使用HandlerMethodArgumentResolver接口自定义Spring MVC的参数接受规则

1.自定义Spring MVC接受List参数

SpringMVC3.1引入了HandlerMethodArgumentResolver接口，spring调用该接口实现Controller的参数装配。HandlerMethodArgumentResolver实现类中会调用DataBinder，Converter等。

常用的该接口实现类有:

ServletModelAttributeMethodProcessor:实体类的组装用它实现。

RequestParamMethodArgumentResolver：基本数据类型如String用它实现。

在我学习过程中，发现对List类型的参数SpringMVC没有提供默认实现。我参照Spring的示例 通过实现 HandlerMethodArgumentResolver接口，实现对List参数的组装。

示例中用到的Model类：

 package com.weishubin.springmvc.model;

 public class User {
     private String name;
     private int age;
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }

     public String toString() {
         StringBuilder sb = new StringBuilder();
         sb.append(name);
         sb.append("-");
         sb.append(age);
         return sb.toString();
     }
 }

注解类：

 package com.weishubin.springmvc.listargument;

 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 ListAttribute {

 }

实现了HandlerMethodArgumentResolver接口的参数解析器：

 package com.weishubin.springmvc.listargument;

 import java.util.ArrayList;
 import java.util.List;

 import org.springframework.beans.BeanWrapper;
 import org.springframework.beans.PropertyAccessorFactory;
 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.weishubin.springmvc.model.User;

 public class ListArgumentResolver implements HandlerMethodArgumentResolver {

     public boolean supportsParameter(MethodParameter parameter) {
         //仅作用于添加了注解ListAttribute的参数
         return parameter.getParameterAnnotation(ListAttribute.class) != null;
     }

     public Object resolveArgument(MethodParameter parameter,
             ModelAndViewContainer mavContainer, NativeWebRequest webRequest,
             WebDataBinderFactory binderFactory) throws Exception {
         List<User> users = new ArrayList<User>();
         String[] names = webRequest.getParameterValues("name");
         String[] ages = webRequest.getParameterValues("age");


         for (int i = 0; i < names.length; i++) {
             User user = new User();
             BeanWrapper beanWrapper = PropertyAccessorFactory.forBeanPropertyAccess(user);

             String name = names[i];
             String age = ages[i];
             beanWrapper.setPropertyValue("name", name);
             beanWrapper.setPropertyValue("age", age);

             users.add(user);
         }
         return users;
     }

 }

Controller类：

 package com.weishubin.springmvc.listargument;

 import java.util.List;

 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;

 import com.weishubin.springmvc.model.User;

 @Controller
 public class ListArgumentController {

     @ResponseBody
     @RequestMapping("/list")
     public String argumentResolver(@ListAttribute List<User> list) {
         StringBuilder b = new StringBuilder();
         for (User u : list) {
             b.append(u);
             b.append("<br/>");
         }
         return b.toString();
     }
 }

配置文件：

 <mvc:annotation-driven>
         <mvc:argument-resolvers>
             <bean class="com.weishubin.springmvc.listargument.ListArgumentResolver"/>
         </mvc:argument-resolvers>
     </mvc:annotation-driven>

2.对接受的参数进行Base64解密处理

1.自定义注解

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;

/**
 * Description: <br/>
 * Tsp请求，入参自动Base64转码注解
 * @date 2016年4月8日 下午4:26:14
 *
 */
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TspRequestBase64 {
}

2.定义对使用注解的入参处理

import java.io.InputStreamReader;
import java.nio.charset.Charset;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.lang3.StringUtils;
import org.springframework.core.MethodParameter;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.util.FileCopyUtils;
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.alibaba.fastjson.JSONObject;
import com.xx.movie.confirmation.common.annotation.TspRequestBase64;

/**
 * Description: <br/>
 * Tsp服务，入参进行Base64自动转码
 * @date 2016年4月8日 下午3:46:41
 *
 */
public class TspRequestBase64Resolver implements HandlerMethodArgumentResolver {

    private Charset defaultCharset = Charset.forName("UTF-8");

    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(TspRequestBase64.class);
    }

    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest,
            WebDataBinderFactory binderFactory) throws Exception {
        HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
        HttpInputMessage message = new ServletServerHttpRequest(request);
        Charset charset = this.getContentCharset(message.getHeaders().getContentType());
        String body = FileCopyUtils.copyToString(new InputStreamReader(request.getInputStream(), charset));

        //如果是GET请求，body应该是空，重新获取
        if (StringUtils.isEmpty(body)) {
            body = request.getQueryString();
        }

        byte[] content = null;

        if(body != null && body.length() > 0){
            if (Base64.isBase64(body)) {
                content = Base64.decodeBase64(body);
                
            } else {
                content = body.getBytes(charset);
            }
        }
        
        return (content == null) ? null : JSONObject.parseObject(content, parameter.getParameterType());
    }

    //获取charset
    public Charset getContentCharset(MediaType mediaType) {

        if (mediaType != null && mediaType.getCharSet() != null) {
            return mediaType.getCharSet();
        } else {
            return this.defaultCharset;
        }

    }

}

3.配置spring-mvc.xml文件

<!-- 启用spring mvc 注解 -->
	<mvc:annotation-driven>
		<mvc:argument-resolvers>
			<!-- aop解析TspRequest注解 -->
			<beans:bean
				class="com.xx.movie.confirmation.common.util.TspRequestBase64Resolver"></beans:bean>
			<beans:bean
				class="com.xx.nfbird.web.argument.JsonMapperArgumentResolver"></beans:bean>
			<!-- pagination -->
			<beans:bean
				class="com.xx.nfbird.web.argument.PaginationArgumentResolver"></beans:bean>
		</mvc:argument-resolvers>
	</mvc:annotation-driven>

4.Spring MVC中使用

@RequestMapping(value = "/order/take", method = RequestMethod.POST)
	@ResponseJson(translate = true)
	public SeqId orderOccupy(@TspRequestBase64 OrderOccupyRequestVo occupyVo) throws Exception {
	

解析：

        传入的参数必须是Base64位加密之后的，在Spring MVC接受到参数后，回先进行参数的解码

3.使用Shiro+HanderMethodArgumentResolver在入参时，获取安全上下文

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>