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。



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。


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() {  
new StringBuilder();  
        sb.append(name);  
"-");  
        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,  
throws Exception {  
new ArrayList<User>();  
"name");  
"age");  
          
          
for (int i = 0; i < names.length; i++) {  
new User();  
            BeanWrapper beanWrapper = PropertyAccessorFactory.forBeanPropertyAccess(user);  
              
            String name = names[i];  
            String age = ages[i];  
"name", name);  
"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) {  
new StringBuilder();  
for (User u : list) {  
            b.append(u);  
"<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>