java - SpringMVC 返回带有 JSON 的对象列表

Question

我有两个选择选项，我希望当用户选择一个选项时，另一个选项会填充数据库中的数据。但是，我在将对象列表返回到 View 时遇到问题。

Controller

@RequestMapping(value="getCrimeTypeList.htm", method = RequestMethod.GET)
 public @ResponseBody List<CrimeType> getCrimeTypeList(@RequestParam(value="crimeCatId") Integer crimeCatId) throws Exception{              

        try {
            List<CrimeType> crimeTypeList = this.crimeTypeManager.getCrimeTypeList(crimeCatId);

             return crimeTypeList;
        } catch (Exception e) {

            logger.error(e.getMessage());
            return null;
        }
}

JQuery

 $("select#offenceCatId").change(function(){

       $.ajax({
           type:'GET',
           url:'getCrimeTypeList.htm',
           data:{crimeCatId: $(this).val()},

            headers: {
             Accept: 'application/json'
            },
           dataType: 'json',

           success:function(data){

            alert('it worked');

           }

       });
     });

HTML

<li>
 <label>Offence Type</label>
 <form:select path="offenceTypeId" id="offenceTypeId" title="Offence Type">
 <form:options items="${crimeType.crimeTypeList}" itemValue="crimeTypeId" itemLabel="crimeTypeDesc"/>
 </form:select>
 <form:errors path="offenceTypeId" class="errors" />
</li>

错误

"NetworkError: 400 Bad Request - http://localhost:8084/crimeTrack/getCrimeTypeList.htm?[object%20Object]"

已编辑我做了一些实验，发现如果 Controller 返回一个字符串，它就可以工作，但是一旦它返回一个对象，我就会遇到问题。

Firebug

GET http://localhost:8084/crimeTrack/getCrimeTypeList.htm?crimeCatId=6 406 Not Acceptable

Response Headers
Content-Length  1067
Content-Type    text/html;charset=utf-8
Date    Fri, 29 Mar 2013 00:58:17 GMT
Server  Apache-Coyote/1.1

Request Headers
Accept  application/json
Accept-Encoding gzip, deflate
Accept-Language en-US,en;q=0.5
Host    localhost:8084
Referer http://localhost:8084/crimeTrack/crime_registration.htm
User-Agent  Mozilla/5.0 (Windows NT 6.1; WOW64; rv:19.0) Gecko/20100101 Firefox/19.0
X-Requested-With    XMLHttpRequest

Answer 1

首先请确保你的 Spring 版本是 3.1.1 版本并且你已经在你的 lib 中添加了 jackson.jar，然后尝试使用下面的代码，你的代码有一些多余的东西。

@RequestMapping(value="/getCrimeTypeList.htm", method = RequestMethod.GET)
public @ResponseBody List<CrimeType> getCrimeTypeList(@RequestParam(value="crimeCatId") Integer crimeCatId) throws Exception{    
            try {
                return this.crimeTypeManager.getCrimeTypeList(crimeCatId);
                //return "true";
            } catch (Exception e) {
                logger.error(e.getMessage());
                return null;
            }
}

$("select#offenceCatId").change(function(){
        var param={crimeCatId:$(this).val()};
        $.ajax({
            type:'GET',
            url:'getCrimeTypeList.htm',
            data:param,
            success:function(data){
                //append options to list
            }
        });
});