springMvc杂记(3)--如何接受多个对象参数

涉及代码路径--https://github.com/wangjiuong/springstudy/tree/master/SpringMvcMultiArgResolver

在代码开发过程中，参数的定义非常重要，目前springmvc提供的较多的参数获取方式，譬如  @PathVariable 和 @RequestParam，

或者通过增加如下注解

<mvc:annotation-driven>
    </mvc:annotation-driven>

mvc:annotation-driven默认增加了MappingJackson2HttpMessageConverter，可以将传递进来的body体解析成对应的JAVA对象。

但是存入如下问题
1、@PathVariable 和 @RequestParam只能解析基础的Java格式，int string boolean等，
2、MappingJackson2HttpMessageConverter只能将对象转变为一个JAVA Bean，
如果我们有两个java bean 定义如下：

public class Student {
	private String name;
	private int year;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getYear() {
		return year;
	}
	public void setYear(int year) {
		this.year = year;
	}
}

　　

public class Info {
    private String city;
    private String address;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

　　

如果我们定义了一个接口，需要传递这两个对象信息,采用MappingJackson2HttpMessageConverter就会比较麻烦。

这里讲解一个如何实现同时传递多个对象的方法，我们最终定义的接口如下

public Student addstudentpost(@JsonObject Student student,@JsonObject Info info)

原理是实现我们自定义的HandlerMethodArgumentResolver，并且插入到springMvc的参数解析队列中。

1、首先定义一个注解类

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

　2、其次实现自定义的参数解析类JsonObjectArgResolverHandler

public class JsonObjectArgResolverHandler implements HandlerMethodArgumentResolver {

    @Override public boolean supportsParameter(MethodParameter methodParameter) {
        return methodParameter.hasParameterAnnotation(JsonObject.class);
    }

    @Override public Object resolveArgument(MethodParameter methodParameter,
        ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest,
        WebDataBinderFactory webDataBinderFactory) throws Exception {
        try {
            JSONObject para = getRequestInfo(nativeWebRequest);
            Class<?> type = methodParameter.getParameterType();
            String name = methodParameter.getParameterName();
            if (null != para && para.containsKey(name)) {
                return JSON.parseObject(para.getString(name), type);
            }
        } catch (Exception e) {
        }
        return null;
    }



    private JSONObject getRequestInfo(NativeWebRequest webRequest) throws IOException {
        JSONObject para = new JSONObject();
        HttpServletRequest httpServletRequest =
            (HttpServletRequest) webRequest.getNativeRequest(HttpServletRequest.class);
        String method = httpServletRequest.getMethod();
        if (!method.equals("GET") && !method.equals("DELETE")) {

            if (null != httpServletRequest.getAttribute("para")) {
                try {
                    para = JSON.parseObject(httpServletRequest.getAttribute("para").toString());
                } catch (Exception e) {
                }
            } else {
                StringBuilder buffer = new StringBuilder();
                BufferedReader reader = httpServletRequest.getReader();
                String line;
                while ((line = reader.readLine()) != null) {
                    buffer.append(line);
                }
                httpServletRequest.setAttribute("para", buffer.toString());

                try {
                    para = JSON.parseObject(buffer.toString());
                } catch (Exception e) {
                }
            }
        } else {
            Map<String, String[]> parameterMap = webRequest.getParameterMap();
            for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
                String key = entry.getKey();
                String values = StringUtils.join(entry.getValue());
                para.put(key, values);
            }
        }
        return para;
    }

}

　　注意：

a、supportsParameter表明我们的类只支持解析带有JsonObject的对象解析。

b、httpServletRequest的body体只能读取一次，再次读取后就返回空，因为带有JsonObject注解的对象都会执行一遍，在第一次获取后需要将body体保存下来，以便下次使用。所有有如下的代码

     将body体保存

httpServletRequest.setAttribute("para", buffer.toString());

　读取Attribute，没有则从body体读取。

if (null != httpServletRequest.getAttribute("para")) {
                try {
                    para = JSON.parseObject(httpServletRequest.getAttribute("para").toString());
                } catch (Exception e) {
                }
            } else {

3、将 JsonObjectArgResolverHandler配置进xml文件中。

<mvc:annotation-driven>
        <mvc:argument-resolvers>
            <bean class="com.nuaa.handler.JsonObjectArgResolverHandler"></bean>
        </mvc:argument-resolvers>
        <mvc:return-value-handlers>
            <bean class="com.nuaa.handler.ReponseJsonBodyMethodReturnValueHandler">
                <property name="messageConverters">
                    <list>
                        <bean class="com.nuaa.handler.Base64JsonHttpMessageConverter"/>
                    </list>
                </property>
            </bean>
        </mvc:return-value-handlers>
    </mvc:annotation-driven>

 

 

 

 

这个我们可以定义如下的接口，

 

@RequestMapping(value="/addstudentpost", method = RequestMethod.POST,produces="application/json")
@ResponseJsonBody
public Student addstudentpost(@JsonObject Student student,@JsonObject Info info){
     student.setName(JSON.toJSONString(student)+JSON.toJSONString(info)+(new Date()));
     return student;
}

整个函数的定义就比较明了和直观。

 

关于 ResponseJsonBody的注解，请查看http://www.cnblogs.com/wangjiuyong/articles/7162207.html

 

在readme中有测试方法：

http://localhost:8080/spring/controlhandler/addstudentget?student={"name":"zhang","year":100}&info={"address":"yuhuataiqu","city":"nanjing"}


http://localhost:8080/spring/controlhandler/addstudentpost
{
  "student": {
    "name": "wangjiuyong",
    "year": 2000
  },
  "info": {
    "address": "yuhuataiqu",
    "city": "nanjing"
  }
}