigWebApplicationContext.setServletConfig(mockServletConfig);
annotationConfigWebApplicationContext.register(CustomizeControllerTest.class);
// init and start DispatcherServlet
DispatcherServlet dispatcherServlet = new DispatcherServlet(annotationConfigWebApplicationContext);
dispatcherServlet.init(mockServletConfig);
MockHttpServletResponse response = new MockHttpServletResponse();
MockHttpServletRequest request = new MockHttpServletRequest("GET", "/");
request.addHeader("Accept","application/json");
dispatcherServlet.service(request, response);
System.out.println(new String(response.getContentAsByteArray()));
}
}
结语
SpringMvc集成了Spring web flow的各个功能，这里先介绍下Spring的Controller和RequestMapping的使用，接下来会介绍包括HandlerAdapter和MassageConverter等更多功能。
