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 {

	@Override
	public 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;
	}

	@Override
	public 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;
	}
}

最后，需要配置一下

<mvc:annotation-driven>
	<mvc:argument-resolvers>
		<bean class="xxx.yyy.CurrentUserHandlerMethodArgumentResolver" />
	</mvc:argument-resolvers>
</mvc:annotation-driven>