Spring MVC控制器方法返回400（错误请求）以响应jQuery ajax请求

Question

I'm sending a jQuery ajax request to a Spring MVC controller method and getting the following response:

 { "timestamp" : "2016-02-10T23:47:14.770+0000",
 "status" : 400,↵  "error" : "Bad Request",
 "exception" : "org.springframework.http.converter.HttpMessageNotReadableException",
"message" : "Bad Request",
"path" : "/chart/add" }

This is the request:

$.ajax({
    type : "POST",
    contentType : "application/json; chartset=utf-8",
    url : "/chart/add",
    data : '{"id":"1","title":"ajax","description":"ajax"}',
    dataType : 'json',
    timeout : 100000,
    success : function(data) {
        console.log("SUCCESS: ", data);
    },
    error : function(e) {
        console.log("ERROR: ", e);
    },
    done : function(e) {
        console.log("DONE");
    }
});

And the following is the spring controller method:

@Controller
public class DatasetController {

    @Autowired private DatasetRepository datasetRepository;
    @Autowired private ChartSpecRepository chartSpecRepository;
    @Autowired private CustomerRepository customerRepository;
    @Autowired private ObjectMapper objectMapper;

    @RequestMapping(value="chart/add", method=RequestMethod.POST)
    public ModelAndView newChart(@RequestBody String json) {
        try {
            ModelAndView ret = new ModelAndView("chart");
            ObjectNode node = objectMapper.readValue(json, ObjectNode.class);
            ChartSpec chart = new ChartSpec();
            NewChartRequest request = objectMapper.convertValue(node, NewChartRequest.class);
            ChartSpec.ChartType chartType = toEnum(request.getChartType());
            String datasetName = request.getDatasetName();
            String customerId = request.getCustomerId();
            Integer bins = request.getBins();
            String[] columns = request.getColumns();
            CustomerDataset dataset = datasetRepository
                .findByCustomerIdAndName(customerId, datasetName);

            chart.setChartType(chartType);
            chart.setDatasetId(dataset.getId());
            chart.setColumns(columns);
            chart.setOptions(request.getOptions());
            chart.setBins(bins);

            if(chartType == ChartSpec.ChartType.HISTOGRAM && bins != null && columns.length > 0) {
                ret.addObject("dataset", histogram(dataset, bins, columns[0]));
            } else if(chartType == ChartSpec.ChartType.BAR && columns.length > 0) {
                ret.addObject("dataset", barChart(dataset, columns[0]));
            } else if(chartType == ChartSpec.ChartType.LINE && columns.length > 2) {
                ret.addObject("dataset", dataset.getColumns(columns[0], columns[1]));
            }

            if(ret.getModel().isEmpty())
                return new ModelAndView("error");

            chartSpecRepository.save(chart);
            return ret;

        } catch(JsonMappingException jme) {
            return new ModelAndView("error");
        } catch(JsonParseException jpe) {
            jpe.printStackTrace();
            return new ModelAndView("error");
        } catch(IOException ioe) {
            return new ModelAndView("error");
        }   
    }
}

The other posts I've seen on this topic seem to revolve around accidentally using @RequestParam instead of @ResquestBody, or not stringifying the JSON. The ajax method above uses literal json instead of the stringified object I intend to use, just to rule out the possibility that the Json is incorrect.

Interestingly, if I use

$.post("/chart/add", '{"id":"1","title":"ajax","description":"ajax"}')

the request goes through. However, I'd like to get a sense of what I'm doing wrong in the ajax method, because I'd like to be able to specify my requests precisely.

Regarding the specific exception thrown, HttpMessageNotReadableException, the Spring documentation says the following:

Thrown by HttpMessageConverter implementations when the HttpMessageConverter.read(java.lang.Class, org.springframework.http.HttpInputMessage) method fails.

However, I don't particularly follow the documentation after that point. Please let me know if I need to provide further information. Any help is appreciated.

Answer 1

Your problem is that you are forcing the content-type in your ajax call.

contentType : "application/json; chartset=utf-8"

As your controller is accepting a String object, the representation is incorrect.

you should either change your @RequestBody String json to a real object, using @RequestBody Document document or remove the content-type from your ajax call

I'd advice creating an object to avoid having to parse the json in your controller

your object could look something like this :

public class Document{
    int id;
    String title;
    String description;
    //getters /setters
}