通过annotation获取request中的attribute

在spring web工程中的controller可以通过@RequestParam获取request中的参数，也可以通过@PathVariable获取请求url中的参数。但是如果想要从request中获取attribute却是没有现在的注解（也许是没有找到吧），那只有自己对手，丰衣足食了。

注解定义

​

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;

​

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestAttribute {

    String value() default "";
    boolean required() default true;
}

注解处理定义

​

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;

import org.springframework.core.MethodParameter;
import org.springframework.web.bind.ServletRequestBindingException;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver;

import path to RequestAttribute;

​

public class RequestAttributeMethodArgumentResolver extends AbstractNamedValueMethodArgumentResolver {

​

public RequestAttributeMethodArgumentResolver() {
    super(null);
}

@Override
protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
    RequestAttribute annotation = parameter.getParameterAnnotation(RequestAttribute.class);
    return new RequestAttributeNamedValueInfo(annotation);
}

@Override
protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
    HttpServletRequest httpServletRequest = request.getNativeRequest(HttpServletRequest.class);
    Object attribute = httpServletRequest.getAttribute(name);
    return attribute;
}

​

    @Override
    protected void handleMissingValue(String name, MethodParameter parameter) throws ServletException {
        String paramType = parameter.getParameterType().getSimpleName();
        String methodName = parameter.getMethod().getName();
        throw new ServletRequestBindingException(String.format("call %s, Missing request attribute: %s for method parameter type[%s]", methodName, name, paramType));
    }

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(RequestAttribute.class);
    }

    private class RequestAttributeNamedValueInfo extends NamedValueInfo {
        private RequestAttributeNamedValueInfo() {
            super("", false, null);
        }

        public RequestAttributeNamedValueInfo(RequestAttribute annotation) {
            super(annotation.value(), annotation.required(), null);
        }
    }

}

接下来就要在spring的配置文件中添加配置了

​

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="customArgumentResolvers">
        <list>
            <bean class="path to RequestAttributeMethodArgumentResolver" />
        </list>
    </property>
</bean>
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"></bean>

不同的工程配置方式可能有点不一样，但是大同小异都差不多