SpringMVC杂记(十七) HandlerMethodArgumentResolver接口应用example
自从spring3.1 开始就有了这个接口，可以为@RequestMapping标注的方法扩展传入的参数。
以shiro为例，扩展一个标注，@CurrentUser,只要有这个标注，就可以在shiro的安全上下文中取出适当的对象直接从参数传入，request响应函数。
import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Documented@Target({ElementType.PARAMETER})@Retention(RetentionPolicy.RUNTIME)public @interface CurrentUser {}@RequestMapping(value = "/test1")public @ResponseBody String test1(@CurrentUser Long userId) {return userId.toString();}@RequestMapping(value = "/test2")public @ResponseBody String test2(@CurrentUser UserDetails userDetails) {return userDetails.toString();}import java.lang.annotation.Annotation;import org.springframework.core.MethodParameter;import org.springframework.web.bind.support.WebDataBinderFactory;import org.springframework.web.context.request.NativeWebRequest;import org.springframework.web.method.support.HandlerMethodArgumentResolver;import org.springframework.web.method.support.ModelAndViewContainer;import com.github.yingzhuo.mycar2.annotation.CurrentUser;import com.github.yingzhuo.mycar2.security.SecurityUtils;import com.github.yingzhuo.mycar2.security.UserDetails;public class CurrentUserHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {@Overridepublic boolean supportsParameter(MethodParameter parameter) {Class<?> klass = parameter.getParameterType();if (klass.isAssignableFrom(UserDetails.class) || klass.isAssignableFrom(Long.class)) {Annotation[] as = parameter.getParameterAnnotations();for (Annotation a : as) {if (a.annotationType() == CurrentUser.class) {return true;}}}return false;}@Overridepublic Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest,WebDataBinderFactory binderFactory) throws Exception {if ((SecurityUtils.isAuthenticated() || SecurityUtils.isRemembered()) == false) {return null;}Class<?> klass = parameter.getParameterType();UserDetails userDetails = SecurityUtils.getUserDetails();if (klass.isAssignableFrom(UserDetails.class)) {return SecurityUtils.getUserDetails();}if (klass.isAssignableFrom(Long.class)) {return userDetails != null ? userDetails.getId() : null;}return null;}}<mvc:annotation-driven><mvc:argument-resolvers><bean /></mvc:argument-resolvers></mvc:annotation-driven>