springMvc 常用接口HandlerMethodArgumentResolver使用

之前写的http传输json进行服务端接口与客户端对接，以及restful实现这篇文章里提到关于json传输接收，我是在controller里来做json解析处理，如果每个地方都要用到json解析，那每个地方都这么写就显得代码很乱，当然也可以抽取到一个工具类里，但又觉得不优雅，假如我们有这么个注解@Json2Bean在controller参数对象中就能自动帮我们把json解析为我们要对象那将多美好呀。那么这里将应用springmvc  HandlerMethodArgumentResolver这个接口以及自定义注解来实现一个关于json的解析；

实现步骤如下：

1）自定义注解：

package com.cwh.springmvc.Annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({java.lang.annotation.ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Json2Bean {

}

2）利用 HandlerMethodArgumentResolver接口实现数据绑定：

package com.cwh.springmvc.resolver;

import java.io.BufferedInputStream;
import java.io.BufferedReader;

import javax.servlet.http.HttpServletRequest;

import net.sf.json.JSONObject;

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.cwh.springmvc.Annotation.Json2Bean;

public class Json2BeanArgumentResolver implements HandlerMethodArgumentResolver{

	@Override
	public boolean supportsParameter(MethodParameter paramMethodParameter) {
		// 仅对有fastjson注解有效
		return paramMethodParameter.hasParameterAnnotation(Json2Bean.class);
	}

	@Override
	public Object resolveArgument(MethodParameter paramMethodParameter,
			ModelAndViewContainer paramModelAndViewContainer,
			NativeWebRequest paramNativeWebRequest,
			WebDataBinderFactory paramWebDataBinderFactory) throws Exception {
		HttpServletRequest request = paramNativeWebRequest.getNativeRequest(HttpServletRequest.class);
        // content-type不是json的不处理
        if (!request.getContentType().contains("application/json")) {
            return null;
        }
        StringBuffer str = new StringBuffer(); 
		try {
			   BufferedInputStream in = new BufferedInputStream(request.getInputStream());
			      int i;
			      char c;
			      while ((i=in.read())!=-1) {
			      c=(char)i;
			      str.append(c);
			      }
			     }catch (Exception ex) {
			   ex.printStackTrace();
			   }
        JSONObject obj= JSONObject.fromObject(str.toString());
        return JSONObject.toBean(obj,paramMethodParameter.getParameterType());
    }

}

3）springmvc配置文件配置：

<mvc:annotation-driven>
   		<mvc:argument-resolvers>
	        <bean class="com.cwh.springmvc.resolver.Json2BeanArgumentResolver"/>
	    </mvc:argument-resolvers>
   </mvc:annotation-driven>

注：这个<mvc:annotation-driven>标签是3.1版本的

4）controller实现应用上@json2Bean这个注解：

@RequestMapping("/getUserByName")
	public @ResponseBody User getUserByName(@Json2Bean User userform){
		System.out.println(userform);
		String name = userform.getUsername();
		User user= userservice.getUserByName(name);
		
		return user;
	}

5）模拟发送一笔json请求测试：

@Test
	public void HttpPostData() {  
	      try { 
	          HttpClient httpclient = new DefaultHttpClient();  
	          String uri = "http://localhost:8080/springMVC/user/getUserByName"; 
	          HttpPost httppost = new HttpPost(uri);   
	          //添加http头信息 
	          httppost.addHeader("Content-Type", "application/json"); 
	          JSONObject obj = new JSONObject();
	          obj.put("username", "cwh"); 
	          obj.put("password", "password"); 
	          httppost.setEntity(new StringEntity(obj.toString()));     
	          HttpResponse response;  
	          response = httpclient.execute(httppost);  
	          //检验状态码，如果成功接收数据  
	          int code = response.getStatusLine().getStatusCode();  
	          System.out.println(code+"code");
	          if (code == 200) {  
	              String rev = EntityUtils.toString(response.getEntity());//返回json格式： {"id": "","name": ""}         
	              obj= JSONObject.fromObject(rev);
	              System.out.println(obj.get("username"));
	              User user = (User)JSONObject.toBean(obj,User.class);
	              System.out.println("返回数据==="+user.toString());
	          } 
	          } catch (ClientProtocolException e) { 
	        	  e.printStackTrace();
	          } catch (IOException e) {  
	        	  e.printStackTrace();
	          } catch (Exception e) { 
	        	  e.printStackTrace();
	          } 
	     }

6）测试结果：

ok！这样服务端看起来代码就简洁多了